Even if you unplug it the capacitors hold a charge. I was reading online that it can be very dangerous to work on them if the capacitors are not fully drained. I don’t have a tube amp, I have a cheap piece of shit I found at a thrift store for $20. I don’t want to risk death for this amp, it’s a cheap piece of shit; even if I got it to power up again, it would still be a cheap piece of shit. But I’m also a cheap piece of shit, so I don’t wanna just throw away $20. I saw some various ways of draining the capacitors, but I’m afraid to even open it up with out having a better idea of what I’m doing. Any suggestions?
What’s wrong with it; what’s it doing/not doing?
(Warning! Don’t kill yourself and blame me!) If this is your average solid-state amp, the danger is not very great. Old CRTs operated at much higher voltages and they could really kick you on your butt. I’ve worked on a lot of “piece of shit” amps and never really worried about discharging the caps. In fact, trying to discharge the caps when you don’t know exactly what you’re doing is more likely to cause other problems in the circuitry than protect you. Now, a NICE amp may surprise you when you poke around in it (as well as screwing up the circuitry).
Make and model would help a lot.
It won’t turn on, I think I blew a fuse, but maybe that’s just wishful thinking - I can’t solder for shit. It would turn on and have really crap/nonexistent base when I first got it. Then I started running it through a mixer from a piece of crap drum kit on the input and into headphones on the output. I’m a shitty drummer also, I’m not sure if that factors into the equation.
Do not do this.
Mr Lightning is our Friend, until he isn’t.
it depends where the capacitors are. if they’re in the power supply section, they’ll be somewhere around mains voltage (120V, assuming you’re in North America.)
if they’re in the audio section, they could be anywhere from 12-40 volts.
tube amps were the dangerous ones because they had plate voltages in the range of several hundred volts.
If it’s solid state, then at the most you could have around 170 V on some caps. But they’re likely discharged by now.
Unplug the amp. Then turn on the power switch and fiddle with all the knobs and other switches - doing this will very likely discharge the caps. After you take it apart, identify the power supply caps and discharge them for good measure.
you’d be hard pressed to be able to disconnect it from the power supply & start messing with it quickly enough to get any type of tingle, much less shocked.
test my advice by shorting something metal across it’s leads, remember though - with the power disconnected to it.
did you see a spark? no.
did the metal you used to short the capacitor heat up? no.
there are surely capacitors that could get someone pretty good, i just don’t think you’ll find many with the capability to do anything in consumer electronics that have been unplugged, especially after a minute or so.
I’ve been lit up before with a 10mfd/120 volt cap for a fan motor that operating. I’ve been shocked several times over the years. that one would’ve killed me if i were older or in worse shape physically.
Fuses usually aren’t soldered in, they fit in clips or sit in a holder with a screw-off cap.
Like beowulff said, a brand name and model would be a big help.
^ Example: Fender Princeton, model #THX-1138. Model number found on a plate near the AC cord.
I know that much, that’s why I hope it’s just a fuse and nothing else. My soldering skills are shit, probably get a bunch of cold solders and what not if I had to do a more involved repair. Sorry about the delay, but I’ll get back to you with the model; I’m in bed now - if i start rustling around to much my wife might wake up and she’d be especially pissed since Aunt Flow is visiting this week.
Heat the part, not the solder. Heating the solder is what often causes cold solder joints. Heat the part, let the solder flow onto it. That will make a much better solder joint.
Also, make sure the tip of your soldering iron is clean. Use a wet sponge to keep it clean. Tin your soldering iron (put a bit of solder on it) but don’t put a big glob of solder on it.
Fuses generally don’t just pop on their own. Even if you do find a bad fuse, there’s a good chance you’ve got some other issue as well, like a bad tube or capacitors that are dried out and failing.
The crap/nonexistent bass makes me think bad capacitors or a bad ground (signal return) somewhere. You may have more than one problem here.
I’ve always found this advice somewhat misleading.
When I solder, I feed the solder into the corner formed by the soldering iron tip and the part being soldered. Many times, the solder won’t melt very easily until some of the flux coats the work. Pre-melting some solder helps with heat transfer.
It says T-Power on it, but other than that, I can’t find any sort of model# on it; it’s not in any of the places a model# usually would be. It’s made in Korea, I don’t know if that particular piece of information is useful, but it’s all I got at the moment.
I took it apart, I’m not dead yet. The fuse is busted and it looks like at least one of the capacitors is bad - it has some nefarious looking brown stuff on it. I was gonna just replace the fuse and see what happens, but then I was wondering if I should also replace the capacitor before powering on and testing.
Bad caps are the #1 cause of power supply failures. Replace it.
Don’t do this. You may damage the capacitor. (and definitely the screwdriver you’re shorting it with)
Proper practice is to put a 10-Ohm wirewound resistor of several watts rating across the capacitor for a second or two. Thus the current is limited.
IANAE; many (many) years ago I was fiddling with capacitors and a 9-volt battery. I’d connected the capacitor a few times, then I accidentally shorted it with my finger and got a strong shock. But - this was capacitors in the size of a 35mm film can give or take. This or bigger is what you’d find in tube equipment and really old PC’s.
Today, unless you bought a 400-watt amp, you’ll be fine. unplug it, let it sit for a minute, then try the short trick with a screwdriver you wouldn’t be sad to lose. (I had a friend who tried to fix an electrical outlet - it left a small semicircular hole in his knife blade while he removed insulation, because the electricity in the house was backward, the neutral as the live, so the breaker didn’t kill the power. That’s 120V, lotsa watts) Anything smaller around than your thumb, you are more likely to get a nasty shock unless you give it a minute to drain. Bad capacitor - probably no charge anyway.
There was a problem with capacitors about the early 2000’s. Someone in Taiwan sold a huge number of electrolytic capacitors containing a faulty fluid (allegedly someone else sabotaging an attempt at industrial espionage by feeding the wrong list of ingredients for the electrolyte). So any seriously bulging or leaking electrolytes could be a problem.
Also as a hobbyist friend of mine found many years ago trying to fix an early computer of mine (adding memory) - there are soldering irons and there are soldering irons. the ones for heavy duty work may be too powerful, dump too much heat and damage more advanced electronics. My friend had the traces lifting off the circuit board of my Commodore Pet while trying to add memory. Fortunately, he was careful after that and it actually worked. Watch that you are not overheating the board and components when trying to solder. (or unsolder, to remove the bad capacitor).
Well that’s good, and always preferable to the alternative. 
It’s hard to tell without looking at it, but I suspect the brown stuff used to be inside of it. Definitely replace the cap.
There is probably a rectifier bridge or possibly some discrete diodes in the power supply as well. As beowulff said the cap is your most likely point of failure, but it may have taken out the rectifier when it went, or possibly the rectifier went first. You can check the rectifier with a multimeter as long as your meter has a diode check function.
I put it back together and I’m still alive. I changed the fuse and it powers on now, but it sounds the same as before I had the problem with it not powering on - which is acceptable to a degree but with terrible bass. I mostly just use it with headphones, so I’ll see how that all works tomorrow.
Oddly enough, my multimeter was stolen a few months ago. Noone just stole the multimeter in case you’re wondering, it was in a bag that someone stole out of my car. I used to bring it to work in case the work issued piece of crap failed me in the field. I haven’t found any at thrift stores yet, and pawn shops only ever seem to have super high end ones. Moral of the story is never get an expensive looking bag.