This is the inside of a Stagg 500BA 115 solid state amp head. Which of these parts will kill or hurt me? As far as I can tell the amp head works, but one or both of the leads to the speaker are dead.
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Which of these things will kill me?
- Thread starter jackn1202
- Start date
If you have to ask, I suggest your rule of thumb is "anything with a wire attached."
Well. If you have to ask the question, don’t you think it’d be a good idea to take it to someone who knows what they’re doing?
That being said, (and I don’t know for sure) but I’d stay away from that big circular foil covered monster in the middle.
That being said, (and I don’t know for sure) but I’d stay away from that big circular foil covered monster in the middle.
You're good to go. Dive right in. Only the stuff with wires attached can kill you. But you can touch anything else. 
Clarification: just looking for advice from people who can give it. I already know that I “should” be taking this amp in to a qualified amp tech. However, this is a solid state, and I’m under the impression that it is far less dangerous than a tube. I’m also very broke, I got this seemingly brand new amp for free and aim to keep it free so that I can give it to a friend.
That being said, I did assume that the big shiny round thing would hurt a good bit. It’s not plugged in or anything, I didn’t think any components of a solid state retained electricity like a tube except for maybe that thing.
That being said, I did assume that the big shiny round thing would hurt a good bit. It’s not plugged in or anything, I didn’t think any components of a solid state retained electricity like a tube except for maybe that thing.
Search for and download the schematic.
Post it here. Wiser people than I will chime in.
That tinfoil disc monster is likely to be a high voltage toroidal transformer.
Post it here. Wiser people than I will chime in.
That tinfoil disc monster is likely to be a high voltage toroidal transformer.
Assuming you get a “nothing will harm you answer” you’re looking for, what do you intend to do? Do you really trust your life with the internet?
What’s the issue with the amp?
Anybody qualified to give advice will tell you the exact same thing with varying degrees of compassion and comedy. There's a reason most of us call it magic smoke when it gets out. Once leaked it can never be put back in without intevention by a magician, I mean technician.
Ok, serious answer time....
Caps (capacitors) can retain juice. They need to be drained. You can easily use a resistor to drain them. The caps in that head appear to be the cylindrical shaped black things in the middle. But caps come in all sizes amd shapes, so there could he others.
This assumes the ampnos NOT plugged in. Once plugged in, there's no telling without a schematic.
This is still a horrible idea to go poking around in it. I have some education and training in electronics and even I wouldn't just "start trying to figure out" what was wrong with an amp with no schematic amd no description of the symptoms that occurred just before the amp stopped working.
I know you want to give your friend an amp. Give it to your friend and tell your friend to take it to a tech.
Caps (capacitors) can retain juice. They need to be drained. You can easily use a resistor to drain them. The caps in that head appear to be the cylindrical shaped black things in the middle. But caps come in all sizes amd shapes, so there could he others.
This assumes the ampnos NOT plugged in. Once plugged in, there's no telling without a schematic.
This is still a horrible idea to go poking around in it. I have some education and training in electronics and even I wouldn't just "start trying to figure out" what was wrong with an amp with no schematic amd no description of the symptoms that occurred just before the amp stopped working.
I know you want to give your friend an amp. Give it to your friend and tell your friend to take it to a tech.
While we all die eventually, I suggest seeking a local qualified technician.
just a reminder to film it for a possible viral youtube clip...
Passinwind
I know nothing.
- Dec 3, 2003
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- Designer/Toaster Tech @ Passinwind Electronics
None, if you don't mess with them. But perhaps a much better question is: "which of these currently functional parts will I destroy attempting to fix this amp?"
How did you deduce that?
Tongue test - just like 9V batteries but you lick capacitors instead. Whichever one knocks you out was good...
Aight these answers are making me laugh now. I didn’t realize caps could retain electricity as well, so that’s good to know. I guess I’ll just test a couple leads and if none of the things I know I can touch (rubber coated wires) will fix it, I’ll probably just get rid of it.
Also, someone asked how I came to the conclusion that the head worked but wasn’t sending signal to the speaker. Basically, I listened for normal amp noises. When I turn the amp on, the head itself seems to make all the right noises. I flip the switch, there’s a click, and then a small amount of hum that doesn’t seem any more or less than my other amps. However, there is no pop from the speaker. I’ve switched out the speaker for another one and tried, but to no avail. When I plug in a cable and touch the end with my finger, no buzz or pop. So I could still be wrong, but this is what I came up with.
Also, someone asked how I came to the conclusion that the head worked but wasn’t sending signal to the speaker. Basically, I listened for normal amp noises. When I turn the amp on, the head itself seems to make all the right noises. I flip the switch, there’s a click, and then a small amount of hum that doesn’t seem any more or less than my other amps. However, there is no pop from the speaker. I’ve switched out the speaker for another one and tried, but to no avail. When I plug in a cable and touch the end with my finger, no buzz or pop. So I could still be wrong, but this is what I came up with.
If the mains fuse hasn't blown (and it sounds like it hasn't) and you have tried a different guitar lead and speaker then without a schematic, a pile of test gear, and some considerable knowledge of how amps work then you have reached the limit of what you can do without the risk of introducing more faults.
Thought for the day - If amps were easy to fix there would be no need for amp techs.
Thought for the day - If amps were easy to fix there would be no need for amp techs.
Unplug it before diving in and you might just live to tell your grandchildren about it.
At a glance, 2 power amps on opposite sides (top and bottom). EQ and controls up front (left side) . Heavy round step-up transformer and the circuit just above it (rectifier and filter caps) form the power supply. You can touch anything insulated, but be wary of metal connections etc. OK to poke at bare wire and metal connections with an eraser at the end end a pencil (fingers at length) . A volt meter referenced to ground (the chassis) can help identify where ominus voltages reside. Even unplugged, those filter caps can store a good charge. Enter cautiously if you are inclined to. If you can obtain a schematic, that would be very helpful.
You might try some standard trouble shooting like sending the pre-amp signal from this amp to the power amp of another and vice-versa. I'm sure other people can give you more ideas. I can't count the number of times someone on this forum has found out the only problem they had was a corroded jack that was fixed by Deoxit in a few seconds.
You'd be wrong about that.
Wrong again. The "big shiny round thing" is a torodial transformer, and supplies power to the amp. It does not store electricity. It could seriously mess you up if you left the amp plugged in and touched it or anything connected to it. The slight hum you hear on turn-on is electricity flowing through that thing. There's some other parts in there that can hurt you. There are some that you can hurt easily.
This is literally the definition of what a capacitor does; store electricity. You've just failed Electronics 101. Put the thing back together and...
I would do that last part.
And seriously, since you have the itch and ideas of how to go about doing something (albeit bad ideas, but still, you're thinking) I would go take a basic electronics course someplace nearby and at least get down the basics. I think you'd do good at it, and it will help at least keep you from killing yourself, or far more likely, as I did as a kid, destroying half the electronic stuff in the house or setting the thing I was working on fire. Both of which happened multiple times. A class would have been a lot cheaper.
