Hey, man. This was a real nice video. Working on amps is pretty insane. Some nice soulful playing, too. Music is life.
This video is just what I needed, on a slow night, great tone shaping and modifications ,Brad !
Awesome repair! Loved hearing the resistor box value changes.
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.
Nice repair/mods. Sounded great!👍😎🎸🎶
Another awesome video Brad, keep them coming.
Another fine fix! Great work sir.
The only Channel I don't fast forward thought the sponsor portion of the video.
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...
That was some PERTY playin! nice to hear a different style for a change....That amp sounds amazing actually, nice, full and buttery smooth!
Sounds great man! Great job!
Got that little amp crankin' and sounding good, Brad!
Thank you Mr. Guitologist for another great vid. No thanks for getting your SLTS solo stuck in my head, again. Cheers!
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
excellent job u did on this one brad sounds amazing,love this amp.lotsa mojo
Great repair video!
It’s nice how they isolated the chassis........ proceed’s to shake the bejesus out of it.
Classic.
Love the new vibes, too!
Dangit, Brad! Every time I watch one of your vids, I see another piece of test gear I need!
Great video Brother! You made something cool out of that tired old thing.
Hey Brad , love your Guitologist repair uniform ... Lol ... Good vid ... I shall do another shot now ...
Great repair
Very nice work..!
Nailed it.. Great job Brad!
Great playing
Got it sounding great in the end bro. ATB
Well done Brad you saved another one.
At Last !!!! Bet you'll be glad to see the back of this one (along with the Mesa).Patience is a virtue.
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.
Awesome job on that amp man
She sounds good. thanks for posting
Killer video!
The robot in that amp is howling "Oww Owwww Oww Oww" when you are plucking that D string
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.
Nice one Brad, Cheers.
32:19 I have a pair of Celestion G12s in a DIY cab, nice speakers IMO
Great sound
background music just right. thanks enjoyed.
The Toecutter knows you were playing guitar using your pinky Haha🤘🏼🤘🏼
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.
Fine video, Brad. You done good, kid.
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.....
sounds great love Celestion very nice
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.
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)
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 😂
The marshall lead 8412 Straight cabinet were loaded with the Celestion G12L 35w Speakers. They are not bad.
Flex!
sounds much better now.
Good video and playing...
Excellent!!!
First thing I said when I heard that motor boating sound was "bad filter cap". You ended up replacing them at the end. ;)
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.
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!!!
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.
One hell of a VCO!
I don't think you give your pinky enough credit when you play great job thanks
do input jacks all have resistors on them? also woul a jack to speaker have some sort of resistor on the speaker input?
Great Vid Thxs
Next Ampeg you fix should be a portaFLEX!
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!!!!
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.
Brad's a fine picker
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...
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.
Marshall used the G12L-35 mainly in their older Valvestate 4x12 cabinets.
Thanks Brad. These damned repair videos suck me in every time.
Great Shirt :) FLEX spaghetti westerns !
Nice Ampeg save Brad ... with older amps you just never can tell if it's going to be a Rogue One 😆
Now you have a Fenpeg.
In troubleshooting that ampeg you said r4 might be shorted. Resistors never ever short as they dissapate heat the resistance (from handlng to much current)as goes toward infinity (open). Love watching your videos. Not trying to judge, just paying attention. You rock
Yeah, watching back, I misspoke there. Probably I meant to say "open". Or I thought I was talking about the cap. You knew what I meant. ;)
How does everyone get the ddario NYXL stickers? I buy the strings but never find the sticker?
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?
Ill bet you get the whole "Cut your Coke Nails" all the time. lol
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
Cut a notch in the sucker nozzle for the iron tip - you'll get better suction.
That oscillation makes it sound like Doc Brown's amp from BTTF.
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 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.
Nice pickin man!
is that oscilation or modulation between hum and mororboating (oscilation)?
Recently got my hands on a 1970's Kay 50w sound fashion amp. Anyone know anything about this amp? I can't get any info on it. It has a plate on the back that says solid state but takes around 10 seconds to power down when it's switched off.
...nice playing ...ive always liked Ampeg products...."
That’s sounds cool like Lou reeds metal machine album. Lol
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?
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
That Ampeg has onboard effects!!! It's an oscillating 1/2 a pitch shifter with mild overdrive, too bad it's probably too late to return for a full refund.
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.
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.
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..)?
That amp has gone all EDM/Electro New Wave...
Great video, Brad! The amp sounds great, though the better part of it is your vituosity. Keep triggering us ol' timers by making repairs sans o'scope...
Last tune you played? Get it on? Awesome video as always
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.
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 UA-cam video could be about that.
First thought, ground loop, or maybe needs aluminum shielding
Thanks Brad. Nice work. After you got through playing then, could you fry bacon on it?
Surprises me still that in 72' they were using those circuit boards in there. Would have pegged that one for a class A only.
Sounds sweet now Brad!! This video shines a light on two of the main problems today... Patience & Perseverance.