You are one of my favorite amp techs and always teach me so much. I really appreciate all of your work. I can only hope that I find a local mentor like you someday, you're a bit far from Chicago.
Dear Chris, It's great that you brought this beast back on stage. Every guitarist is lucky to have you as a tech. I just read in one of your posts that your daughter is very weak at the moment and the operation is imminent. I am thinking of you and praying for your daughter. I myself lost my father to this terrible disease last week and know what you are going through. Best wishes from Germany Markus🙏♥🕯
Guten Morgen, mein Freund from Köln. You are very kind. I am so sad about you losing your father. My father also went from pancreatic cancer. What a horrible disease this is. The surgeon and oncologist are expecting a full recovery for my daughter, but the journey is so hard. So much pain.
Many thanks for these two videos on the Mesa Boogie Mk1. I discovered them at just the right time as I had my first boogie on the bench, having not had one for repair or service before . Your two videos helped me a great deal. I agree with all the points you highlighted. What a contrast with Fender who are unafraid to share their schematics and even PCB layout and test point values. Once again thanks
Thank you, Stephen. I have made a commitment to myself (and those who care for my physical and mental health!) that I will not accept any more Mesa amps to work on. They are just not worth the angst. I feel sorry for those customers who fell for their hype, but its not my journey.
I don't recall if I showed the plague of dry joints. They were doing my head in. In the end the only way was to suck out all of previous Techs solder and replace it with quality solder.
I would never usually watch any kind of a Boogie repair video, but I like your patient, thorough and electrical safety minded style Chris. Great job on that thing, I'm sure it's the best it sounded in many years, if not ever. I like simple, effective tools, so I'd definitely be interested in your capacitor leakage tester specs, btw. I Usually just lift the end opposite the plates and make sure its completely void of any DC whatsoever. I expected more crossover distortion too, than appeared on your scope, interesting. Randall supposedly purposely adds mistakes in some of his schematics btw, I'm told, so beware in the future. Best of luck with your daughter too.
That's the way I used to measure leakage, too, but the input impedance of a good DMM is so high that it poses no load on the grid side of the coupling cap to highlight any leakage. I'd be interested to see if the DMMs with a Low Z setting may sniff out the leaky caps. If you have such a meter, please let me know if it works. I will build a LED Leakage Tester Mark 2 when I can see daylight again. The situation with my daughter is of course a priority. Thankfully my customers are understanding and patient. If Mark 2 works well, I'll post a video on it.
Another magnificent video Chris..! I always learn so much from what I call a treat..! Great info and explanations of the AB type of amps etc..You're a star man.! Hope your family is doing well mate..Ed..uk..😁
Thanks Ed! Its always good to see your comments at the start of my day. My daughter has now had the double mastectomy. She'll be leaving hospital tomorrow and then we hold our breath for the biopsy result. Thanks for asking!
@@moodyga40 maybe I should try it next time (hopefully never) that I need to work on a Mesa. In fact, a rollie of Petaluma weed may help get inside the mind of Mr Smith.
Really enjoy your videos. You have a way of explaining things that is filling in some of the gaps in my vary limited tube amp knowledge. I''d enjoy a video going over the reasons behind "hot" cathode biasing power tubes like in the VOX and in my Friedman Little Sister. Your thoughts on using a Variac and selecting tubes by spec to possibly increase tube life or just find the sweet spot tonally.
Thank you, Kent. I appreciate your kind words. The main reason why a variac is not the ideal solution for cooling down an amp, is that it will also have an effect on your filament voltage. Too high or too low a filament voltage may shorten tube life. A good rule of thumb is +/- 10% Max variation.
Hi Chris .........I enjoy your expertise combined with wit and wisdom. I have a Mark 1 RI sitting in the bedroom / music room of my home out here in the sticks of the deep south. I have wanted one for decades and finally have a real beauty with the wicker / cane speaker "cloth". It's the 100 / 60. I thought the reverb was rather weak so I replaced the 12 T7 tube with a new one which helped . Even with the reverb up all the way, it's just "ok".......nothing like a "surf" Fender reverb, which I didn't really expect it to be.......however, is there anything I can have done that might improve it ? Thank you Jim Muscle Shoals, AL
Hi Jim. Wow. Muscle Shoals. Its on my bucket list. I just want to lean up against the wall outside the studio for a cool-dude photo and pretend I am someone I'm not. Good question. As you know there are 4 parts to a Reverb circuit, the driver tube, the reverb transformer, the reverb tank and the recovery tube. Any one of those elements could be your issue. Fender uses both triodes of a 12AT7 to drive the reverb transformer, whereas the Mesa uses one triode. I would not expect your sound to hit the reverb tank as hard. Good luck.
@@theguitaramptech Thanks.....do you it might make a difference by putting in a 12AX7 instead of the 12AT7? BTW........it's pretty neat to take the tour of FAME studios and listen to some master tapes going through their studio monitors. Being from the north, I have a hard time during the summer months here, but I do enjoy the music history.
Hello.. great and informative video series… Just wondering if you used a regular passive probe to scope the output..? And whether you scoped the single at the speaker terminals or power tube output..? possibly a differential probe..?
Yes, I use a passive probe, usually in the 10X position for less loading and improved bandwidth. I don't have a differential probe, but I can use the second channel with the Math function should I need to do that, for example in setting up the Phase Inverter. In reality, that is rarely done in amp repairs. However, I will do it in an upcoming amp build once I get through my embarrassing backlog of repairs.
Chris - looking at the big filament resistors off the tag board - was this perhaps a way of getting a 'pseudo' center-tap happening ? (when no center-tap is available from the transformer for the 6.3V supply?). (Helps noise/hum & is not intended as a way of 'taming' the filament voltage per-se). I don't have a the circuit to check for sure. ( but I do have a Mesa 22+) - so am very aware of the love-hate relationships amongst repair folk.
Hi Ian. Sadly I don't have time to go through the video again. By the time I finish recording and editing I am over ME, but if you have a timestamp for me I will be happy to look. I did however, look at the schematic before replying to you. Yes, the 2 x 100 R resistors are indeed acting as a ground reference. I assume from your msg that I had a brain-to-mouth failure.
So you prefer that the fuse be hot all the time, no matter what the switch position is? Seems like changing a fuse becomes a delicate operation. Maybe I am misunderstanding?
It is a very important and good question, Brian. What would you say to St Peter at the pearly gates when he shakes his head and asks, ‘Why would you have trusted your life to a cheap mechanical switch?” St Peter knows that if a short occurs downstream of the fuse (including the switch), the fuse disconnects the Active from entering any further into the amp. So by positioning the fuse before the switch, the entire circuit-including the switch…and YOU, are protected. Another precaution is to have the hot Active wire from the power cable connect to the REAR of the fuse holder. But you have made a valid point. I will make up a bunch of sticky labels to say: “To avoid death, remove power cable before changing fuse” Thank you Brian.
While I enjoy the sound of Mesa Amps, I've never been able to play though one without feeling there was something lacking. Perhaps I just don't know how to dial them in. They just don't gel with me for some reason. They obviously work for a lot of people. Guess I'm just not one of them.
I feel the same, Michael. If we use my caveat that all Mesas are unnecessarily complex, different for the sake of different (not better), they were NOT designed for ease of service, many are factory biased too cold, and suffer from pointless crossover distortion, then there are a few Mesas that I really like the sound of: The Mk I, Son Of Boogie (built by a drunk blind person) and the Studio 22 (without Graphic, same drunk builder).
What's up with the two non-stock mini switches on the front panel?...,btw,I met Randall Smith in 1980 and he claimed to invent tidal pools and the spatula
You are so funny, Ricky. Yes, I have seen some of Randall's other great inventions that stand beside the spatula. Like a negative voltage on the Phase Inverter (yes, restrain from commenting, oh ye UA-cam Trolls. I know it makes the tail resistor act more like a current sink.) which then is linked to the bias supply. I wish he had stuck to kitchen utensils. 😂
Sorry. I forgot to answer the first part of your question. Those 2 controls are normally Pull-Switch activated. Those pots were replaced at some time in the past and switches used instead. Not standard. I certainly would not have done it to this amp, but I must admit that it makes for a more reliable operation that is easier to see than a pull switch. The installation was done neatly.
@@theguitaramptech gotcha, thanks...I got a Mk ll in 1980 and then used them and MK lll's throughout the 80's...sounded great through old Marshall 4x12's...to me,they lost it with the Mk lV...tone suffered while it tried to be too many things at once...very gimmicky...now,out of mercy for my amp tech,I wouldn't consider one of their amps 😂
Some Mesa amps can sound very good. Others sound fizzy bad and are biased ridiculously cold to honour their commitment of "our amps don't need to be biased". To my taste, they are way overpriced for what you get, and unnecessarily complex. I can get a much better sound from my 1963 Brownface Concert.
I wish I had more respect for Messy Booga's than I do. The early ones could sound very good indeed, but still with shocking construction. As they got more complicated, the sound quality plummeted. To me they sound thin and buzzy. My apologies if you own one.
It is amasballs how you put this piece of crap(my opinion ) to lets say in decent working order, I knew Mesas where overpriced bullshit and this I have said I had not much of a. clue about Valve Amps many moons ago . This repair proofs me right and above all, this is the worst sounding amp you ever had on your desk, Carlos switched to Framus Amps AC 30 type, where he is now , don't know but it is obvious why. All the best to your Daughter and you.
I love your "no holds barred" description of Mesa Boogies. There is NO Tech I know that likes working on a Boogie. By comparison, every Tech hopes to work on a vintage Fender. Leo 100% knew what he was doing. I liked the sound of this Boogie once it was finished, but I hope it will be my last. Thank you for your good wishes for my daughter. It is her operation in 2 days time. Where are you from? I would like to tell my daughter.
Aha! I thought it sounded German, but my German is mainly learned from "Inspector Rex" (Austrian TV show from the 90s), so they are mainly dog instructions!! My German started to improve when I did a few jobs near Frankfurt, but everyone spoke English.
You are one of my favorite amp techs and always teach me so much. I really appreciate all of your work. I can only hope that I find a local mentor like you someday, you're a bit far from Chicago.
Thank you so much, VTA. I really appreciate your comments. Who knows...I may get to Chicago again, one day.
Dear Chris,
It's great that you brought this beast back on stage. Every guitarist is lucky to have you as a tech.
I just read in one of your posts that your daughter is very weak at the moment and the operation is imminent. I am thinking of you and praying for your daughter.
I myself lost my father to this terrible disease last week and know what you are going through.
Best wishes from Germany
Markus🙏♥🕯
Guten Morgen, mein Freund from Köln. You are very kind.
I am so sad about you losing your father. My father also went from pancreatic cancer. What a horrible disease this is. The surgeon and oncologist are expecting a full recovery for my daughter, but the journey is so hard. So much pain.
Many thanks for these two videos on the Mesa Boogie Mk1.
I discovered them at just the right time as I had my first boogie on the bench, having not had one for repair or service before . Your two videos helped me a great deal. I agree with all the points you highlighted. What a contrast with Fender who are unafraid to share their schematics and even PCB layout and test point values.
Once again thanks
Thank you, Stephen. I have made a commitment to myself (and those who care for my physical and mental health!) that I will not accept any more Mesa amps to work on. They are just not worth the angst. I feel sorry for those customers who fell for their hype, but its not my journey.
Dang, that was a mess sorted. Well done.
I don't recall if I showed the plague of dry joints. They were doing my head in. In the end the only way was to suck out all of previous Techs solder and replace it with quality solder.
hi Chris great information on cross over distortion.
Thank you. Yes, not many people fully understand crossover distortion.
Absolutely brilliant!
thank you Lars!
I would never usually watch any kind of a Boogie repair video, but I like your patient, thorough and electrical safety minded style Chris. Great job on that thing, I'm sure it's the best it sounded in many years, if not ever. I like simple, effective tools, so I'd definitely be interested in your capacitor leakage tester specs, btw. I Usually just lift the end opposite the plates and make sure its completely void of any DC whatsoever. I expected more crossover distortion too, than appeared on your scope, interesting. Randall supposedly purposely adds mistakes in some of his schematics btw, I'm told, so beware in the future. Best of luck with your daughter too.
That's the way I used to measure leakage, too, but the input impedance of a good DMM is so high that it poses no load on the grid side of the coupling cap to highlight any leakage. I'd be interested to see if the DMMs with a Low Z setting may sniff out the leaky caps. If you have such a meter, please let me know if it works. I will build a LED Leakage Tester Mark 2 when I can see daylight again. The situation with my daughter is of course a priority. Thankfully my customers are understanding and patient. If Mark 2 works well, I'll post a video on it.
Another magnificent video Chris..! I always learn so much from what I call a treat..! Great info and explanations of the AB type of amps etc..You're a star man.! Hope your family is doing well mate..Ed..uk..😁
Thanks Ed! Its always good to see your comments at the start of my day.
My daughter has now had the double mastectomy. She'll be leaving hospital tomorrow and then we hold our breath for the biopsy result. Thanks for asking!
@@theguitaramptech Good to hear Chris, wishing her all the best, with prayers .👍
Hello from Chicago!
G'day Dennis! Great to hear from you.
fab Mesa goodness
Hahahaha! Time to get off the whacky tobacky, Ian!
@@theguitaramptech better I stay on it with this crazy electronics I have to fix
@@moodyga40 maybe I should try it next time (hopefully never) that I need to work on a Mesa. In fact, a rollie of Petaluma weed may help get inside the mind of Mr Smith.
another great video
Thank you, FMF!
Really enjoy your videos. You have a way of explaining things that is filling in some of the gaps in my vary limited tube amp knowledge. I''d enjoy a video going over the reasons behind "hot" cathode biasing power tubes like in the VOX and in my Friedman Little Sister. Your thoughts on using a Variac and selecting tubes by spec to possibly increase tube life or just find the sweet spot tonally.
Thank you, Kent. I appreciate your kind words. The main reason why a variac is not the ideal solution for cooling down an amp, is that it will also have an effect on your filament voltage. Too high or too low a filament voltage may shorten tube life. A good rule of thumb is +/- 10% Max variation.
Hi Chris .........I enjoy your expertise combined with wit and wisdom. I have a Mark 1 RI sitting in the bedroom / music room of my home out here in the sticks of the deep south. I have wanted one for decades and finally have a real beauty with the wicker / cane speaker "cloth". It's the 100 / 60. I thought the reverb was rather weak so I replaced the 12 T7 tube with a new one which helped . Even with the reverb up all the way, it's just "ok".......nothing like a "surf" Fender reverb, which I didn't really expect it to be.......however, is there anything I can have done that might improve it ?
Thank you
Jim
Muscle Shoals, AL
Hi Jim. Wow. Muscle Shoals. Its on my bucket list. I just want to lean up against the wall outside the studio for a cool-dude photo and pretend I am someone I'm not.
Good question. As you know there are 4 parts to a Reverb circuit, the driver tube, the reverb transformer, the reverb tank and the recovery tube. Any one of those elements could be your issue. Fender uses both triodes of a 12AT7 to drive the reverb transformer, whereas the Mesa uses one triode. I would not expect your sound to hit the reverb tank as hard. Good luck.
@@theguitaramptech Thanks.....do you it might make a difference by putting in a 12AX7 instead of the 12AT7?
BTW........it's pretty neat to take the tour of FAME studios and listen to some master tapes going through their studio monitors. Being from the north, I have a hard time during the summer months here, but I do enjoy the music history.
Hello.. great and informative video series… Just wondering if you used a regular passive probe to scope the output..? And whether you scoped the single at the speaker terminals or power tube output..? possibly a differential probe..?
Yes, I use a passive probe, usually in the 10X position for less loading and improved bandwidth. I don't have a differential probe, but I can use the second channel with the Math function should I need to do that, for example in setting up the Phase Inverter. In reality, that is rarely done in amp repairs. However, I will do it in an upcoming amp build once I get through my embarrassing backlog of repairs.
Chris - looking at the big filament resistors off the tag board - was this perhaps a way of getting a 'pseudo' center-tap happening ? (when no center-tap is available from the transformer for the 6.3V supply?). (Helps noise/hum & is not intended as a way of 'taming' the filament voltage per-se). I don't have a the circuit to check for sure. ( but I do have a Mesa 22+) - so am very aware of the love-hate relationships amongst repair folk.
Hi Ian. Sadly I don't have time to go through the video again. By the time I finish recording and editing I am over ME, but if you have a timestamp for me I will be happy to look. I did however, look at the schematic before replying to you. Yes, the 2 x 100 R resistors are indeed acting as a ground reference. I assume from your msg that I had a brain-to-mouth failure.
Thanks
Thank you for watching my videos. I am so happy that you enjoy them.
So you prefer that the fuse be hot all the time, no matter what the switch position is? Seems like changing a fuse becomes a delicate operation. Maybe I am misunderstanding?
It is a very important and good question, Brian. What would you say to St Peter at the pearly gates when he shakes his head and asks, ‘Why would you have trusted your life to a cheap mechanical switch?”
St Peter knows that if a short occurs downstream of the fuse (including the switch), the fuse disconnects the Active from entering any further into the amp. So by positioning the fuse before the switch, the entire circuit-including the switch…and YOU, are protected.
Another precaution is to have the hot Active wire from the power cable connect to the REAR of the fuse holder.
But you have made a valid point. I will make up a bunch of sticky labels to say: “To avoid death, remove power cable before changing fuse”
Thank you Brian.
@@theguitaramptech That does make perfect sense. I went back and looked at how I did my Princeton, lo and behold, just as you say!
@@briansilcox5720 my man!!
While I enjoy the sound of Mesa Amps, I've never been able to play though one without feeling there was something lacking. Perhaps I just don't know how to dial them in. They just don't gel with me for some reason. They obviously work for a lot of people. Guess I'm just not one of them.
I feel the same, Michael. If we use my caveat that all Mesas are unnecessarily complex, different for the sake of different (not better), they were NOT designed for ease of service, many are factory biased too cold, and suffer from pointless crossover distortion, then there are a few Mesas that I really like the sound of: The Mk I, Son Of Boogie (built by a drunk blind person) and the Studio 22 (without Graphic, same drunk builder).
As a red blooded Mmmerican I feel I must tell you, the black wire is not active. It is hot!
HAHAHAHA! I'll take your word for it, Buck. I'm certainly not going to hold an ACTIVE wire to check if it HOT!
What's up with the two non-stock mini switches on the front panel?...,btw,I met Randall Smith in 1980 and he claimed to invent tidal pools and the spatula
You are so funny, Ricky. Yes, I have seen some of Randall's other great inventions that stand beside the spatula. Like a negative voltage on the Phase Inverter (yes, restrain from commenting, oh ye UA-cam Trolls. I know it makes the tail resistor act more like a current sink.) which then is linked to the bias supply. I wish he had stuck to kitchen utensils. 😂
@@theguitaramptech 😂😂😂😂
Sorry. I forgot to answer the first part of your question. Those 2 controls are normally Pull-Switch activated. Those pots were replaced at some time in the past and switches used instead. Not standard. I certainly would not have done it to this amp, but I must admit that it makes for a more reliable operation that is easier to see than a pull switch. The installation was done neatly.
@@theguitaramptech gotcha, thanks...I got a Mk ll in 1980 and then used them and MK lll's throughout the 80's...sounded great through old Marshall 4x12's...to me,they lost it with the Mk lV...tone suffered while it tried to be too many things at once...very gimmicky...now,out of mercy for my amp tech,I wouldn't consider one of their amps 😂
@@rickya3877 on behalf of your amp tech, I say Thank You!
I learned I don’t need a Mesa Boogie Mark 1
Some Mesa amps can sound very good. Others sound fizzy bad and are biased ridiculously cold to honour their commitment of "our amps don't need to be biased". To my taste, they are way overpriced for what you get, and unnecessarily complex. I can get a much better sound from my 1963 Brownface Concert.
Messy Boogie?
I wish I had more respect for Messy Booga's than I do. The early ones could sound very good indeed, but still with shocking construction. As they got more complicated, the sound quality plummeted. To me they sound thin and buzzy. My apologies if you own one.
It is amasballs how you put this piece of crap(my opinion ) to lets say in decent working order, I knew Mesas where overpriced bullshit and this I have said I had not much of a. clue about Valve Amps many moons ago . This repair proofs me right and above all, this is the worst sounding amp you ever had on your desk, Carlos switched to Framus Amps AC 30 type, where he is now , don't know but it is obvious why.
All the best to your Daughter and you.
I love your "no holds barred" description of Mesa Boogies. There is NO Tech I know that likes working on a Boogie. By comparison, every Tech hopes to work on a vintage Fender. Leo 100% knew what he was doing. I liked the sound of this Boogie once it was finished, but I hope it will be my last.
Thank you for your good wishes for my daughter. It is her operation in 2 days time. Where are you from? I would like to tell my daughter.
@@theguitaramptech When I see his nickname, he can only come from Germany :-)
power to the farmer 😂
Aha! I thought it sounded German, but my German is mainly learned from "Inspector Rex" (Austrian TV show from the 90s), so they are mainly dog instructions!! My German started to improve when I did a few jobs near Frankfurt, but everyone spoke English.
@@theguitaramptech I am from Germany . Have a good day
@@markusf.3441 You are spot on.