I know nothing about how amps work really, and nothing about electronics, but i couldn't help but watch the whole thing. It was super interesting and i liked how you explained everything. Thanks for the good video.
The Guitologist *I've been following you for quite awhile an I learn that the repair of amps, pedals, and speakers requires a very competent and knowledgeable individual as yourself. I've always wanted to ask you; do you except out of state repairs? I'm not judging the amp techs in my area but being in the press industry for 25 years there's nothing like an excellent shop mechanic and being a guitar player that's the way I look at amp technicians. Another great video and thank you for revealing your profession to the masses.*
Thanks for the comment, Mike. I do normally accept out of state repairs as long as you cover shipping both ways. Right now, I'm down to my last couple projects before taking a hiatus from accepting outside repairs. It won't be forever, I just need to catch up on some of my own projects that have been lying around needing attention.
The LDR's and JFET's are the bane of dual rectifiers. It's amazing how you can buy a $2500 amp for $300-$400 that's not working, spend a few bucks for the parts, put a few hours of time fixing it and sell it for 4 times what you bought it for. I guess people are intimidated by the high voltage and parts count of these amps. Or they don't want to take the time learning how to fix stuff. Great video Brad! It's refreshing to see someone fight the throw-away culture.
Retired Automotive Driveability Tech here. Watching you diagnose a fault in the amplifier chassis isn't too different than tracing a fault in a vehicle's engine management system. This knowledge got me a job as a computer tech at Symantec one year when I was injured and couldn't preform my usual job.
What a fix! Love that you know how to hunt down these issues. My neighbor is just like you but doesn’t play. He is a retired Electronics engineer who grew up fixing tube TVs. He is my tech and I’m happy to have someone nearby.
I can't believe that I watched 46 minutes of this without any previous experience on electronics. Sir, you 've got talent and not only with electronics!
I know virtually nothing about electronics, aside from a basic class in high school but for some reason I find your channel strangely satisfying! Lol keep up the rants, I love them too! Thanks
I went to school to be a tech and learned quickly when amp designer/manufacturers went from point to point to PC boards they completely screwed the pooch in an attempt to make them all fancy with the unnecessary bells and whistles. How many fricking circuits does an amp truly need? My 1974 Carvin SS bass amp is point to point. How simple is that? You have far more patience than I but your buddy said the magic words as far as shotgunning all of those FETs. Good job.
I have to say that this was very informative. It does validate my belief that We (I) really don't need a tube amp that has the technology to land an unmanned 747. I will stick with the basic (hand wired, non PC board) tube amp, and buy pedals for anything else I may want. This amp is WAY over engineered. Victoria amps please.
For about the past 20yrs, I have been advertising that I will buy amps, effects, and guitars in any condition, preferably not working. It's been a great source of income. I like the way you work, very proffessional, and you have a great way of explaining your work in layman's terms.
That's one hell of a debugging session! I know nothing of electronics but it was really interesting to observe your methodology of gathering inputs, testing hyphotesis and reaching conclusions up until the amp was back live. Great work!
The mantra at Mesa is, "Can we put an extra part in this amp?" Yeah, Mesa Boogies are much like Corvettes, they're cool when they're running but once they develop issues, they're awfully heavy paperweights. And not every mechanic knows how to work on Vettes and fewer amp guys want to deal with Boogies. Great video!
DUDE! I can't stop watching these videos. I fell into this rabbit hole accidentally one day and have probably watched 20 of them already. Interesting stuff.
Haha me too maybe not 20(yet). This was a rough one, that amp seems to defy probability when running properly. Too bad they didn't make a shitty footboard instead. @The Guitologist, hopefully this one's in a happy home.
As a mechatronics technician and musician I find this video very interesting and useful. Thanks for the effort making the video and going through a very well explanation. I can relate with the feeling of getting frustrated of not finding the failure and the glorious feeling when you finally fix something. Thanks again.
oh absolutely, that the solder earthing the legs on that fet was a real Agatha Christie move. I'm an engineer and amateur repairman myself and found this to be great entertainment. But with all my educational bravado I still don't understand why the MM'S burn out without a load, would think they'd rectify(pun intended) that weakness by now. It's such an easy mistake to do.
The Guitologist I would have to agree with merqury5. This is the most riveting electronics video I've ever seen. I don't know much about electronics but I was fascinated. Well done!
What I find interesting with Mesa Boogie amps is that they have a gain and master knob on each channel, but theres's also a separate output knob that acts like a master volume for all of the channels. I personally love using the output knob as my main master volume. I have this exact same amp, but it's the newest version and it plays and sounds incredible. I absolutely love this amp and I couldn't find myself playing anything else. The key is to find the sound that works for you and write the settings down! If you just move any eq a hair, it will completely change the sound. I love the versatility, but I can completely understand your frustrations with fixing this amp as there's so much shit to look at!!! Hahaha.. Thanks for this video, as I am just a player and have no knowledge of fixing anything electronically, but you look like a super hero figuring this stuff out and whoever designed this amp deserves a medal creating this gem.
I couldn't keep up with most of what this guy was talking about throughout this video, but I'll be damned if I wasn't captivated and interested throughout the entire thing. Really cool stuff!
That cackle after the amplifier first came to life. So satisfying. I have never repaired something that complicated, but the second you let out that laugh I knew the exact feeling. Awesome video!
That was amazing. Thank you for spending the time to show us how you made the fix. I can't believe how much was involved. Also, big props to Boogie for helping out over the phone. I've always had great dealings with them as a company.
Yeah, huge props to George and Rich from Mesa. They were hugely helpful and pointed me in the right direction and were going to send me the service documents had I not already obtained them through the shadow web.
I'm a professional guitarist for the last 35 years and have owned lots of valve amps, Mk1 & MkIV Boogies, a Triaxis, Plexi, JCM800's, Vox's but I don't have a clue how they work, other than to switch it on and turn it up, and I found this fascinating enough to subscribe. Excellent viewing.
If I was the fellow you got the amp from, I'd be very weary of the repair shop he took it too after seeing the leads on the transformer. The damage to the leads look very suspect.
Think about it, the amp would not be in the shop if it had not been damaged already. Maybe the shop could have been more diligent but that problem really would not be seen until you committed to changing the transformer. Not everyone is trying to rip folks off.
Definitely a fair point, which is why I'm slow to point any fingers. The owner did say the shop had broken off those back two knobs which were broken. I was aghast at that alone, so wouldn't surprise me if they ham-fistedly, but not intentionally, chopped the OT leads also.
I do this day in and day out but I find it hard to describe what I'm doing and why.You have an uncanny knack of doing the work,explaining it and filming it!I don't understand why your channel hasn't come up before but now I hang up my iron,switch on youtoob and relax by watching you work it and describe it,finished off with some very nifty fingerwork to show off the completed job.Great work,love the channel.Thanks.
I also don't know the first thing about an amp, the wiring, or these crazy complex boards but I enjoyed every minute of this. Thats for taking the time to do it. I love watching professionals at any craft and learning, although this is so far above my comprehension level I really didn't learn anything. lol but I watched it all. Amazing stuff man and you now have a killer "working" amp for peanuts. Great video.
I have a similar problem, but with a guitar pedal that has a couple of jfets. Same symptoms and result (little to no signal). I haven’t replaced the jfets yet, and I bet that’s where my problem lies. There is a similar “mute” circuit in the pedal, and I bet those jfets are shot. Since it’s a common problem for them to go bad, that’s the first thing I’m gonna replace. Great video, was not expecting to find a very similar problem that I have, great video to stumble across. But I love how you explain everything in this video. Easy to follow along with regardless of camera work.
I have been fortunate enough to watch quite a bit of this kind of repair and yours was no different. Well done! Great trouble shooting! This just goes to show how when "time is money" - how a repair can be so costly because of very inexpensive components failing but creating in depth problems to find. Being able to explain the process is an art! You do it really well! ThankYou! so much for a wonderful repair!
Thank you very much for this video. I repair amps in Sydney and admire your methodical approach to problem solving. I love the sound of a working Mesa amp, but break into a cold sweat when a customer brings one in. :-)
WOW! over my head. This is why I like simple. Mesa is a good product ,but just too many knobs and components for me and way too expensive. I give you credit for your persistence.
Boogie used to put the filter caps in upsidedown in the 80s I had one of the original Mark amps and 3 different techs couldn't figure it out so ended up selling it Guy said he replaced the caps and it was one of the best amp that has come through his shop Crazy I should have sent it to Mesa
Funny thing is, most electrolytic caps do in fact "work" when oriented backwards. By the same token, that's what sucks about them. If you put them in backwards and they are hit with any decent amount of current, they're "formed" internally. And that's that. They're not useable after that, at least in the way they were intended. So they may work, but not correctly. It's like put a chain on your chainsaw on backwards: It will spin, but any cutting is purely from hammering at the wood with brute force and once you've figured it out, your chain is probably trashed.
You have earned your great reputation! It is a slow and monotonous process and yet feels so incredible when you solve the problem. It always amazes me how smart these designers were!
good work and as usual it's the little things that get you crazy. I'm a Mesa guy so they are worth the effort. and the crew are always willing to help. thanks for showing how patient work pays off.
I didn't know anything about the insides of these amps but my ears always tell me to stay away from them! So I'm not surprised to find out that they are not well designed from a circuit analysis perspective
I know this vid is 3 years old but... gosh, what a way to persevere through a repair! :) Something about the fact that a human (albeit a very skilled one) can still make it through such dense, relatively modern circuitry makes me feel... good... for some reason.
Having soldered nothing more than a fuzz pedal and some pickups this stuff is extremely daunting but you make it look easy and give great insight while you're at it. Awesome stuff!
I agree this is one the hardest amp you will find to work on .A couple of notes to mention doing the voltage ratio check on the output transformer is good to determine the turns ratio providing there are no shorted winding and to possibly find a shorted winding. It is not a fool proof test. These transformers usually have around 450 working volts on them and when you add the inductance of the transformer to that you can get some really high voltages which can cause arcing inside a bad transformer. This may not show up until you actually power it up and push it hard. The FET Transistors are to get rid of the popping noise when switching channels. They can be a real pain to find the bad one.
I agree about testing transformers. I was hoping to have learned of some new brilliant way of testing that I had not known... also if it's a step up transformer would it not be better or safer to input into it backwards so you are stepping down instead of stepping up? I have always pondered a better easier and faster way of ruling out a damaged transformer. Especially audio output transformers. I usually test for dc shorts first and then will inject a 2kHz signal @ 100mV into the primary and view the signal on my scope. For the beginner techy wirhout a scope, you can always place a speaker across the secondaries and plug the output of a music player into the primary for a down and dirty quick test of the output transformer and quickly confirm failure or move on to something else.
Those videos are honestly gold mines for those young and amateur "techs" like me who don't mind wastinf time by watching the whole video just to learn a thing or two... or even three.
Wasting time? A huge amount of UA-cam is a waste of time. This is time well spent. People years back knew how to do alot of things & now their grandchildren are morons. I commend you for trying to learn anything constructive.
Since I can no longer tech reliably, living vicariously through you is a good thing. I get some of the same feelings, thanks. Really enjoyed this video.
Very cool video. I work in a guitar shop and we farm out amp repairs to a great local amp tech. We do setups and repairs on guitars, but I never really knew the details on what amp techs do. From my perspective, we give it to a guy who kinda goes off in a cave and comes back with a fixed amp and a twitchy eye. I have two amps that need repair but we keep our dude so busy that I dont want to get in the way of customers' amps. Watching this, now I have a little more perspective on exactly what he's going to have to do. 10/10 would recommend!
Thanks for the hilarious comment. The twitchy eye is a real thing. I think amp techs die of it eventually. One thing amp techs are constantly facing is the repair/replace equation. That can be a difficult tightrope to balance, particularly if you're doing repairs for a shop or shops. Sometimes you put in way more hours than you actually charge because you are trying to keep the arrangement sweet or keep a customer sweet for the shop and not tell them the brand new amp they just bought is actually a total POS basket case that should be replaced rather than repaired.
JalenRawley. Haha, yes, was thinking the xact same thing. Been a pro guit/voc for 30 years, had many an amp repaired, never knew what went on. This opened my eyes, made me realise that these guys really do earn their money.
The case of the cursed head! Thanks brother you just helped me fix two amps I've had in my possession for 5or6 years. I was actually getting ready to junk for parts. I thank you for your channel and will do my best to patron it soon!
THANKS for stepping through for someone who did do bench work 50 years ago but has forgotten so much. Suggest a pointer in place of finger though (with your third hand). Truly, thank you.
When it comes to heat and tubes you can't beat point to point wiring. That's why all of the 1960's tube amps are still standing the test of time. I'm retired now but I used to hate dealing with repairing the newer tube amps with ribbon cables or tube sockets mounted directly to a PCB like you see on a lot of the newer tube amps and before I forget, do not get me started on today's VOX modeling amps.
I thought that at first, but Mesa did actually have a mention of the reverb lead release procedure in the service manual so that tells me it's probably a common thing for someone to think the only way to release the reverb leads is to stick something in there and pry them off. I imagine that's how the leads got severed.
Yes I commented too early while watching, sorry. Later you explain that about the reverb wires/etc. Makes sense now. Between the broken knobs and the cut wires I was thinking at first that someone didn't like it's last owner too much. But hey, awesome video and great explanations of all the madness going on inside that chasis!
Thanks so much for the video! i have an older Triple rectifier that pops between channel switching, and a notably diminished output on the clean channel. If you didn't just pinpoint the problem for me rather precisely, you at least massively pointed me in the right direction. (if memory serves it only pops from channel one (clean) to any other channel, and not all the time, but i rarely play on this amp as it is at my drummer's house as a rehearsal amp). So once again, thank you much. i know jack about amps and electronics, and was really just watching this vid by coincidence to learn some stuff because you demonstrate so well. imagine my surprise halfway through when i was like, "Hey, that's what my rectifier does!"
this type of troubleshooting is still over my head.....im glad I still build clones of old amps and use pedals instead of the complex switching amps of today.
I service guitar amplifiers / equipment myself. This is a great video! I love the way you explain your thought process. Also there are some very useful design and troubleshoot tips in here.
Looks like you are measuring resistance whilst the circuit is powered on, doesn't that invalidate the measurement? The meter is sending a known current through the resistor and measuring the voltage to calculate the resistance. If you power on the amp, it will also be putting current through the resistor and hence the resistance reading will appears to change as it's now reading the external current plus it's measurement current, so the calculation of resistance will be wrong. It could also potentially damage the meter if more than a few volts appears across the resistor you're measuring.
This has been brought up before in other comments. You are correct in general. But even though the amp was powered on, the only current present on the pot I was measuring is the minute signal current. That will not damage any meter, let alone this Fluke. All I was doing really is seeing if the pot was working. That can be done in this particular circuit, and most tube amp circuits, with the amp powered up. The precision of the measurement wasn't paramount. Thanks for the comment!
This is the weirdest design with JFETs I have ever seen. IMHO they are literary *boud to malfunction at some point*, because the method they choosed to switch them On is just wrong! You should never use low impedance to ground to switch p-chanel JFETs, because this way, they are gonna be damaged every time it's drain gets above 1V. If you wanna ensure that they won't be damaged, and you don't wanna rebuild the mute circuit with PNP instead of 6426, add one 4k7 resistor between R128 and colector of NPN 6426 (on the transistor side).
I doubt that :D I am thousands of miles away and I design HW for acces control systems (mostly RFID time-clocks). Building Tube amps is just a hobby. I think that the problem is that more and more engineers design with some simulation programs and they don't test extreme conditions on the real thing. And some engineers are not aware of the fail-modes of basic components, like with those JFETs, you learn how it works under standard conditions (applying positive voltage on gate of p-JFET is going to "shrink" the conductive channel), but ommit the non-standard conditions (if you look at the schematic of JFET, there is an arrow on the gate, which is actual "parasitic"/body diode that shouldn't be ever polarized in conducting direction - and that is what can happen in this design).
You would know better than I. I appreciate you sharing your expertise here. Something to chew on for sure. So your suggested mod for this Mesa Boogie Mute Circuit would be to add one 4k7 resistor between R128 and colector of NPN 6426 (on the transistor side)? And this should lengthen the life of the JFETs?
Yes, if the problem is what I think it is, than it will help protect those JFETs. Also, I checked the numbers once more and I think 470R would be better, since that is sufficient to supress that effect and it won't slow down shutdown of RM2. So I would check this solution, to see if the mute circuit works fine. Other way would be to put those resistors to each gate. What I think happends is that when you try to mute while there is high signal (like when you switch on effect while playing), gates of JFETs are grounded via low resistance of that NPN transitor. Since drain is at high voltage, you will get spike of current going throught the body diode (just until it's muted). Those body diodes are small and can handle only pulse up to 50mA.
mrkv4k and The Guitologist thanks for the video and the conversation. I own a Road King II, a scaled up version of the Roadster, with the opposite problem to yours - it NEVER mutes. As in, i turn all the gain and level knobs down, and there's still room level output on the oversized type 4x12. I would even put a lead into the effects return and leave the other end dangling to make sure the preamp is completely cut off from the effects return and power amp and that hasn't helped either. I thought it might have been the preamp tubes leaking through the high voltage rail to the output tubes, but it would be very involved to decouple that so i haven't tried yet. After watching this video, i ask myself whether it might be the J175's doing this - could they be leaking through the bus that is common to all gates? Maybe signal leaks from the earliest jfets in the signal chain, to the gate bus, then goes to the last jfets in the signal chain, and then back into the signal chain proper to get amplified later? In the configuration used by Mesa, what will the impedance between one of those jfet's gate and the signal path be when the jfet is set to not short (not mute)? Especially if it's a bit "fried" like you say it could be? Bear in mind the muting happens specifically during loud pops so it's like they are trying to kill those jfets. Would you say adding separate 470R or even 4k7 resistors might fix that leak? If i may ask, if you were to redesign the circuit so that this leak doesn't exist, and the components don't self-destruct, how would you do that, and what components would you use? Is there a semiconductor I could use rather than J175's which would provide superior characteristics? If I wanted to find a part like this, what characteristics would i be looking for - would that be gate-source impedance? I freely admit I'm just a layman good with soldering who has the basics of electronics down but I don't have the theoretical background or experience like the both of you do. I've done some good fixes on analog music equipment though (funnily enough had to do with sound leaks, too) so i'm hoping i can get that Mesa fixed up as well.
Great fix! It's always tough when you swap out multiple components at once and still have an issue only to find out that the swap not only fixed the original fault but also introduced another one. Just goes to show that one cannot assume that a component you've replaced is good - it still needs to be checked with everything else.
4k subscribers when this video posted. Im watching this now in 2020 and your going to break 100k subscribers! Excellent channel content and these repairs are very educating . Thank you
This is a great video showing some of the things that go wrong on Mesa amps... I'm sure the road king and V2 will be similar if not other amps from Mesa too. Thanks for posting this as I'm sure that there will be many other guys that will also find it useful.
Could not understand a thing about what you were talking about or pointing out!!!... but I watched to the very end!! I truly wish I had you knowledge of electronics and amps. Thanks for posting, and thanks for inspiring me to self educate myself on the in's and out's of guitar amps.
watching this gave me flashbacks to many Boogie headaches. i no longer work on them. So many features...so many circuit boards. So many jfets. i still have nightmares. somehow watching someone else go through the same thing has been therapeutic. its not just me. thanks
The Roadster is a fantastic amp. If it didn't weigh 100 lbs, I'd still own my Combo. I'm surprised at all the negative comments here on the innards, because to me, it looks like a work of art. It's rare to see a product made so meticulously and beautifully where no one sees it. I see that and it tells me they take pride in their workmanship.
I love watching these types of videos. Maybe one day I can take some kind of course to understand how to do stuff like this. Can someone point me in the right direction? Bye the way awesome video.
Yes, you should subscribe to Uncle Doug's channel as well. Lots of beginner videos explaining basic concepts. You'll learn a lot. Then, come back over to me and you'll understand a lot more of what's going on: ua-cam.com/users/Stratosaurus1
watched the new mesa trouble shoot and repair, got suggested this one figured i could learn some thing,,,,,,,, your so smart im glad to take interest in this stuff and take the countless hours of rec./editing to bring it to us......
Congrats on the millions of hits.Do the same sort of thing but most I on big S/S power amps.Like the channel but I find myself talking to you while I watch.The family thinks I'm loosing it! But at 67,that's allowed.
Brad, I made it to 5:44 and the green wire. THIS is exactly the type thing I find when I work on stuff. My Marshall JMP 50 watt was giving me troubles and when I took it to a tech a friend recommended, he tested it and said my PT was bad. Trusting his results, as he hooked up the meter right in front of me, I bought a Marstran PT and had him install it. Once I went to pick up the amp, he did not return my Original Tranny and claimed he doesn't save stuff like that. That was what would eventually lead to the last time I went to him. I still had to fix the amp myself when it failed ( lost sound) (blew fuses) after that tranny and a cap job. Turns out as I learned amps and was taught many things about diagnosing from internet friends, in London and Australia, I remedied some flaws in the amp, added screed grid resistors, connected wires back where they belonged etc, I had it working and then suddenly no output again. Chopstick tapped everything and when I hit one of the little tabs on the old style Ohms selector, the guitar sound resurfaced thru the speakers. Turns out the female sockets inside were losing contact with the male prongs on the selector cap. Lesson learned, I can fix Amps, Lesson 2, NEVER let any amp tech tell you a vintage part is bad and let them " fix" it until I say thanks, I will now do my own tests and work from now on. Cost me what was likely a multi hundred dollar valuable working 1972 Marshall PT for that lesson.
Actually, I just went by his YT channel, and if you click on his "Discussion" tab, and make it show the most recent entrees, he just left a message to someone 20-minutes ago and several others throughout the week, so he's probably fine.
You sir are a very smart person. I don't have any education in electronics whatsoever but still found this educative even when I couldn't make any sense out of the schematics. Great job.
Thanks for watching. Schematics can be daunting sometimes, especially when you are troubleshooting gear with types of components you aren't used to seeing a lot. I rarely mess with gear that has a lot of ICs or JFETS, for instance, so pages of schematic like the switching matrix take a minute or two to sink into this old brain. ;)
That was a lot of fun watching your video. My first serious job as an adult was an electronic tech after two years of night tech school but that was many many years ago and I have forgot just about everything I had learned. So surprisingly I wasn't lost watching you diagnose and repair the Mesa. Great job!
After 30 years of playing I finally decided to pony up on a serious forever amp. I looked at Mesa, Marshall, Fender.....Divided by 13, three monkeys.....Freidman, Soldano. I studied boutiques and mass production amps for over a year. I've known some Boogie snobs over the last 30 years so I really dove into those because these guys were as high as a crack head on those amps. Needless to say this video really explains mesa and their over engineering. What i ended up with was a Goodsell super 17. Basic. hardwired. Point to point wiring. OSTRICH tolex. All hand made and based of the Hammond organ amplifier. 4 knobs. Reverb (dual spring), gain, tone, volume. It kills. Cleans from heaven and enough gain to get you into hard rock. add a good overdrive pedal and you are screaming creamy leads for days. $1100 used. List price new is no more than the list price for the trash in this video.
Thanks for the comment. I think Mesas such as the Mark V, Roadster, and Road King are for those people who want their, as you say, "forever amp" and want the Swiss Army Knife solution that will, at the press of a footoswitch, do everything they need it to do without a big pedal board full of boutique pedals. I can understand the mentality because, as I've said, I used to be a dealer for Mesa. But I can also understand exactly what you're saying also.
Trash? Hardly, it shouldn't be a surprise that the Mesa has multiple switching circuitry failure modes. The Goodsell has a variety of design issues itself, and from the published photos will be a nightmare to troubleshoot (particularly V3). I certainly wouldn't describe the Goodsell as being better than the Mesa in any way, if anything the Goodsell has a much inferior layout.
It's apples and oranges. The Super 17's point-to-point architecture has nothing in common with a PCB amp philosophically or in terms of execution. Ease of troubleshooting was never a design consideration; one, because it is a ridiculously simple amp, and two, because it has a lifetime warranty and therefore never needs to visit a tech. If it is a matter of customer convenience to use a local guy, then I am happy to do a phone consult, but I do not release schematics to anyone. After individually building nearly 1500 of them, the underbelly of my amps looks like my own calligraphy to me, whereas someone with an eye for the predictable neatness of PCBs might only see spaghetti and chaos. Rest assured there is a method at work. So, inferior to what?
Valve and old tech... has become overrated to a point, would still Prefer it the difference is still very noticeable but I can sacrifice that being super close with stuff now that has a very similar response.
That unit was deliberately sabotaged. I bet there is a nasty personal story behind what went on there. Someone stuck a knife in there on purpose to do this damage. Fantastic video! Learned a lot from your methodical and logical knowledgeable approach to narrowing down the problem. Thanks!
I just knew there would be an utterance of "so something is wrong somewhere" in this video. I almost got it at 23:36. Great video man. Very interesting to even those of us that shouldn't be inside these chassis.
I had this exact issue on my amp. I am no electronics wizard but I was able to fix it. Bought the little JFET things online. They were .49c a piece. Took a while to get up the guts to do it, but it worked out OK and like magic my amp was working again. The fix has held up for about 3 years now and this amp has been gigged a bit. Great video!
Nice demonstration of troubleshooting one of the hardest nuts to crack - the "second opinion" after it's been to another shop. I have had similar experiences of creating a fault while analyzing symptoms - all techs have had the "doh!" moment! :-) very enjoyable 45 minutes!
Damn fine job with the explanation of components, tracing the circuit paths, explanation/demonstration of the schematic, and troubleshooting in a way that was really pleasant to follow. Nicely done, and I look forward to more of your videos!
You can be proud of that job. You are a great example of doing something you love while understanding what you love. Thank you for doing that. Working with you hands and mind.
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I know nothing about how amps work really, and nothing about electronics, but i couldn't help but watch the whole thing. It was super interesting and i liked how you explained everything. Thanks for the good video.
I appreciate you watching and taking time to comment. Lets me know what I'm doing right or wrong.
Eric Altpeter I couldn't have put it better. I also know nothing about both but it was like watching a detective in action. Great video.
The Guitologist *I've been following you for quite awhile an I learn that the repair of amps, pedals, and speakers requires a very competent and knowledgeable individual as yourself. I've always wanted to ask you; do you except out of state repairs? I'm not judging the amp techs in my area but being in the press industry for 25 years there's nothing like an excellent shop mechanic and being a guitar player that's the way I look at amp technicians. Another great video and thank you for revealing your profession to the masses.*
Thanks for the comment, Mike. I do normally accept out of state repairs as long as you cover shipping both ways. Right now, I'm down to my last couple projects before taking a hiatus from accepting outside repairs. It won't be forever, I just need to catch up on some of my own projects that have been lying around needing attention.
Excellent video! Im in the same boat as far as being a novice on electronics or amp repair but got sucked into watching this. Thanks for uploading!
The LDR's and JFET's are the bane of dual rectifiers. It's amazing how you can buy a $2500 amp for $300-$400 that's not working, spend a few bucks for the parts, put a few hours of time fixing it and sell it for 4 times what you bought it for.
I guess people are intimidated by the high voltage and parts count of these amps. Or they don't want to take the time learning how to fix stuff.
Great video Brad! It's refreshing to see someone fight the throw-away culture.
Retired Automotive Driveability Tech here. Watching you diagnose a fault in the amplifier chassis isn't too different than tracing a fault in a vehicle's engine management system. This knowledge got me a job as a computer tech at Symantec one year when I was injured and couldn't preform my usual job.
@@BenState actually it's a real career. But you sound like a made-up troll.
What a fix! Love that you know how to hunt down these issues. My neighbor is just like you but doesn’t play. He is a retired Electronics engineer who grew up fixing tube TVs. He is my tech and I’m happy to have someone nearby.
'Dual Rectumfryer' - That's what my amp tech calls them.
Is your amp tech a foul mouth Canadian with a popular UA-cam channel?
@@iamvillainmo ???
I can't believe that I watched 46 minutes of this without any previous experience on electronics. Sir, you 've got talent and not only with electronics!
I know virtually nothing about electronics, aside from a basic class in high school but for some reason I find your channel strangely satisfying! Lol keep up the rants, I love them too! Thanks
I went to school to be a tech and learned quickly when amp designer/manufacturers went from point to point to PC boards they completely screwed the pooch in an attempt to make them all fancy with the unnecessary bells and whistles. How many fricking circuits does an amp truly need? My 1974 Carvin SS bass amp is point to point. How simple is that?
You have far more patience than I but your buddy said the magic words as far as shotgunning all of those FETs. Good job.
I have to say that this was very informative. It does validate my belief that We (I) really don't need a tube amp that has the technology to land an unmanned 747. I will stick with the basic (hand wired, non PC board) tube amp, and buy pedals for anything else I may want. This amp is WAY over engineered. Victoria amps please.
For about the past 20yrs, I have been advertising that I will buy amps, effects, and guitars in any condition, preferably not working. It's been a great source of income.
I like the way you work, very proffessional, and you have a great way of explaining your work in layman's terms.
Tons of respect for digging into that monster, and your perseverance in rooting out the problem!
Be it ever so humble, 4k turned into over 100k within 2 years! I really enjoy your mix of repair vids brother.
Thanks Phillip.
That's one hell of a debugging session! I know nothing of electronics but it was really interesting to observe your methodology of gathering inputs, testing hyphotesis and reaching conclusions up until the amp was back live. Great work!
The mantra at Mesa is, "Can we put an extra part in this amp?" Yeah, Mesa Boogies are much like Corvettes, they're cool when they're running but once they develop issues, they're awfully heavy paperweights. And not every mechanic knows how to work on Vettes and fewer amp guys want to deal with Boogies. Great video!
DUDE! I can't stop watching these videos. I fell into this rabbit hole accidentally one day and have probably watched 20 of them already. Interesting stuff.
Haha me too maybe not 20(yet). This was a rough one, that amp seems to defy probability when running properly. Too bad they didn't make a shitty footboard instead. @The Guitologist, hopefully this one's in a happy home.
As a mechatronics technician and musician I find this video very interesting and useful. Thanks for the effort making the video and going through a very well explanation. I can relate with the feeling of getting frustrated of not finding the failure and the glorious feeling when you finally fix something. Thanks again.
To me that was a bonefied thriller with a plot twist at the end. Massively impressive.
That's the first time I've heard one of my videos described as a "thriller" with a "plot twist" Feels kinda good to hear that. Thanks!
oh absolutely, that the solder earthing the legs on that fet was a real Agatha Christie move. I'm an engineer and amateur repairman myself and found this to be great entertainment. But with all my educational bravado I still don't understand why the MM'S burn out without a load, would think they'd rectify(pun intended) that weakness by now. It's such an easy mistake to do.
The Guitologist I would have to agree with merqury5. This is the most riveting electronics video I've ever seen. I don't know much about electronics but I was fascinated. Well done!
Spoiler alert. lol
Bona-fide. It's a borrowed word in English, from one of the Latin languages. Rough translation "good - faithful"
What I find interesting with Mesa Boogie amps is that they have a gain and master knob on each channel, but theres's also a separate output knob that acts like a master volume for all of the channels. I personally love using the output knob as my main master volume. I have this exact same amp, but it's the newest version and it plays and sounds incredible. I absolutely love this amp and I couldn't find myself playing anything else. The key is to find the sound that works for you and write the settings down! If you just move any eq a hair, it will completely change the sound. I love the versatility, but I can completely understand your frustrations with fixing this amp as there's so much shit to look at!!! Hahaha.. Thanks for this video, as I am just a player and have no knowledge of fixing anything electronically, but you look like a super hero figuring this stuff out and whoever designed this amp deserves a medal creating this gem.
I couldn't keep up with most of what this guy was talking about throughout this video, but I'll be damned if I wasn't captivated and interested throughout the entire thing. Really cool stuff!
That cackle after the amplifier first came to life. So satisfying. I have never repaired something that complicated, but the second you let out that laugh I knew the exact feeling. Awesome video!
That was amazing. Thank you for spending the time to show us how you made the fix. I can't believe how much was involved. Also, big props to Boogie for helping out over the phone. I've always had great dealings with them as a company.
Yeah, huge props to George and Rich from Mesa. They were hugely helpful and pointed me in the right direction and were going to send me the service documents had I not already obtained them through the shadow web.
I'm a professional guitarist for the last 35 years and have owned lots of valve amps, Mk1 & MkIV Boogies, a Triaxis, Plexi, JCM800's, Vox's but I don't have a clue how they work, other than to switch it on and turn it up, and I found this fascinating enough to subscribe. Excellent viewing.
If I was the fellow you got the amp from, I'd be very weary of the repair shop he took it too after seeing the leads on the transformer. The damage to the leads look very suspect.
Think about it, the amp would not be in the shop if it had not been damaged already. Maybe the shop could have been more diligent but that problem really would not be seen until you committed to changing the transformer. Not everyone is trying to rip folks off.
Definitely a fair point, which is why I'm slow to point any fingers. The owner did say the shop had broken off those back two knobs which were broken. I was aghast at that alone, so wouldn't surprise me if they ham-fistedly, but not intentionally, chopped the OT leads also.
Took it in for the bad components, broke the wires opening it up and assumed that was the problem all along?
Appears that way. Seems to be the most logical answer.
Suspect? That damage is 100% from a cutting plier
An accidental solder bridge can be a bugger, but it sure feels great when you get something like this back to its former glory!
I do this day in and day out but I find it hard to describe what I'm doing and why.You have an uncanny knack of doing the work,explaining it and filming it!I don't understand why your channel hasn't come up before but now I hang up my iron,switch on youtoob and relax by watching you work it and describe it,finished off with some very nifty fingerwork to show off the completed job.Great work,love the channel.Thanks.
thanks a lot, john.
I also don't know the first thing about an amp, the wiring, or these crazy complex boards but I enjoyed every minute of this. Thats for taking the time to do it. I love watching professionals at any craft and learning, although this is so far above my comprehension level I really didn't learn anything. lol but I watched it all. Amazing stuff man and you now have a killer "working" amp for peanuts. Great video.
I have a similar problem, but with a guitar pedal that has a couple of jfets. Same symptoms and result (little to no signal). I haven’t replaced the jfets yet, and I bet that’s where my problem lies. There is a similar “mute” circuit in the pedal, and I bet those jfets are shot. Since it’s a common problem for them to go bad, that’s the first thing I’m gonna replace. Great video, was not expecting to find a very similar problem that I have, great video to stumble across. But I love how you explain everything in this video. Easy to follow along with regardless of camera work.
I have been fortunate enough to watch quite a bit of this kind of repair and yours was no different. Well done! Great trouble shooting! This just goes to show how when "time is money" - how a repair can be so costly because of very inexpensive components failing but creating in depth problems to find. Being able to explain the process is an art! You do it really well! ThankYou! so much for a wonderful repair!
Thank you very much for this video. I repair amps in Sydney and admire your methodical approach to problem solving. I love the sound of a working Mesa amp, but break into a cold sweat when a customer brings one in. :-)
The gods thrive on tech tears.
WOW! over my head. This is why I like simple. Mesa is a good product ,but just too many knobs and components for me and way too expensive. I give you credit for your persistence.
Nice work Brad, and what a great find. You put a lot of Amp Techs to shame.
I loved your clear , open communication as you walk us through your diagnosis process from start to finish . Subscribed ! Just excellent !
Boogie used to put the filter caps in upsidedown in the 80s I had one of the original Mark amps and 3 different techs couldn't figure it out so ended up selling it Guy said he replaced the caps and it was one of the best amp that has come through his shop Crazy I should have sent it to Mesa
Funny thing is, most electrolytic caps do in fact "work" when oriented backwards. By the same token, that's what sucks about them. If you put them in backwards and they are hit with any decent amount of current, they're "formed" internally. And that's that. They're not useable after that, at least in the way they were intended. So they may work, but not correctly. It's like put a chain on your chainsaw on backwards: It will spin, but any cutting is purely from hammering at the wood with brute force and once you've figured it out, your chain is probably trashed.
You have earned your great reputation! It is a slow and monotonous process and yet feels so incredible when you solve the problem. It always amazes me how smart these designers were!
good work and as usual it's the little things that get you crazy. I'm a Mesa guy so they are worth the effort. and the crew are always willing to help. thanks for showing how patient work pays off.
Yep, as I said in the vid, Mesa Customer Service is tip top.
I didn't know anything about the insides of these amps but my ears always tell me to stay away from them! So I'm not surprised to find out that they are not well designed from a circuit analysis perspective
Geez what a journey through some complex trouble-shooting! Amazing!
I know this vid is 3 years old but... gosh, what a way to persevere through a repair! :) Something about the fact that a human (albeit a very skilled one) can still make it through such dense, relatively modern circuitry makes me feel... good... for some reason.
Good description of how depletion mode JFETs function.
I am by no means an expert on semiconductors, but I know enough to get into trouble.
Having soldered nothing more than a fuzz pedal and some pickups this stuff is extremely daunting but you make it look easy and give great insight while you're at it. Awesome stuff!
Thanks for watching and commenting. Much appreciated.
I agree this is one the hardest amp you will find to work on .A couple of notes to mention doing the voltage ratio check on the output transformer is good to determine the turns ratio providing there are no shorted winding and to possibly find a shorted winding. It is not a fool proof test. These transformers usually have around 450 working volts on them and when you add the inductance of the transformer to that you can get some really high voltages which can cause arcing inside a bad transformer. This may not show up until you actually power it up and push it hard.
The FET Transistors are to get rid of the popping noise when switching channels. They can be a real pain to find the bad one.
I agree about testing transformers. I was hoping to have learned of some new brilliant way of testing that I had not known... also if it's a step up transformer would it not be better or safer to input into it backwards so you are stepping down instead of stepping up? I have always pondered a better easier and faster way of ruling out a damaged transformer. Especially audio output transformers. I usually test for dc shorts first and then will inject a 2kHz signal @ 100mV into the primary and view the signal on my scope.
For the beginner techy wirhout a scope, you can always place a speaker across the secondaries and plug the output of a music player into the primary for a down and dirty quick test of the output transformer and quickly confirm failure or move on to something else.
Those videos are honestly gold mines for those young and amateur "techs" like me who don't mind wastinf time by watching the whole video just to learn a thing or two... or even three.
Wasting time?
A huge amount of UA-cam is a waste of time. This is time well spent. People years back knew how to do alot of things & now their grandchildren are morons.
I commend you for trying to learn anything constructive.
Thanks for the explanation in the comments. Really appreciate your thorough videos. Always good to hear them played at the end.
Since I can no longer tech reliably, living vicariously through you is a good thing. I get some of the same feelings, thanks. Really enjoyed this video.
Very cool video. I work in a guitar shop and we farm out amp repairs to a great local amp tech. We do setups and repairs on guitars, but I never really knew the details on what amp techs do. From my perspective, we give it to a guy who kinda goes off in a cave and comes back with a fixed amp and a twitchy eye. I have two amps that need repair but we keep our dude so busy that I dont want to get in the way of customers' amps. Watching this, now I have a little more perspective on exactly what he's going to have to do. 10/10 would recommend!
Thanks for the hilarious comment. The twitchy eye is a real thing. I think amp techs die of it eventually. One thing amp techs are constantly facing is the repair/replace equation. That can be a difficult tightrope to balance, particularly if you're doing repairs for a shop or shops. Sometimes you put in way more hours than you actually charge because you are trying to keep the arrangement sweet or keep a customer sweet for the shop and not tell them the brand new amp they just bought is actually a total POS basket case that should be replaced rather than repaired.
JalenRawley. Haha, yes, was thinking the xact same thing. Been a pro guit/voc for 30 years, had many an amp repaired, never knew what went on.
This opened my eyes, made me realise that these guys really do earn their money.
The case of the cursed head! Thanks brother you just helped me fix two amps I've had in my possession for 5or6 years. I was actually getting ready to junk for parts. I thank you for your channel and will do my best to patron it soon!
They may be a pain to work on but I sure love playing through my Roadster.
Hard agree. Until it stopped working. I'm terrified to take it in. I know a very good amp guy and he absolutely HATES working on Mesas.
THANKS for stepping through for someone who did do bench work 50 years ago but has forgotten so much. Suggest a pointer in place of finger though (with your third hand).
Truly, thank you.
When it comes to heat and tubes you can't beat point to point wiring. That's why all of the 1960's tube amps are still standing the test of time. I'm retired now but I used to hate dealing with repairing the newer tube amps with ribbon cables or tube sockets mounted directly to a PCB like you see on a lot of the newer tube amps and before I forget, do not get me started on today's VOX modeling amps.
Nothing like that feeling of getting a circuit figured out. Great job.
Yeah, this one felt good to get right. Intimidating when you first pop the hood on one of these.
Looks like someone took a razor knife to that transformer wire. That's seriously shady.
I thought that at first, but Mesa did actually have a mention of the reverb lead release procedure in the service manual so that tells me it's probably a common thing for someone to think the only way to release the reverb leads is to stick something in there and pry them off. I imagine that's how the leads got severed.
Yes I commented too early while watching, sorry. Later you explain that about the reverb wires/etc. Makes sense now. Between the broken knobs and the cut wires I was thinking at first that someone didn't like it's last owner too much. But hey, awesome video and great explanations of all the madness going on inside that chasis!
Thanks so much for the video! i have an older Triple rectifier that pops between channel switching, and a notably diminished output on the clean channel. If you didn't just pinpoint the problem for me rather precisely, you at least massively pointed me in the right direction. (if memory serves it only pops from channel one (clean) to any other channel, and not all the time, but i rarely play on this amp as it is at my drummer's house as a rehearsal amp). So once again, thank you much. i know jack about amps and electronics, and was really just watching this vid by coincidence to learn some stuff because you demonstrate so well. imagine my surprise halfway through when i was like, "Hey, that's what my rectifier does!"
Replace all those JFETs, man. That should fix it. Just don't screw up and short the leads like I did! :)
this type of troubleshooting is still over my head.....im glad I still build clones of old amps and use pedals instead of the complex switching amps of today.
Great vid, Had the JFET's go out in my RdKing head. All it took was one of our great lightning storms here in Tampa & I was on mute madness..
I'll stick with my Marshall JCM800 combo. BJT all the way on the electronics.
George at Mesa, fine fellow. Talked with and learned much from him many times over that last two decades. Happy retirement, George.
I service guitar amplifiers / equipment myself.
This is a great video! I love the way you explain your thought process.
Also there are some very useful design and troubleshoot tips in here.
Thanks for that. Appreciate the comment!
I don't know how this came through my feed, but I appreciate a good troubleshooting video.
Looks like you are measuring resistance whilst the circuit is powered on, doesn't that invalidate the measurement? The meter is sending a known current through the resistor and measuring the voltage to calculate the resistance. If you power on the amp, it will also be putting current through the resistor and hence the resistance reading will appears to change as it's now reading the external current plus it's measurement current, so the calculation of resistance will be wrong. It could also potentially damage the meter if more than a few volts appears across the resistor you're measuring.
This has been brought up before in other comments. You are correct in general. But even though the amp was powered on, the only current present on the pot I was measuring is the minute signal current. That will not damage any meter, let alone this Fluke. All I was doing really is seeing if the pot was working. That can be done in this particular circuit, and most tube amp circuits, with the amp powered up. The precision of the measurement wasn't paramount. Thanks for the comment!
I'm a Boogie man. Yes... the Mark 5, etc... insane complexity. Thumbs up to you for your patience. Wow! And yes... Mesa has always had great service.
This is the weirdest design with JFETs I have ever seen. IMHO they are literary *boud to malfunction at some point*, because the method they choosed to switch them On is just wrong!
You should never use low impedance to ground to switch p-chanel JFETs, because this way, they are gonna be damaged every time it's drain gets above 1V.
If you wanna ensure that they won't be damaged, and you don't wanna rebuild the mute circuit with PNP instead of 6426, add one 4k7 resistor between R128 and colector of NPN 6426 (on the transistor side).
Maybe there's a job at Mesa in your future.
I doubt that :D I am thousands of miles away and I design HW for acces control systems (mostly RFID time-clocks). Building Tube amps is just a hobby.
I think that the problem is that more and more engineers design with some simulation programs and they don't test extreme conditions on the real thing. And some engineers are not aware of the fail-modes of basic components, like with those JFETs, you learn how it works under standard conditions (applying positive voltage on gate of p-JFET is going to "shrink" the conductive channel), but ommit the non-standard conditions (if you look at the schematic of JFET, there is an arrow on the gate, which is actual "parasitic"/body diode that shouldn't be ever polarized in conducting direction - and that is what can happen in this design).
You would know better than I. I appreciate you sharing your expertise here. Something to chew on for sure. So your suggested mod for this Mesa Boogie Mute Circuit would be to add one 4k7 resistor between R128 and colector of NPN 6426 (on the transistor side)? And this should lengthen the life of the JFETs?
Yes, if the problem is what I think it is, than it will help protect those JFETs. Also, I checked the numbers once more and I think 470R would be better, since that is sufficient to supress that effect and it won't slow down shutdown of RM2. So I would check this solution, to see if the mute circuit works fine. Other way would be to put those resistors to each gate.
What I think happends is that when you try to mute while there is high signal (like when you switch on effect while playing), gates of JFETs are grounded via low resistance of that NPN transitor. Since drain is at high voltage, you will get spike of current going throught the body diode (just until it's muted). Those body diodes are small and can handle only pulse up to 50mA.
mrkv4k and The Guitologist thanks for the video and the conversation. I own a Road King II, a scaled up version of the Roadster, with the opposite problem to yours - it NEVER mutes. As in, i turn all the gain and level knobs down, and there's still room level output on the oversized type 4x12. I would even put a lead into the effects return and leave the other end dangling to make sure the preamp is completely cut off from the effects return and power amp and that hasn't helped either. I thought it might have been the preamp tubes leaking through the high voltage rail to the output tubes, but it would be very involved to decouple that so i haven't tried yet. After watching this video, i ask myself whether it might be the J175's doing this - could they be leaking through the bus that is common to all gates? Maybe signal leaks from the earliest jfets in the signal chain, to the gate bus, then goes to the last jfets in the signal chain, and then back into the signal chain proper to get amplified later? In the configuration used by Mesa, what will the impedance between one of those jfet's gate and the signal path be when the jfet is set to not short (not mute)? Especially if it's a bit "fried" like you say it could be? Bear in mind the muting happens specifically during loud pops so it's like they are trying to kill those jfets. Would you say adding separate 470R or even 4k7 resistors might fix that leak? If i may ask, if you were to redesign the circuit so that this leak doesn't exist, and the components don't self-destruct, how would you do that, and what components would you use? Is there a semiconductor I could use rather than J175's which would provide superior characteristics? If I wanted to find a part like this, what characteristics would i be looking for - would that be gate-source impedance? I freely admit I'm just a layman good with soldering who has the basics of electronics down but I don't have the theoretical background or experience like the both of you do. I've done some good fixes on analog music equipment though (funnily enough had to do with sound leaks, too) so i'm hoping i can get that Mesa fixed up as well.
Great fix! It's always tough when you swap out multiple components at once and still have an issue only to find out that the swap not only fixed the original fault but also introduced another one. Just goes to show that one cannot assume that a component you've replaced is good - it still needs to be checked with everything else.
I would never have the patience for this shit. Great job man. I’m hooked on watching you do it though.
Welcome aboard, Dan.
4k subscribers when this video posted. Im watching this now in 2020 and your going to break 100k subscribers! Excellent channel content and these repairs are very educating . Thank you
I would try this but I would need life insurance first, electricity likes me.....great video can't believe I'm watching this I play drums!
I guess it's truly a good video if I can maintain a drummer's interest longer than 60 seconds. :P
Lol
Nice job! It's rare to see a young person know something about trouble shooting circuits.
This is a great video showing some of the things that go wrong on Mesa amps... I'm sure the road king and V2 will be similar if not other amps from Mesa too. Thanks for posting this as I'm sure that there will be many other guys that will also find it useful.
Not many Mesa service videos up really. I hope others do find it useful.
The Guitologist this gave me ideas on how to fix an RKII i've been trying to fix for at least a year! Thanks a lot!
I still want one of these in any (working) configuration.
Always informative AND entertaining...I have now watched this twice.
I know this is old but, nice work!
As a non-tech type, I didn't understand the technical side but really enjoyed the process. Awesome.
I really enjoyed watching this! And I have learned a lot of things in the process. Thanks!
Could not understand a thing about what you were talking about or pointing out!!!... but I watched to the very end!! I truly wish I had you knowledge of electronics and amps. Thanks for posting, and thanks for inspiring me to self educate myself on the in's and out's of guitar amps.
used to do this type of thing back in the late 80's, thoroughly enjoyed watching this :)
I'm not an amp builder, maybe some day, but so far i made some pedals, although nothing mega complex, and this channel is somewhat enjoyable to watch.
those .25 cent parts will always get ya
Absolutely.
watching this gave me flashbacks to many Boogie headaches. i no longer work on them. So many features...so many circuit boards. So many jfets. i still have nightmares. somehow watching someone else go through the same thing has been therapeutic. its not just me. thanks
Who can dislike this video???? Man the haters are way out of control. Great job I really enjoy this video.
The Roadster is a fantastic amp. If it didn't weigh 100 lbs, I'd still own my Combo. I'm surprised at all the negative comments here on the innards, because to me, it looks like a work of art. It's rare to see a product made so meticulously and beautifully where no one sees it. I see that and it tells me they take pride in their workmanship.
I love watching these types of videos. Maybe one day I can take some kind of course to understand how to do stuff like this. Can someone point me in the right direction? Bye the way awesome video.
Yes, you should subscribe to Uncle Doug's channel as well. Lots of beginner videos explaining basic concepts. You'll learn a lot. Then, come back over to me and you'll understand a lot more of what's going on: ua-cam.com/users/Stratosaurus1
watched the new mesa trouble shoot and repair, got suggested this one figured i could learn some thing,,,,,,,, your so smart im glad to take interest in this stuff and take the countless hours of rec./editing to bring it to us......
I dislike the Messy Boogers. Nice work on the OT there. ;-)
I considered that a huge win considering the previous "tech" had told the customer it was hopelessly bad and tried to sell him a $300+ Mercury.
I call WIN.
Congrats on the millions of hits.Do the same sort of thing but most I on big S/S power amps.Like the channel but I find myself talking to you while I watch.The family thinks I'm loosing it! But at 67,that's allowed.
I watched just about all of it! Love your content
Brad, I made it to 5:44 and the green wire. THIS is exactly the type thing I find when I work on stuff. My Marshall JMP 50 watt was giving me troubles and when I took it to a tech a friend recommended, he tested it and said my PT was bad. Trusting his results, as he hooked up the meter right in front of me, I bought a Marstran PT and had him install it. Once I went to pick up the amp, he did not return my Original Tranny and claimed he doesn't save stuff like that. That was what would eventually lead to the last time I went to him. I still had to fix the amp myself when it failed ( lost sound) (blew fuses) after that tranny and a cap job. Turns out as I learned amps and was taught many things about diagnosing from internet friends, in London and Australia, I remedied some flaws in the amp, added screed grid resistors, connected wires back where they belonged etc, I had it working and then suddenly no output again. Chopstick tapped everything and when I hit one of the little tabs on the old style Ohms selector, the guitar sound resurfaced thru the speakers. Turns out the female sockets inside were losing contact with the male prongs on the selector cap. Lesson learned, I can fix Amps, Lesson 2, NEVER let any amp tech tell you a vintage part is bad and let them " fix" it until I say thanks, I will now do my own tests and work from now on. Cost me what was likely a multi hundred dollar valuable working 1972 Marshall PT for that lesson.
Have you seen anything of Uncle Doug? He's been AWOL for quite some time now.
Bill Seper good question. No I have not. I've missed him.
He hasn't put up a video in 5 months, but he did leave a post on his FB page about two months ago, so I think he must be taking some time off.
Actually, I just went by his YT channel, and if you click on his "Discussion" tab, and make it show the most recent entrees, he just left a message to someone 20-minutes ago and several others throughout the week, so he's probably fine.
I love that guy. I hope all is well.
...I am Doug....I'm here and OK...!
Nice work. The sort of amp I wouldn't dare touch and you fought your way through it.
Interesting video dude!
You sir are a very smart person. I don't have any education in electronics whatsoever but still found this educative even when I couldn't make any sense out of the schematics. Great job.
Thanks for watching. Schematics can be daunting sometimes, especially when you are troubleshooting gear with types of components you aren't used to seeing a lot. I rarely mess with gear that has a lot of ICs or JFETS, for instance, so pages of schematic like the switching matrix take a minute or two to sink into this old brain. ;)
Can you still pay with peanuts on Craigslist? I know a lot of users have moved to the more user-friendly PeanutPal, ho ho.
PeanutCoin
The Guitologist hahahaha
Salted or unsalted?
Dees Nuts?
That was a lot of fun watching your video. My first serious job as an adult was an electronic tech after two years of night tech school but that was many many years ago and I have forgot just about everything I had learned. So surprisingly I wasn't lost watching you diagnose and repair the Mesa. Great job!
It's amazing how quickly stuff will come back to you after not using it for years or decades.
After 30 years of playing I finally decided to pony up on a serious forever amp. I looked at Mesa, Marshall, Fender.....Divided by 13, three monkeys.....Freidman, Soldano. I studied boutiques and mass production amps for over a year. I've known some Boogie snobs over the last 30 years so I really dove into those because these guys were as high as a crack head on those amps.
Needless to say this video really explains mesa and their over engineering. What i ended up with was a Goodsell super 17. Basic. hardwired. Point to point wiring. OSTRICH tolex. All hand made and based of the Hammond organ amplifier. 4 knobs. Reverb (dual spring), gain, tone, volume. It kills. Cleans from heaven and enough gain to get you into hard rock. add a good overdrive pedal and you are screaming creamy leads for days. $1100 used. List price new is no more than the list price for the trash in this video.
Thanks for the comment. I think Mesas such as the Mark V, Roadster, and Road King are for those people who want their, as you say, "forever amp" and want the Swiss Army Knife solution that will, at the press of a footoswitch, do everything they need it to do without a big pedal board full of boutique pedals. I can understand the mentality because, as I've said, I used to be a dealer for Mesa. But I can also understand exactly what you're saying also.
Trash? Hardly, it shouldn't be a surprise that the Mesa has multiple switching circuitry failure modes. The Goodsell has a variety of design issues itself, and from the published photos will be a nightmare to troubleshoot (particularly V3). I certainly wouldn't describe the Goodsell as being better than the Mesa in any way, if anything the Goodsell has a much inferior layout.
It's apples and oranges. The Super 17's point-to-point architecture has nothing in common with a PCB amp philosophically or in terms of execution. Ease of troubleshooting was never a design consideration; one, because it is a ridiculously simple amp, and two, because it has a lifetime warranty and therefore never needs to visit a tech. If it is a matter of customer convenience to use a local guy, then I am happy to do a phone consult, but I do not release schematics to anyone. After individually building nearly 1500 of them, the underbelly of my amps looks like my own calligraphy to me, whereas someone with an eye for the predictable neatness of PCBs might only see spaghetti and chaos. Rest assured there is a method at work. So, inferior to what?
I've seen the inside of a Super 17. Looks pretty serviceable to me. Roomy compared to the amps I've built.
Valve and old tech... has become overrated to a point, would still Prefer it the difference is still very noticeable but I can sacrifice that being super close with stuff now that has a very similar response.
That unit was deliberately sabotaged. I bet there is a nasty personal story behind what went on there. Someone stuck a knife in there on purpose to do this damage. Fantastic video! Learned a lot from your methodical and logical knowledgeable approach to narrowing down the problem. Thanks!
Ahh, Mesa Boogie. Overpriced, overweight and over complicated.
But still bought in masses...
The overweight thing is the reason why I never bought one. After watching this video, I realize that avoiding Mesa Boogie was a blessing.
Nah, Boogies are great. Got the Mark V and the Road King 2 and they’re some of the best amps I’ve played. I’ve played most stuff.
I just knew there would be an utterance of "so something is wrong somewhere" in this video. I almost got it at 23:36. Great video man. Very interesting to even those of us that shouldn't be inside these chassis.
43:53 Emperor laugh.
Translated: "I got you, you *itch."
I had this exact issue on my amp. I am no electronics wizard but I was able to fix it. Bought the little JFET things online. They were .49c a piece. Took a while to get up the guts to do it, but it worked out OK and like magic my amp was working again. The fix has held up for about 3 years now and this amp has been gigged a bit. Great video!
Thanks for sharing, I wish I had UA-cam and channel like this back in the 90' when I was study electronics.
Nice demonstration of troubleshooting one of the hardest nuts to crack - the "second opinion" after it's been to another shop. I have had similar experiences of creating a fault while analyzing symptoms - all techs have had the "doh!" moment! :-) very enjoyable 45 minutes!
Damn fine job with the explanation of components, tracing the circuit paths, explanation/demonstration of the schematic, and troubleshooting in a way that was really pleasant to follow.
Nicely done, and I look forward to more of your videos!
Nice of you to say, Chris. Thanks.
Have never, nor have any intention of touching electronics but I watched this whole thing and found it fascinating, Nice job!
You can be proud of that job. You are a great example of doing something you love while understanding what you love. Thank you for doing that. Working with you hands and mind.