Amp Wars - The Ampeg Strikes Back
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- Опубликовано: 1 окт 2024
- Here's the second part of our Ampeg GU12 repair excursion.
PART 1: • What was Ampeg Thinkin...
PART 2: • Amp Wars - The Ampeg S...
PART 3: • He Heard a POP...Then ...
PART 4: • Has God Finally Forsak...
In this video we'll find out a sick 70s Ampeg can accidentally sound like a Jedi light saber. We'll also do some mods and stuff like that.
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These comments are cracking me up. You can always tell the newbies to your channel as they always bring up the exact same things. Maybe you need a disclaimer:
1. Brad has a scope but doesn't like using it as it makes for boring videos.
2. He picks with his fingers so has long nails on his right hand.
3. Yes he says Tremelo a little different than most.
You really do need to get a good oscilloscope. Your at the point in your technical skills where without one your going to be holding yourself back. I often use 2 or 3 at once when working on amplifiers so I can see induced ripple on power supply with signal modulation, and a current probe to monitor actual current VS voltage together at various points. A decent dual trace 100MHZ analog scope, or a 500MS DSO scope will be immensely useful. You may have seen the filter cap failure by looking at the rail before even applying signal. Your understanding of circuit function is growing...
Pretty soon he'll be a pofesonal.
around 5 mins he says about using his oscilloscope
With the price of a scope being what it is now especially for audio there's no excuse for not having one.
I just typed the exact same thing in another comment before seeing this one. He is ready for a scope. He is ready to step up to being an actual amp tech instead of a poker arounder. A scope is a step in the right direction. At least he is talking about one now. He could also vastly improve his knowledge by reading books like Tonnes of Tone and The Ultimate Tone series by Kevin O'connor. Dave Funk's Tube Amp Workbook. The Dan Torres book. Kendricks A Desktop Reference of Hip Vintage Guitar Amps is also good written education to apply. Those are all newer tube amp books.
Y’all understand that he already has one, right?
Flex!
My first real amp was a Gemini II that I "borrowed" from my guitar teacher. My previous amp was a little solid state number from Monty Wards - it died unexpectedly. I was told that the Gemini did not work, so I took it apart and my father noticed a resistor that was defective. We went to the tv repair store (1971) and bought the resistor, soldered it in and it sprung to life. That amp had great tone, but was just not loud enough - people were using Marshall stacks in clubs! So, Dad and I went to Washington Music Center (aka Chuck Levin's) and settled on an Acoustic 134 which was their version of a Super Reverb, sort of. That amp had no tone, but it was brutally loud. I remember playing gigs with that amp and doing things like unclipping speakers to try to get a more reasonable volume levels. Eventually, I modded that amp by wiring the output of channel one into the input of channel two. Great care had to be exercised when setting volume levels. Around 1976 or so, I exited the music business to go to college and the amp was sold along with my treasured 1972 SG Standard. As it happens, I had a friend that had a Twin and Les Paul Custom, but he could not play. So, he "loaned" them to me until one day years later he showed up at my parents house inquiring about his gear. I wanted to buy them, but had no money since I was still in school. Reluctantly, I loaded them into his car and that was that. I could have probably bought the combo for $500 which was a good deal. Oh well...
Yes, if you increase R12 the sound would get basier, because you change the frequency roll of of the filter it forms with c8 to a lower frequency. If r12 seems to be too low you may want to check c8 for leakage, as that would make the sound both less basy and weaker by reducing the resistance of the pair r12 and c8 (Not a guitar nut, just general electronics guy)
It still would have been nice to see what a clean sinewave looked like on the scope through the entire volume and tone setting range.
Sometimes you can create issues that are not all that obvious with only your ears as the test.
It also gives you a frame of reference when you start.
Great videos. Really appreciate the passion and effort you put into these excellent as well as entertaining sessions.
Keep up greasy work.
When you get hold of schematics like that, do you copy them or record them somehow for future use? Is there somewhere you might send them for folks to use in the future?
Sounds sweet now Brad!! This video shines a light on two of the main problems today... Patience & Perseverance.
The only Channel I don't fast forward thought the sponsor portion of the video.
Ok. Impressed. Subbed. Lol. Nothing like meeting critical thinkers of logic that also share love and passion for music arts and it's gear. Though I quit tearing shit apart years ago , it will be my pleasure learning these diode and chips with glorious soldering iron goodness. All with great adult criteria.. Much unlike the ones trying to pass off opinions and grammar school level music theory like Mr. return it. Lmao
Yeah, but take a look at the regulars here who are adamantly repeating that he needs an oscilloscope to service any electronics properly. Without a scope, you have no idea what is exactly happening. You cannot look at the actual signals or how a component is treating the signal. Of course with a scope his vids would be 10 minutes, because that is how long it would take to pinpoint the problem with proper test equipment. He recently tried to find the problem in a Mesa combo. He ended up taking apart the whole Mesa Boogie amp to parts bin pieces because he could not fix it after several attempts without a scope. Massive failure there. The amp went from playing on stage to being parts bin fodder because of power tube bias runaway that Bradley could never fix. I guarantee that he would have fixed it if he would have used an oscilloscope and 3 multimeters monitoring different voltages in the circuit. He would have been able to pinpoint the problem and correct it instead of gutting the amp he could not repair. Not impressive.
He has one Hugo.
HUGO FUGUSEV I'll admit that that video was painful for even me to watch. Maybe the moral of the story is not to even waste our time on those amps.
You're so wrong and you don't even know what you're talking about dude. That amp had a conductive board or some other issue that a scope would not have helped in anyway to isolate. If you think that, then please, by all means, give me detailed analysis of what I should have done to determine the problem given what I showed in the Mesa video. Maybe your very first RUclips video could be about that.
Dunno. There is nothing wrong with 2M2 + 51pF.
SLO100 and your favorite Mesa have 2M2 with some 80-470pF tone shaping part. Marshalls and Laney have 470k + 270-470pF etc...
As do Fenders (where the reverb amd dry signals are mixed) in fact it seems like they're doing exactly the same thing here. Attenuating the signal between stages is good for distorted tone (gain staging)
Fender Twin Reverb amps use a 3.3M or 4.7M resistor with a 10pf cap across it for tone shaping. A resistor with a small cap bypass is the STANDARD tone shaping used between stages in most high gain amps. Even Trainwreck amps used them. Still no scope to really look at what is happening and immediately pinpoint the problem in the circuit either. This is kid stuff, really. I like Bradley, but I think it is time he moves up to being a real amp tech instead of a poker arounder. Read more books, like the Torres book, The Dave Funk workshop book. London Power books like Tonnes of Tone and The Ultimate Tone 1 and 2 etc.
Yeah it is fine, the 3M3//51p is a part of a mixing stage.
You guys are missing the forest for the trees here. This amp is QUIET in stock form. Sure that grid stopper and cap network aren't unusual in a lot of amps, but this isn't those amps. There is just NO VOLUME in this amp design! It has exactly two gain stages in the preamp with a James style tone stack shoved in between them. Not exactly a Fender Twin, is it?
I have literally played 5W Fender Champs that were louder than this thing. They have to use .1 coupling caps just to eek out as much low end gain as they can through the amp and they still tried to keep it clean. The couple mods I did are easily reversible if some other tech thinks he's smarter than me and wants to put it back to stock. He'll very quickly find out I was right though. The changes I made made the amp louder. I appreciate the critical eye. But if you venture into dick measuring, I'm going to have to insist you get off your asses and post your own videos detailing the brilliant work you're doing with amplifiers, preferably the model in question.
Don't be so grumpy comrade. :)
Treble bleeding cap adds some crispiness and responsive-ness/active-ness. Dunno how to describe in English. :)
And there are lot of popular mods - to add a small cap to gain pot in amps & to guitar volume pots etc. It adds more gain and prevents farts from bass strings.
You tried different resistors without cap. So my point was - you play well on any type of old crap but owner might dislike tone change. %)
We already seen this amp. Who wants this Jedi to return in the next episode? %)
Regarding my brilliant work with amps I have to admit I'm lucky I build amps for pleasure as a hobby. Besides lot of pedals for last decade I built 3 SLOClones, couple of SE amps and number of tube preamps.
So from my limited experience I can tell this thing has not many gain stages and cathodyne phase inverter (with 1/2 of 12DW7 ). No wonder it's quiet and speaker is rated low.
You could try to replace 12DW7 with 12AX7. You are welcome %)
Brad it’s been said before but I’ll say it again - you are a fucking killer picker dude. You’d be great in a role as a lead player in a modern country band with a hard rock edge.
Thanks. That is nice of you to say.
I'm pretty sure that's the wrong style reverb tank for that mounting plane. This one is meant to be mounted horizontally, open side down.
Could be.
12:22 Damn, I wish you could get those speakers for 8-9 bucks these days. LOL
Mikey You sure can, as long as you’re satisfied with also getting a wage of 70 cents per hour, like they did at the time.
But seriously, $9 in 1957 is equivalent to $81 today. Which is pretty comparable to the modern cost of name brand speakers in. A new Eminence Cannabis Rex, for example, has an MSRP OF $89.99.
I know, that is pretty much a joke.
сгибать !! That's FLEX !! in Russian. DOH !
How do you read/pronounce that ?
^^i still want to know
The robot in that amp is howling "Oww Owwww Oww Oww" when you are plucking that D string
Us Ampeg guys are having kittens watching you mod the resistors in that GU12, it is worth a small fortune in its stock configuration. Ampeg has been using the Jensen C12-R with 7591's in push pull since the early sixties, while not the most efficient speaker they sound great and simply replacing it with something more efficient is enough to boost the 7591's volume significantly. without additional mods. You and UD have been an inspiration to me but please try to leave the vintage pieces as stock as possible. As far as chassis go I have a 64 reverberocket on my bench that is a little bigger than a carton of cigarettes and would love to have the acreage of the GU12 to work with. I have to admit your repair sounds great.
I disagree. This amp isn't worth a small fortune of the current market. Ampeg GU12 is not a highly collected or regarded amp, and for good reason. There are tons of design flaws, which I pointed out in the two videos I did on it. There are better Ampegs out there. This was obviously going after the lower end of the market at the time it came out. After cramming in the reverb and trem, there is barely enough gain to move the speaker cone. I guess that's why they figured they could get away with using a vastly underrated speaker.
That amp was a turd the day it was made. Someone who would pay anything significant for that hunk of crap just proves there is a sucker born every minute.
The 1976 AMPEG G110 FET (FIELD EFFECT TRANSISTOR) with Tremolo/Reverb is a studio workhorse. A must have. Get one you'll see. 😊 I'm a tube head, but one day on a walk right in my path on the sidewalk , like a gift from the heavens sat a super clean Ampeg G110 TREMOLO REVERB amp 'FREE TAKE ME'. Itook it home and it worked 100%! It was like, " Hey you, tube nut. What I gotta do, track you down?" lol
Thanks Brad. These damned repair videos suck me in every time.
i wish i could understand what you do.... i love this kinda stuff. i can mechanic my way around most things... but electronics seem like engineering and a lot of "thinking" thank you for sharing your gifts.....
32:19 I have a pair of Celestion G12s in a DIY cab, nice speakers IMO
Awesome repair! Loved hearing the resistor box value changes.
man, i had a reverberocket r212r reissue as a teen. my favorite amp i've ever owned. too bad one of my bandmates stole it and disappeared.
F
Next Ampeg you fix should be a portaFLEX!
Hey, man. This was a real nice video. Working on amps is pretty insane. Some nice soulful playing, too. Music is life.
Something doesn't sit right with me. I find it hard to believe that Ampeg designed an inherently unstable and oscillation prone circuit. I think rebuilding the power supply solved more than you thought it did or perhaps there are some leaky coupling caps contributing to that oscillation that is being masked by the changes in bias resistor values. I've gone down rabbit holes like that before, it's easy to do when you're that far into an amp.
I got the curio kicking loud and clear! Thanks for the motivation because I probably never would have fixed it without finding your channel. Go to my RUclips channel and check out the little riff I put together on it. Its not great quality but you will get a sense of the tone. Once again thanks bud. Love your channel. Keep keeping the old stuff kicking!!!!
Just found out a friend of mine is selling one of these. He junked the whole board and had a new one built re-valved it and it apparently sounds as "awesome" as yours. Sounds great.
Those ‘70s amps suck. The ‘60 Ampeg stuff was good. The B-15 was a great flip top amp. I bought a Reverborocket amp. It had a 12” Jensen. A guitar amp, I used it for a mic for vocals and a Farfisa Combo Compact organ. The Reverborocket new in about 1966 or 1967 was $125. The tremolo circuit had something interesting. When one of the controls was cranked to 10, continue crank, and it clicks into a hardened position. It gives an extreme pulsation.
Ya, I knew what you meant, not sure about anyone else. All said, I enjoy your videos. You get results and that's what matters.
I would have gone for DC leaking on that cap going to the trem control. Following the path on that schematic it goes through to ground through the tone controls. I thought it might be a combo of resistance/capacitance levels that started the oscillation.
C2 is open. Resistors provide DC bias. Capacitors give you AC gain, which was not present in the first stage. DC operating point looked good (122V on plate) which means both R4 and R5 are fine. If C2 is not there (open), then you have no AC gain (audio is AC, not DC). You replaced DC resistors while ignoring AC capacitors! I was shouting at my monitor.
Aloha Brad - Not certain of this is accurate, but audio dudes if yore advised me that speakers are more prone to be damaged by under power. Speaker rating exceeds the power an amp can provide.
The way it was explained to me is that speakers blow when insufficient power causes the magnetic field to collapse, causing the speaker to snap back with sufficient force to cause damage.
The logic is that an amplifier with greater headroom will allow the speaker to travel the full range smoothly and will never snap violently due to amp derating, over heat, basically driving an amp to death.
That may be why the original speaker has a lower power rating than the amplifier. If the original speaker is 15W and the amp is rated at 19W, there is 26% headroom to allow for amp derating at high temperature, or general degradation.
Love your vids, and shit posts!!!!
And for years I've thought I'm doing something wrong with a solder-sucker because I have to pump it so often - glad to see that a pro has to work the same way.. Nice work Brad.
Could it be this video is stuffed with ads (which I'm not used to on your vids..)?
Hey Brad, I see your channel is attracting a lot of experts. I see you as a guy that feels that an amp should perform a certain way. In truth, I think we are all that way. Those guys that were horrified by your repair tactics and claimed that you were hacking a classic amp are in a camp that I don't understand. Keeping something original for the sake of originality is crazy when the item can be made to perform better with some modification. Amps of all makes have been constantly modified at the request of the artists that use them to make a living. I believe your customer was planning to use this amp. I don't know if he is trying to make a living with it but, I do know he would do better with it after you got done with it than he would of without your work.
Great Shirt :) FLEX spaghetti westerns !
you should make a pedal to duplicate that oscillation,., like the guy that invented fuzz.;.;lol sounds like a old sifi movie .and tell the guy to buy a fender ... lol
Wow what a difference in volume with the 3.3k on R4. A few different parts in that design were bogus. But you got it sounding so much better and solved that. Nice Job :-) This is the 3rd Ampeg video ive watched in the last 24 hours on your channel. :-) I have very little experience with Ampeg tube amps.
What type of pickups are in that tele you used at the end ?
Is there a reason that you use a signal generator rather than something like a looper pedal playing a loop of actual guitar signal? I would think having a genuine guitar signal would make it easier to know how the modifications are affecting the tone of the amp.
10:30 Am I seeing things, or does that tone stack board have a bunch of cracked solder joints? The volume is the worst, but it looks like bass as well.
First thing I said when I heard that motor boating sound was "bad filter cap". You ended up replacing them at the end. ;)
How does everyone get the ddario NYXL stickers? I buy the strings but never find the sticker?
motorboating, look at power supply and biasing. Any signal, even hum draw ps down.
Dangit, Brad! Every time I watch one of your vids, I see another piece of test gear I need!
It’s nice how they isolated the chassis........ proceed’s to shake the bejesus out of it.
Classic.
Another great vid... thanx Brad. Better than movies fer me anyway.
Did you have any more thoughts as to the lack of cooling in this
oh so strange design?
Cheers
7591 run hot. The direct mounted 7591 are a bad design, clearly. No breathing holes is a bad design too. The chassis is made in sections though and there are some small gaps that help dissipate some heat, but it could have been better. Some louvered breathing holes in the top and bottom would have been nice.
Hey Brad , love your Guitologist repair uniform ... Lol ... Good vid ... I shall do another shot now ...
The end result sounds good, but I am confused as to why you modified the circuit in an attempt to get rid of the noise? I am fairly certain that Ampeg wouldn't have released an amp that had that noise so to draw a conclusion that their circuit design caused the noise and that modifying it was necessary doesn't make sense to me. I am not busting your balls, just trying to learn. Thanks Brad for your videos. I am learning a lot.
This is Part 2 of this repair. One of the main complaints is the amp is very quiet.
My bad. Didn't realize that was the same amp. Good work though. Sounds great
Seems every Ampeg has a problem steming from Jack plug grounding,
I want a pedal that sounds like 3:32. It should be called FlexFuzz.
Declusterfucked. Typically. Hard work reaps rewards. Bravo.
Nice Ampeg save Brad ... with older amps you just never can tell if it's going to be a Rogue One 😆
For the life of me, I don't get why guitar MUST always be so dirty. The guitar tone is lost due to the overdrive, even at the softest articulation.
How about loud AND clean, isn't that supposed to be an option?
If music is a language, this sounds like screaming at the listener, is that the only way to speak?
The problem with this amp is there aren't enough gain stages to efficiently boost the signal and make it loud enough while remaining clean. There's no cathode follower before the funky tone stack. They were clearly going for features over volume by using up 3 triodes in the pursuit of tremolo and reverb.
You know how to fix this Crap... Gas and Match. Torch it
is that oscilation or modulation between hum and mororboating (oscilation)?
Cut a notch in the sucker nozzle for the iron tip - you'll get better suction.
is it possible they neutered the first stage to avoid blowing the lower wattage speaker
dear mr guitarologist my amp i bought just over a year ago, my problem is i hate noisy amps. i understand about the 60 cycle hum, bad cables, dirty power sources, etc etc, but i have a gut feeling it may be something else, oh and the tubes i had replaced and biased, i believe it may be a bad ground or something simple, that's just an uneducated guess on my part, what can you suggest? taking to local tech? i don't think there are too many where i live thx
Bad grounding schemes are the #1 cause of hum outside bad preamp tubes.
Why does everything sound distorted, like there’s a fuzz tone on it?
I would think that it is for what you would call bed room musicians.
Sounds just like this amp: ruclips.net/video/R5paXeKX-W8/видео.html
Sounds like the nuke amp on back to the future.
About time 🙄😂 good content takes time I guess
That’s sounds cool like Lou reeds metal machine album. Lol
Hey Brad ... Don't know if you upgraded your Variac ... but there's a mod that can do to get the Variac to display right info, right at the time you turn it on......
I did mod it to zero later on.
You know, you can take those 6 nuts off on the under side of the chassis and that aluminum plate comes off to give you access to all the components on the board. That's why that plate is there, to give you easy access to the components.
There is a Part 1 to this video linked in the description. I go into that in that video.
3:24 It is the early version of Alexa, whoi, whoi, whoi! Want's to tell you, she's hurt when you pick the strings too hard, LOL!
I can only imagine what the repair cost!
Pajamologist 🤘
Jammy work day!
What happened to shit post friday?I like that show did i miss it?
Ill bet you get the whole "Cut your Coke Nails" all the time. lol
I love my Ampeg! But I'm (mostly) a bass player
Im at 20: 19 into this Im guessing that c17 isnt about bright it is to stop oscillation and its the problem. lets see what happens.
as I suspected. when the resistor R23 starts to wane ,.oscillation will return. Especially since you took the resistor value even closer down to Oscillation. But what do i know.
I have an Ampeg BA-115, it too is terribly soft and a Marshall MG100DFX plays much louder than it can. I need help with is because it overheated. I have the schematics of it but I can not read schematics. I want to replace the Caps which are 4700 UF 50v 85 Degrees celcuis and MOSFET IRPF9140 and IRPF140, but I cant find these parts at all. I am from South Africa, so I cant even send the AMP in to you.
Hey Brad, question: You're an amp guy so who better to ask? A while back I had bought a Marshall MG250DFX (the older model with an actual power switch, not the new one with the big round button). Anyway, the chassis stopped working one day and I'm not versed enough in amps to repair them. So I took the chassis out, converted the rest of the combo as a 212 cab and use a Marshall head with it now. my question is, I'm selling the old chassis for parts or repair. What price would you put on something like that?
Nice repair/mods. Sounded great!👍😎🎸🎶
Ampegs new ring modulator fx.
Well done Brad you saved another one.
Another awesome video Brad, keep them coming.
Sounds like a cap issue causing motor-boating/ oscillating . I've had filter caps induce this kind of tones with weird harmonics like that. Still watching so we'll wait and see. Update : Yeah, I’ve heard that before in my times under an amp hood. Filter caps will induce those weird oscillating tones and strange harmonic overtones. I always put the amp on the scope as soon as it hits the bench if it powers up. It will tell you a lot in a hurry. You need a good tone generator, load resistor and use the scope. Will save you a lot of time and aggravation and you won’t have listen to the tone ring your brain for an hour 🤪 I have and old analog 25mhz scope for general probing and the 4 channel Rigol 1054Z digital scope for checking a lot of things on the output, RMS, frequency at the output to see if its matching what’s going in and most importantly the waveform. I like to see the clip point, crossover distortion points ,and ripple and oscillating . Things that aren’t always audible.
Speaking of speakers....I salvaged an old Kalamazoo "Bass" amp from a friend, the cab was destroyed, I pulled the chassis and controls in hopes of re-installing them into a custom head cab.. ( hasnt happened yet, since I need to find help figuring a few things out..) but since the speakers were sealed in a closed cabinet, before throwing the destroyed cabinet out, I cracked the sucker open, and found a pristine pair of Jensen C10P speakers. They are now installed in a custom wood cab I made myself, but strangely enough, I contacted Jensen to find out for sure the power rating of these speakers, and Jensen told me, they dont have specs on those speakers, dating 1966. I was flabbergasted, that a company as old as Jensen, wouldnt be able to trace these back. The woman on the phone told me that back in the sixty's, they sold speakers to third party vendors for their applications, so they may not have a record of the versions sold to Kalamazoo ( Gibson). I've found a few things on the internet about these speakers, but nothing concrete. I figured, since Kalamazoo made three versions of the "Bass" amp, ( one labeled "Bass 50", another labeled "Bass 30", and one labeled just "Bass"....mine is a "Bass" ) that from the power tube configuration, it was probably a 30W'r. So the speakers may be 15-20w ceramic speakers? Maybe...I have them in a stained dove tail pine cab, and use them with a few low wattage amps I have...kinda weird huh? If you ever get time, That old Kalamazoo could really use a pro's help.....( hint, hint)
hey brad been watching your channel for a while mostly from my phone think I messaged you once about building an amp for me from a amp I was going to buy on ebay but my phone went down and now I have a pos phone that never notifies me for emails anyway I have this old school pioneer sx 1080 that Ive had for a really long time well anyway bout 7 yrs ago my son plugged a aux cord into the phono jacks in the back to listen to music from his phone well it overloaded the left side circuit and now the left side is super low volume was wondering if you ever work on those kind of things at all the stereo is worth 1000 or more when in perfect working condition I have been into vintage electronics for most my life and have a collection of old gear like that and this was my favorite silver faced amp from the era just a question I thought I would pop your way I know you mostly work on guitar amps and tube stuff so just a question
lol. just hearing the hum makes me nervous.
Do the owner a favour and PtP that SOAB!
Just another successful spankin sounding mod by the Mighty Brad😎.
I understand the comments about keeping the amp "stock", but I'd rather it Rock. As usual you have made a great performing/sounding amp. Rock on Brad!!!
Throw a EV SRO in there? 😂
That's what I did to anything I ever owned....until!
I like your thinking on t/s ing .
The lounge music was killin me tho! Good DAY.
I got the same hand, just never really thought much about it ,until You brought it up!! Hell I'm 60+ and never really thought about J Hendrix or other " alien " players hands.
Learn sumtin new evrday!
Sounds like it should!
That was a learning experience. You should specialize in those amps now you know the circuit from beginning to end. School of hard knocks learning
Just put a fuzz pedal in front of that amp, then with the tremolo and reverb (sorry, I meant "dimension") I'm in guitar heaven!
I had a strange idea...... Make a Master Catalogue of all strange amp sounds, record them for future use {audio fx } . Look online and see how some sound fx were made by random sounds (some are simple some are just plane Bizzar.
Ampeg GU-12, That was my first amp when I was 13! My LP Black Beauty into this kicked ass. Mine was pretty bullet-proof. Love to find another one of these.
Are you wearing those trousers for a bet?
Keep Rocking in it, not of it !
russions don't need no O scope FLEX!
sounds much better now.
love your show but I'm buying you some finger nail clippees... it might be a job hazard , not sure?? would hate to see you involved in some kind of wookie thumbnail accident...
Now you have a Fenpeg.
Dude, you wrecked that amp. You really should have debugged the actual problem (oscillation) before assuming that Ampeg didn't know how to design an amp and second guessing all of the component values in the schematic.
No, I didn't wreck the amp. Everything I did is reversible. I'm not assuming anything. This is a poorly designed amp from the standpoint of maximum volume. They went for an approach of cramming in reverb and tremolo, leaving only two stages of actual preamp gain to boost signal before the PI and output. Then there's that James tone circuit stuck in there after the first stage. If I really wanted to "wreck" the amp, I'd yank out that atrocious board and build something in it that would move more air and still have the same features.
Another fine fix! Great work sir.
Phillip McKnight says that he's a better guitar tech, than you are an amp tech... reaction?
Funny, when you are soldering a component in place a puff of solder smoke comes at the direction of my face. Out of habit, I hold my breath 😂