Diagnosing a dead guitar amp using signal tracing and signal injection. This technique helped to narrow the problem to a very specific area of the circuit.
Thank you so much for this video!!!! My Trace Elliot recently went down and most repair shops are tube snobs where I live in England so, VERY unhelpful! This made perfect sense to me thanks to you explaining it so clearly. Opened mine up, went through, found the issues....same problem! Cheap/shoddy jacks that had oxidised! Problems solved. THANK YOU SO MUCH!!!!!
I have just figured out why there are no skilled amp technicians or micro electronic hardware engineers making these videos, simply if they broadcast all the fixes for mediocre problems, they will be doing themselves out of at least $100 bucks, at least an hour,. It is frustrating, greatest respect to you sir, i simply wouldnt bother a little knowledge can be a dangerous factor. an exsasperated soundless solid state amp guy.
This was a really great video! I hope you are still making these! I'll try to find more after this post. I always enjoy watching someone's diagnostic approach to diagnose and repair circuitry; especially when they explain what it is that they are looking for, and what they expect to find at each point along the way. This demonstrates that you have a thorough understanding of the signal path. In my mind, this is the very best way to make any kind of tutorial. If all of your videos take this approach to diagnosis and repair, anyone with the interest in learning about audio amplification diagnostics would benefit greatly by watching your videos! This is the first video of yours that I have seen, and look forward to watching some more! Currently, I am diagnosing failure(s) in a Pioneer SX-1080 stereo receiver, and suspect parasitic oscillation as the primary cause of failure. I found this video while searching for some mixed frequency content injection techniques, as I am going to try to reproduce the oscillation (the oscillation is not present at idle, nor with a fixed frequency test signal (20-20Khz), incremental). Just my two cents : Anytime you can make a repair without the soldering iron is welcome! I will take those kinds of jobs anytime. That's always sweet. I have always preferred to remove the PCB; I have never used a mirror. But I must confess, a mirror could save a lot of time if it will fit! As far as the corrosion in the jack(s) is concerned (outside of ingress of a compound into the jack itself), the most likely cause of corrosion would be the metallurgical differences between the 1/4" male plug that goes into the contacts of the female jack (there could have also been some environmental issues at play as well). Almost all cheaply made jacks (especially these days) are made out of some really crappy (impure) metals, and will corrode when making physical contact with other types of metals. Especially when there are currents flowing through them. Thank you for making this video!
great video I watched last night and fell alseep your voice is very soothing, then finished tonight loved it thanks for posting I love making special tools !
Hammer: THANK YOU, for the great set of methodical steps and very practical approach to the repair and your comments. The quick "find/repair" demonstrates a message Dad schooled with often- " mechanical (corrosion and breaks) will be the most likely source of the fault"..... That was a Super Bench TOOL improv, too! Build a couple thousand FOR Sale - Got to be a LOT of modern Plastic Jacks from questionable quality sources that go out just the same.... Sincerely - BDH
Great video . I have found that in many instances TV tuner cleaner will melt or loosen up that turquoise oxidation . Unfortunately I have also found that eventually the only real way to cure this kind of problem is to replace the jacks. Its a lot of work as you know but the fix is worth it in the run. I look forward to checking out more of your videos.
Radio Shack TV tuner cleaner and lube... my secret weapon for years for guitar amps! Different stock #, different formula nowadays, but still available. Just bought a can, but haven't used it yet.
I was working on a Marshall VS100 with the same (real) Cliff jacks. During the diagnosis and cleaning I figured a lil' emery cloth would clean up the oxidized jacks pretty well. Amp owner told me a few days later he was looking online and read NEVER clean Cliff jacks with a heavy grit medium; it will take a "coating" off the metal contacts. Maybe he was trying for a discount... I donno, I was working for free anyway... and he helped me! New caps and the Marshall is screamin'! So scrape at your own peril. (Best just to replace.)
This board looks similar to one of a GK700RB. I replaced a broken Input jack a few weeks ago. It wasnt easy because the board has tiny conducting paths on top and below which can be easy damaged. Replacement Jack: Neutrik NRJ4HF
Right away you should’ve tried patching the cable between the send and return of the effects loop as those normally closed jacks can often get dirty or worn to where they’re not making contact and passing the signal from the preamp to the power section anymore. When you were poking at them with the signal tracer and only getting signal on one side of the tip contacts that should’ve been a dead giveaway.
Nice work. I'm diagnosing a Peavey Valveking 212 right now that has no signal on the lead channel. clean channel is fine. I was just about to type "buy some de-oxit" and as i was typing you mentioned it. LOL
Yep seen this problem before! Dont know how many peavey ive seen with this issue. Ive threatened to pull those cliff style jacks out and use regular old switchcrafts with leads down to the board but never actually have yet.
great! i have a marshall mg30dfx with a problem , when guitar pluged in everything is good after a moment the sound chenged to worse, and when playing guitar load problem can be solved , and then come back!
my roland cube 40 is dead i was plugging it to the wall using a new 3 to 2 adaptor converter the amp with turning on and off because it was loose when i plugged it to the wall while trying plug it right i heard a loud buzzing then the amp went dead fuse is fine nothing burnt in the circuit could it be the transformer or what should i do
Mine lost signal after a cap job I butchered, then fixed (put one cap in backwds and applied pwr; replaced it w/ a new one) Now nothing But it doesn't hum anymore!
ok so what the heck can make the amp, solid state, 2008 Crate .... hum, cant hear it while playing but annoying after not playing. ......... Tried noise gat e but that chokes my guitar, but it does queten the hum. My guitar didnt cause hum on a different amp, so I dont think its the guitar.
I would like to build my own tube amp any help would be appreciated I live in Greenville SC not far from you im thinking a 5E3 circuit and after that a 18 watt never done this before but I am aware of the danger involved I have been studying some pdf's and some schematics although I really not absolutely sure of everything I am looking at on the schematics do have any suggestions or helpful tips at all ty Tony
Good demo on signal tracing. Why not just replace the jacks? $2.50/pc, would take 15min. Only a matter of time before the corrosion comes back. Love your videos man, keep it up!
Thanks Twang. I actually started trying to remove one of the jacks in the FX loop and realized that I was going to have to remove the preamp board to get it out. I opted not to tackle that.
Thank you for the video helped me a lot. I'm presently working on a 1974 Music Man 115 RP, Replaced the bad filter caps, new set of JJ 6CA7's, but there is still something in the preamp cross talking and slightly farting out any suggestions.Thanks
If I'm not mistaken that amp has several integrated circuits (ICs) in the preamp stages, making it nearly impossible to diagnose from a distance. Good luck.
Did you ever find anything on your MM 115 RP crosstalk problem? I have a friend who owns the same amp, and has the same crosstalk problem. He also put new opamp chips in all positions, to no avail. He's pulling his hair out on this problem... Hoping to get some hints to pass on to the man.
It's a long shot, but with my solid state guitar head the light is on when it's plugged in (power switch on or off), and the power switch doesn't do anything, and it will not produce sound
Do you recall how you wired the input jack for the probe? I built the Bill M probe using a .01uf 630V cap and blew up 2 of the Radio shack amps. Bill never shows or mentions if the shielded section of the wire goes to the ground of the 1/8" plug or if the other wire with the clip goes to ground. Thanks very much.
The "tip" of the probe, with the cap in series, goes through the cable (usually the center wire) to the tip of the 1/8 plug. Double check that this is wired correctly. The clip lead ties to the cable shield, which is connected to the ground portion of the 1/8 plug and thereby the ground side of the mini amp. I think you must have something mis-wired if you've blown up two mini-amps (or the capacitor is shorted internally). The capacitor is there to block DC voltage/current from reaching the amp, but it will allow AC (ie. the audio signal) to pass.
I have my probe wired exactly as you described. I tested when I built it and it and it blocked DC (DMM) and passed AC from my Inductance meter which is AC output. I'm guessing that I had a hot chassis because it did work on one amp and popped the Radio Shack amp on another amp. I've since bought and refurbished an old Heathkit T-4 signal tracer but the little RS amp would have been nice to have as well. Thanks very much for the reply.
I bought a Peavey Bandit 112 trans tube 100 watt amp yesterday,the only problem is the pre amp section is not working,I knew that when i bought it,i can plug into the return on the loop function section and use the power amp with a multi effects pedal to adjust my parameters,but i'm just wondering if it would it be worth getting it looked at, and repaired.I only paid 35 dollars for it,other then the preamp section not working the amp is in mint condition,and for 35 bucks i could'nt turn it down,not to mention the speaker alone is worth the 35 i spent.
+Canadian Guitar Hack .. I've read lots of excellent reviews re that amp, so it's probably worth the cost of repair. Try cleaning all the jacks and pots yourself .. you might get lucky. Also, in many cases the problem is a broken solder joint on a jack or pot .. the results of some rough handling & very easy to fix.
HammerToneAmps Thanks for the response i did take it over to a guy around the corner from me,to have a look at it , so he will let me know.and said he would check it out for free.
Very good video - nice use of signal tracing too. I've encountered this problem lots, especially with Cliffs sockets. You'd have found that plugging an instrument lead from the send to return jack, whilst inputting the test signal into the input jack, would have temporarily fixed the problem, indicating the fault. Did you replace or check the dodgy filter cap in the end?
Question, I have a GXL65 CRATE american made solid state amp. It has an semi open back, it has a Crate 12 inch speaker in the back, with no visible damage anywhere on the speaker, or the amp for that matter. I have had the amp stored in a dry and climate controlled area for the time I have owned it. It is about 10 years old. I bought it new. Here is the issue; I have a metalzone 2 BOSS pedal, which I use with this 3 channel amp. This pedal can get a very harsh great metal tone. Lately, while using it, I am noticing some signal noise, like its own distortion interferance that is NOT a part of the normal sound when I have the pedal on. The notes I play sound muddied now compared to the nice distortion sound I was previously getting. The rest of the amp without the pedal is fine, so far. Can you point me in the right direction on what to do? Before I send it to the local Guitar center for a repair??? any help would be greatly appreciate it, it is actually in my profile pic on the lower right there.....Please help?
+HammerToneAmps That is definitely a possibility. I didn't think that first. It sounded so sweet with the pedal, it is crunch heaven, lol, sigh. I will experiment more and try to isolate it more tonight. I really appreciate your help, and thanks!
The thing that happens with them I own one & my wife owned one the Switching button went out EVERY Year on each amp. I used the Boss HM-2 petal that petal has lost it's tone years ago I would chk that petal. But the switching circuit fried on every one of those amps. I have Crate Stealth 50 watt that's never had that issue but Lee Jackson designed it. So of course it's a Gem of an Amp.
I have a 1970s solid state H&H 100 watt guitar amp.UK made,can you tell me what can cause a drop in its volume,it seems to be running at less than half its volume. regards Andrew
