Which of these things will kill me?

[Jim C]

And don't forget the ever popular:
It's not speed that kills you.
It's the sudden stop.

 

[Tim Skaggs]

As far as I can tell the amp head works, but one or both of the leads to the speaker are dead.

What method are you using to tell the amp head works, or what indication is there that tells you the amp head works?

By the way, multiple things inside the amp can kill or hurt you. The small cylindrical things bite harder than you would expect.

 

[ObsessiveArcher]

If you have to ask, I suggest your rule of thumb is "anything with a wire attached."

^^^ This ^^^

 

[agedhorse]

Absolutely nothing, if you unplug it and flip the power switch on.

How does this work? There's a diode bridge preventing accumulated charge stored in the capacitors from discharging through the path you propose. If there are no bleeders, the caps will not discharge under this method. False sense of security (for this anyway).

 

[Rip Van Dan]

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.

The big round shiny thing is known as a toroidal transformer. It is what generates the power and if it is not hooked up, nothing will work. By the way, they are normally very good transformers.

 

[AudioTaper]

Wow, lots of good advice and some questionable comments.
A few things...
- The Toroid transformer is a step-down transformer, not a step-up. It wont hurt you unless its plugged in and the power switch is on while you touch it, or you drop it on your foot (plugged in or not)
- Do not use conductive prodding tools. No pencils or knives. I use wooden dowels. Someone mentioned a fiberglass one, awesome!
- Do not trust that a cap will bleed off in an hour, or that it has a functional bleeder diode or resistor at all. Use a shorting resistor (1K Ohm 3W is what I usually have) and verify that it is not storing a charge with a screwdriver and a meter (don't discharge the caps with the screwdriver) I worked on a Peavey Mace 150W all tube combo for a customer years ago and didnt verify that all the cap banks were fully discharged. I cooked my finger on 480VDC stored by a separate bank of caps. A quick verification with the meter would have saved some embarrassment and pain.
- I would recommend to not poke around inside an amp if you dont know what you are doing. There are videos online, books, and classes to teach basic electronic theory, check those out first. You can get a multimeter for about $40 that will do a lot of what you would need. I have seen oscilloscope kits on Ebay for about the same. It wont break the bank to get some good tools and get started if that is something you are interested in. Look for a meter with a diode check function (most have them) and preferably a scope with X-Y inputs so you can make a basic curve tracer.
-Check the speaker out with a known working amp.
-Just because a wire has insulation doesnt mean that the insulation will protect you if you touch it. There may be splits or cracks.
-Mentioned above, only 1 hand in the amp when its powered on. My left hand is kept in my pocket for safety and also wedding rings are conductive.
-if all else fails, the trash can may not be such a bad idea after all.

 

[JimmyM]

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.

Jackn, eh? I get it.

 

[IamGroot]

I got kicked across the room when I crossed a capacitor in an older style camera flash attachment. Made a believer out of me. And i have been zapped by my electric fence numerous times.

 

[byacey]

And i have been zapped by my electric fence numerous times.

Years ago my brother had a fencer that crapped out, so I offered to build him one. He laughed and said "No way! The way you build stuff, the cattle will have to huddle in the middle of the pasture. If they take a few steps towards the fence, a big arc will jump from the fence to the animal and take it out!"

I had to laugh at the mental image he painted.

 

[IamGroot]

I swear cows could smell the electricity because they would knock down a wire within a couple of hours after it shorted out.
Mine was a weed chopper.
After the second grass fire, I quit using it. Cowbirds would get cauvht in it and their dangling feet would start the fire.

When the wire shorted out due to wet grass after a rain, i would go clear the grsss with a weed wacker and then use hamd signals for my wife or kids to reconnect the gap. They screwed up and i got zapped several ltimes.. worst was when i was standing in a puddle and had a crack in my work boot. It threw me. Another time, i was working shirtless and leaned over and it burned the hair off a spot on my chest.

I also had a car battery powered model which was pretty benign.

 

[Thumpin6string]

Before diving into this with no knowledge, it might be smarter to test the simple things first. Does it have send and return or preamp out and power amp in jacks? If so, jumper them with a patch cable and see if you have output. Dirty jacks are the most common problems. If no luck there, run a cable from the preamp out to the power amp in on a known working amp. If that works, you know the preamp works. If not, it's a preamp issue and is tech time. You can do the opposite of that and run the pre out of the good amp to the power amp in of the FREE amp and see if you have output. If not, then it is a power amp issue and needs to go to a tech. Unless you know how to test and read a schematic, you will be wasting your time and risking hurting yourself or ruining the amp.

 

[Axstar]

The big round boy that looks like a wrapped up burger can definitely deliver some spiciness when required.

 

[Hand slap]

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.

View attachment 3294702

Actually the most dangeruou part of THAT amp, is the 120 AC coming in, that goes to the (PRIMARY OF THE TRANSFORMER) love your description of the problem. My last customer told me “my amp works, and everything, there’s just NO SOUND”

 

[Slevage]

Absolutely nothing, if you unplug it and flip the power switch on. Electronics, of any form, are only dangerous if there's electricity in them. Unplug it, discharge the residuals. Safe.

The “ discharge the residuals “ is the tricky part”.
Unplugging it and turning the power switch on closes a switch to an already open circuit,
Beware of newer stuff with switching power supplies. The “residual stuff” in those amps can remain loaded with 340 volts DC.

My favorite bumper sticker starts with:
“wiring is not a hobby.............”.

 

[Spidey2112]

Even if you found a chared part, that could be the result of another failed part that doesn't look bad.

So true... currently, we have no power up, for our drummer's Behringer HA4700 multi channel headphone amp. Nothing charred, though...

The first thing I ohmed out was the fuse (checked good)... pretty cool, too... the fuse block was reversible for 120 VAC, as well as 240 VAC, and yes I made sure it was correctly installed. Then I measured the power cord (checked good). With no schematic, I measured from power receptacle to power switch (good). I powered the unit on, measuring the other side of the switch (switch passing 120 VAC). This wire went straight into the primary of the toroidal transformer... it should be coming out of the transformer on the other leg (which is fused), right? It wasn't.

Powered the unit down, and isolated the transformer to check for some type of ohm reading, other than shorted or open. With power switch off, and fuse block removed, I measured the primary... and got nothing.

I'm calling a bad toroidal power transformer, with an open primary... it's on it's way from Music Tribe, today.

And I didn't change one capacitor... now, if I could only get better at ordering parts.

 

[levis76]

Best case scenario, you don’t break it more than it already is.

Worst case, you break it more and you end up in the floor needing EMS.

Electronics is not something you’re just gonna pop the hood on and see what the problem is. Even if it’s a lead that came off, do you know exactly where it goes and have the proper tools to reattach it? Do you have a DVM to do live-dead-live testing to ensure it’s safe to work on?

Take it to a tech.

 

[bassinflorida]

I keep tuning into this post. Can't look away!!

 

[dbase]

Is the OP still with us?

 

[interp]

I suspect that if it were dropped on your head from a great height that toroidal transformer might do the trick.

 

[agedhorse]

Do you have a DVM to do live-dead-live testing to ensure it’s safe to work on?

At first I read DVM as Dr. of veterinary medicine, which made the second part more creative!