I don't know why, but i watch a lot of amp repair videos. They hold my attention well, especially if it is a classic amp. This channel, plus Uncle Doug and one called Psonic Audio. I will do pickup swaps, but I am still not game to get inside my amps in a big way. I do not trust my shaky hands and 52 year old eyes that need replacing. The other thing is getting the parts is a pain in the butt in NZ. Everything has to be imported pretty much.
@@tfrost33elkhunterI am 57 years old now. After shorting the tube pin three to the nearby pin a half year ago ( it has happened way to many times) with my volt meter's probe, I have begun to wear reading glasses! A must!! And also use a clip insulated on the plate's pin three...no more free hand plate volt checking, or current checking! And I am making me a bias probe. Do it smarter and safer!! A shaky hand is bad news, so use alligator clip leads that are insulated. ✌️
@@HeadfirstAmps NO NO! The exterior condition, I enjoy your videos! I realize when components need to be changed , absolutely. I’m glad you you found the hum problem! I have a Laney AOR 100 that has that same hum, and like this Marshall, sometimes it came and went
Nice detective work, Jason! There are so many sources of hum, and its a pain to track it down. Its really impressive watching someone who knows their stuff figure these kinds of issues out.
This video is a life saver! Was getting 120hz hum and have a ppmiv in my plexi clone as well and sure enough both sides of the choke are measuring about 2ish volts AC. Would have never guessed!
Still working on the Gunslinger build (High Gain marshall-y circuit) and your videos are super helpful and informative, my wife always catches me watching these at all hours! Cheers from New England, USA. -Dave from Iron Age Amps
This was helpful. I have 100Hz hum in one of my new amps. And I was suspecting the choke to be: a) wired wrong, b) part defect. Becasuse no input, all at 0 and there was still huge hum. I will get back to this amp and check it today!
Its just a coil Jason. It either goes shorted or open. I'd say it shorted in your case, thus not providing the filtering effect but still allowing the current to pass. Nice troubleshooting tip!
Great troubleshooting! Did you put all four output tubes back in or just two as it arrived? Did you keep the PPIMV? just how cranked where your volumes on the recording? sounds great!! learned a lot again as usual Thank you again for another great lesson!!
Great result and playing mate. Just one minor corrective comment re your suspicion for the reason why the choke lost its inductance - highly unlikely due to some demagnetisation efect. Much more likely a shorted turn or few, possibly insulation of the enamel wire damage. Great use of AC voltmeter to probe for that kind of a fault, I usually use the CRO on ac coupling and x10 probe. Cheers from Sydney.
@@HeadfirstAmpsI'm curious, who do you use for rewinds there? We got one guy here (Alkay Transformers) who is semi retired where most repairers send the transformers (output and power) for rewinds.
@@HeadfirstAmps there is a very good and low tech way to check and measure inductance of iron corred inductors including power and output transformers documented by David of Elpaso Tube amps you may find of interest, here's a link to it if you haven't seen it. ua-cam.com/video/xbIvLTcoI8Y/v-deo.html Cheers.
These old early 70's Marshalls are supposed to be amongst some of the good ones, I think Angus Young from AC/DC has a few early 70's Marshall Super Leads in his collection, think he also has some Marshall JTM45s as well.
I tried my best to keep up, dont understnd half of it but a very interesting run through of everything and now sounds amazing! With regard to ripple, what effect does that have on an amp if it were increased or decreased? Is it less noise floor or something along those lines?
On the power supply for the tubes, you want pure DC with no ripple. If there is excessive ripple (AC) on that DC supply then you will hear it as hum in the amp.
@@HeadfirstAmps ahhh gotcha! Main reason I ask is because on the line 6 helix they have a ripple control and I never knew what it was meant for, I guess some people must like to dial in some extra noise to match an old amp they had or something.
Hi Jason. Great channel! Believe it or not those PCB mount pots are original in the early first gen ST1 board amps! Ive seen the same makes consistently in amps of that era in the amps Ive been in. Not saying that there aren't plenty of amps out there with replaced pots but the ones in your customers amp look to be the same as what Ive encountered.
So I also have 1975 100w superbass (written germany on the top inspection signature check list) and mine also has these pots with the black center and pcb mount, also thought they were replaced in their life but now I believe maybe you right and this is how they came out the factory. This vid was really interesting as most my components are identical to this 1974 made 100w which I thought was little odd. If anyone wants pics of mine hit me up. Once again thanks for the vid Jason!
@@Jediroller Glad to be of help! Theyre not pretty to look at but theres absolutely nothing wrong with them. While the 25ks in the mid and presence controls seem to be the most common Ive seen alot of '74-'75 1987s that use these pots through out
@@johnlucus5468 the only problem is I don't want to take them out of circuit to check if they are 25k pots..I guess that's the only way to check. When I replace my mains transformer I might do it then at the same time.
@@Jediroller Well the good news is that most of the time they will be ink stamped on the side and you might be able to read it without doing anything but again Ive seen these pots in 1meg, 250k, and 5k as well so all Im saying is that its not a big deal if you're amp has them and to not assume that they're not stock to the amp.
Jason, I just love bringing these things back up to snuff! The components, like electrolytics now-a-days are FAR superior to the old ones and should ALL be replaced in my opinion. Likewise, all of the carbon comps which drift all over the place over time and I've measured off by 50, 75, 100, 200%!! :O No wonder these things dont sound consistent! I've never had a bad choke situation either, so this is a first! Wonder what the hell happened and as original Marshall choke?!? One thing to point out is while working on old amps...old Marshalls, Blackface Fenders, old Laney's....I've had issues with amps on the bench and scratching my head as to what the fuck was wrong. In the end, in more than one case, it was actually the DIODES! So, I recommend replacing them also in old amps and just get ahead of the curve as without it and you fix whatever issue you have...recap electrolytics, etc....you're sitting on a timebomb and it's only a matter of time when the diode will take a shit! Anyway, had it on multiple amps and just relaying the issue(s) I've experience in the last 12 years in the business. When these things have all good components....goddamn it, they sound good and that classic tone! I seen this amp and the flat toggle switches and setup and said to myself....looks like an early 70s...yep!
@@HeadfirstAmps What do you think the diodes were for me?? LAST fucking thing!!! lol Now one of the first to get replaces besides the Electrolytics. Diodes have come a long way since the 60s and 70s. The one Blackface had 3 issues, so compound - I'd fix one and another pop up. The diodes were the last and 3rd issue...ugh. Yep, keep in mind.
Diodes should be easy to check though, right? A reading on one side, zip on the other. If they are bad you get leakage... is there another type of failure?
Pretty sure I used to own this amp about 8 years ago. I had it shipped from Chicago Music Exchange to Central Coast NSW and did a straight swap for a 82 2203 with a guy from Wollongong. Not sure what I was thinking but I was frustrated that I couldn’t get any overdrive out of it without going deaf. I use an attenuator with my 70 Superbass and 71 1987 these days and would love to have this old warhorse back. Edit : just watched the video and obviously not my old amp but jeez it looks like it.
Hey Jason,watching this got me wondering about an issue I am having…..I have my amp(Friedman) connected to a load box(Fractal X-Load),then the line out of the Load goes to a Marshall 9005 power amp,then to a cab….My issue is that when I turn the power amp all the way down,I can hear my guitar coming thru my studio monitors,and they are in no way connected…..the amp/load box is somehow “transmitting”my signal and it’s being picked up by my monitors(Yamaha HS8’s)…….It’s not loud,but it’s there…have you ever heard of this?…..I know it sounds crazy,but it’s happening…
P.S. You are saying the load box is not connected to your interface and DAW? Then that is weird. If so, then it would have to be getting to the monitors via the mains or something. Yeah, it must be haunted lol.
@@aquilarossa5191 correct….the amp/Load Box is NOT connected to my monitors in any way…….The amp is running at halfway up on the master volume,so without the load box,it would be deafening…..the line out of the load runs to my Marshall power amp then to a cab……If I turn the Marshall power amp all the way down,I can hear my guitar coming thru my studio monitors…Like a radio….it’s very strange,and I thought my ears were playing tricks on me…..My monitors and desk are on another wall,but my left monitor is 3 or 4 feet from the Amp/Load box….the other monitor is a good 8 feet away,and the ghost sound is coming out of both…..I don’t know…it’s strange..
I don't know why, but i watch a lot of amp repair videos. They hold my attention well, especially if it is a classic amp. This channel, plus Uncle Doug and one called Psonic Audio. I will do pickup swaps, but I am still not game to get inside my amps in a big way. I do not trust my shaky hands and 52 year old eyes that need replacing. The other thing is getting the parts is a pain in the butt in NZ. Everything has to be imported pretty much.
Same here! I built roughly 18 amps at this point and these guys are great resources! And for me it’s captivating content!
@@tfrost33elkhunterI am 57 years old now. After shorting the tube pin three to the nearby pin a half year ago ( it has happened way to many times) with my volt meter's probe, I have begun to wear reading glasses! A must!! And also use a clip insulated on the plate's pin three...no more free hand plate volt checking, or current checking! And I am making me a bias probe. Do it smarter and safer!! A shaky hand is bad news, so use alligator clip leads that are insulated. ✌️
I’d leave the exterior in that awesome used looking condition!!
Leave the old choke in there, and keep the hum?
@@HeadfirstAmps NO NO! The exterior condition, I enjoy your videos! I realize when components need to be changed , absolutely. I’m glad you you found the hum problem! I have a Laney AOR 100 that has that same hum, and like this Marshall, sometimes it came and went
@@HeadfirstAmps I edited my comment also, sorry about that
leave that look , its awesome, i'm surprised people dont actually pay for their amps to get "relic'd" like they do guitars !
Amazing. I never heard of a failed choke. They seem so robust compared to the other power supply components.
Very interesting, thanks for sharing your knowledge Jason. Love these Marshall repairs.
I always look forward to your Marshall Vids.
Nice detective work, Jason! There are so many sources of hum, and its a pain to track it down. Its really impressive watching someone who knows their stuff figure these kinds of issues out.
Thanks Wes, was a tricky one!
Jason, that was awesome! I hope you can continue to do these in the future...
Nice one. I did repair many of those then on the road. Hunting hum -> using a oscilloscope 😀
Wow, the playing at the end sounds so freakin good !
Thanks!
Jimi Hendrix is BACK!!! That sounds good!!!
This video is a life saver! Was getting 120hz hum and have a ppmiv in my plexi clone as well and sure enough both sides of the choke are measuring about 2ish volts AC. Would have never guessed!
It’s more common than I expected!
Still working on the Gunslinger build (High Gain marshall-y circuit) and your videos are super helpful and informative, my wife always catches me watching these at all hours! Cheers from New England, USA.
-Dave from Iron Age Amps
Hey Dave, glad you are enjoying the vids.
This was helpful. I have 100Hz hum in one of my new amps. And I was suspecting the choke to be: a) wired wrong, b) part defect. Becasuse no input, all at 0 and there was still huge hum.
I will get back to this amp and check it today!
Fantastic video Thanks for sharing Jason!!!
Yep, me too. Never worked on an amp in my life but I love these videos. Guitar setups too…lol
Can't thank you enough for the information you share
Glad it was helpful!
Man this thing sounds FANTASTIC... it's a beast!
Its just a coil Jason. It either goes shorted or open. I'd say it shorted in your case, thus not providing the filtering effect but still allowing the current to pass. Nice troubleshooting tip!
Im not a strat guy, but man, that looks an absoluty beauty…
GREAT INFO ....A MUST KNOW FOR ME AT LEAST...I LOVE MARSHALL! THE FOUNDATION OF NEARLY "EVERY BAND'S SOUND" THAT I LOVE 💪🧨🤯👌✌️
Very cool Info
I would love to see an episode on getting the hum out of an AC-30.
Great troubleshooting! Did you put all four output tubes back in or just two as it arrived? Did you keep the PPIMV? just how cranked where your volumes on the recording? sounds great!! learned a lot again as usual Thank you again for another great lesson!!
Par Excellence!
Great result and playing mate.
Just one minor corrective comment re your suspicion for the reason why the choke lost its inductance - highly unlikely due to some demagnetisation efect. Much more likely a shorted turn or few, possibly insulation of the enamel wire damage.
Great use of AC voltmeter to probe for that kind of a fault, I usually use the CRO on ac coupling and x10 probe.
Cheers from Sydney.
Cheers, I’m going to get the old choke rewound and will see what the go is once pulled apart.
@@HeadfirstAmpsI'm curious, who do you use for rewinds there? We got one guy here (Alkay Transformers) who is semi retired where most repairers send the transformers (output and power) for rewinds.
@@HeadfirstAmps there is a very good and low tech way to check and measure inductance of iron corred inductors including power and output transformers documented by David of Elpaso Tube amps you may find of interest, here's a link to it if you haven't seen it.
ua-cam.com/video/xbIvLTcoI8Y/v-deo.html
Cheers.
Sounds great with that strat. Old Aussie transformers are still cool. Ever work on old Australian/NZ gear?
I’ve worked on a couple of late ‘60s Strauss Lancers
That Marshall has a great patina 🙂it’s a shame that Luke turned the amp on and didn’t try to reform the capacitors first
Good Video. And good Strat soud. Kinman Pick-up's ?
That’s a Richie Kotzen signature with the stock Dimarzio pickups in it.
@@jasonktong1 Thank you
These old early 70's Marshalls are supposed to be amongst some of the good ones, I think Angus Young from AC/DC has a few early 70's Marshall Super Leads in his collection, think he also has some Marshall JTM45s as well.
I wished I had such a great tech. My amp still hums...
How did the tolex get so torn up lol
👍👍
I tried my best to keep up, dont understnd half of it but a very interesting run through of everything and now sounds amazing!
With regard to ripple, what effect does that have on an amp if it were increased or decreased? Is it less noise floor or something along those lines?
On the power supply for the tubes, you want pure DC with no ripple. If there is excessive ripple (AC) on that DC supply then you will hear it as hum in the amp.
@@HeadfirstAmps ahhh gotcha! Main reason I ask is because on the line 6 helix they have a ripple control and I never knew what it was meant for, I guess some people must like to dial in some extra noise to match an old amp they had or something.
Yes exactly. The AXE has a sag control which is also a power supply control.
Hi Jason. Great channel! Believe it or not those PCB mount pots are original in the early first gen ST1 board amps! Ive seen the same makes consistently in amps of that era in the amps Ive been in. Not saying that there aren't plenty of amps out there with replaced pots but the ones in your customers amp look to be the same as what Ive encountered.
Good info tnx John.
So I also have 1975 100w superbass (written germany on the top inspection signature check list) and mine also has these pots with the black center and pcb mount, also thought they were replaced in their life but now I believe maybe you right and this is how they came out the factory. This vid was really interesting as most my components are identical to this 1974 made 100w which I thought was little odd. If anyone wants pics of mine hit me up. Once again thanks for the vid Jason!
@@Jediroller Glad to be of help! Theyre not pretty to look at but theres absolutely nothing wrong with them. While the 25ks in the mid and presence controls seem to be the most common Ive seen alot of '74-'75 1987s that use these pots through out
@@johnlucus5468 the only problem is I don't want to take them out of circuit to check if they are 25k pots..I guess that's the only way to check. When I replace my mains transformer I might do it then at the same time.
@@Jediroller Well the good news is that most of the time they will be ink stamped on the side and you might be able to read it without doing anything but again Ive seen these pots in 1meg, 250k, and 5k as well so all Im saying is that its not a big deal if you're amp has them and to not assume that they're not stock to the amp.
Jason, I just love bringing these things back up to snuff! The components, like electrolytics now-a-days are FAR superior to the old ones and should ALL be replaced in my opinion.
Likewise, all of the carbon comps which drift all over the place over time and I've measured off by 50, 75, 100, 200%!! :O No wonder these things dont sound consistent!
I've never had a bad choke situation either, so this is a first! Wonder what the hell happened and as original Marshall choke?!?
One thing to point out is while working on old amps...old Marshalls, Blackface Fenders, old Laney's....I've had issues with amps on the bench and scratching my head as to what the fuck was wrong. In the end, in more than one case, it was actually the DIODES! So, I recommend replacing them also in old amps and just get ahead of the curve as without it and you fix whatever issue you have...recap electrolytics, etc....you're sitting on a timebomb and it's only a matter of time when the diode will take a shit! Anyway, had it on multiple amps and just relaying the issue(s) I've experience in the last 12 years in the business.
When these things have all good components....goddamn it, they sound good and that classic tone! I seen this amp and the flat toggle switches and setup and said to myself....looks like an early 70s...yep!
Shit, that's a good call replacing the diodes. Will keep that in mind. That Choke too f''ing ages to diagnose!! Was the last thing I suspected!
@@HeadfirstAmps What do you think the diodes were for me?? LAST fucking thing!!! lol Now one of the first to get replaces besides the Electrolytics. Diodes have come a long way since the 60s and 70s.
The one Blackface had 3 issues, so compound - I'd fix one and another pop up. The diodes were the last and 3rd issue...ugh.
Yep, keep in mind.
@@RozsaAmplificationLLC What were the symptoms of the bad diodes?
@@lowqualityguitarvideos noise and sounded like shit.
Diodes should be easy to check though, right? A reading on one side, zip on the other. If they are bad you get leakage... is there another type of failure?
Pretty sure I used to own this amp about 8 years ago. I had it shipped from Chicago Music Exchange to Central Coast NSW and did a straight swap for a 82 2203 with a guy from Wollongong. Not sure what I was thinking but I was frustrated that I couldn’t get any overdrive out of it without going deaf. I use an attenuator with my 70 Superbass and 71 1987 these days and would love to have this old warhorse back.
Edit : just watched the video and obviously not my old amp but jeez it looks like it.
Hello Jason.
Hi!
Hey Jason,watching this got me wondering about an issue I am having…..I have my amp(Friedman) connected to a load box(Fractal X-Load),then the line out of the Load goes to a Marshall 9005 power amp,then to a cab….My issue is that when I turn the power amp all the way down,I can hear my guitar coming thru my studio monitors,and they are in no way connected…..the amp/load box is somehow “transmitting”my signal and it’s being picked up by my monitors(Yamaha HS8’s)…….It’s not loud,but it’s there…have you ever heard of this?…..I know it sounds crazy,but it’s happening…
How close is are the monitors to the rest of the rig? Especially the amp and the load.
@@HeadfirstAmps The right monitor is about 3 feet away from the amp/load box….The left one about 7 feet or so……
Sounds like it haunted. Ghost notes coming thru those monitors. Creepy huh? Better call Ghostbusters. :D
P.S. You are saying the load box is not connected to your interface and DAW? Then that is weird. If so, then it would have to be getting to the monitors via the mains or something. Yeah, it must be haunted lol.
@@aquilarossa5191 correct….the amp/Load Box is NOT connected to my monitors in any way…….The amp is running at halfway up on the master volume,so without the load box,it would be deafening…..the line out of the load runs to my Marshall power amp then to a cab……If I turn the Marshall power amp all the way down,I can hear my guitar coming thru my studio monitors…Like a radio….it’s very strange,and I thought my ears were playing tricks on me…..My monitors and desk are on another wall,but my left monitor is 3 or 4 feet from the Amp/Load box….the other monitor is a good 8 feet away,and the ghost sound is coming out of both…..I don’t know…it’s strange..
I would have returned it to original. Including new electrolytic capacitors of course.
You’d have rewound the choke? I don’t have those skills.
@@HeadfirstAmps 😁
just wow lol
Puoi spiegarmi perché ha due valvole diverse e con due può suonare lo stesso