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Which of these things will kill me?

#81
Spidey2112 said:
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.
Click to expand...
With an open primary you’d still get line voyage acrocv the primary leads or terminals.
 
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#82
jackn1202 said:
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
Click to expand...
Okay by your question I suggest you button it up and bring it to someone who knows what they are doing, Electricity kills qualified electricians everyday. If this doesn't change your mind I don't know what will



The US Bureau of Labor Statistics (BLS) first began to compile its Census of Fatal Occupational Injuries (CFOI) in 1992. This actual count of on-the-job injuries and illnesses has since been accepted by the National Safety Council as the definitive census of occupational injuries in the US. Each fatality is verified by at least two authoritative sources such as death certificates, police reports, newspaper articles, etc. In addition, the BLS also estimates the annual number of nonfatal injuries to US workers through its Survey of Occupational Injuries and Illnesses (SOII). The SOII is a statistical estimate of nonfatal injuries based on a survey of more than 200,000 employers each year. The Electrical Safety Foundation International (ESFI) uses CFOI and SOII to distill information specifically pertaining to fatal and nonfatal occupational electrical injuries. The most recent data covers the 20 year period from 1992-2010, but mainly focuses on 2003-2010 data.
 
#85
ssguitar.com
Go here and introduce yourself. Ask your questions. These fine folks will help you out.
It's a lot slower pace than good old TB. You will get an answer about once a day.
Do your best to find a schematic out there in the cloud. They will likely ask for that and maybe some close up pics.
Meanwhile heed the advice you have been given .Though you don't have the high voltages typical of a tube amp, The filter caps TwoFingers described will zap you.
 
#86
Always assume that any electronic appliance can kill you.

Don’t even play with the power cord, you can hang yourself with that if you don’t know what you are doing.

On the other hand, the shock of the high cost of taking a not so good amp to a tech can also kill you.
 
#87
The OP was "given" this amp when he or his friend purchased a bass guitar from a music store. There was a thread on this previously. He didn't say if the amp worked in the store, but I suspect it either didn't work at all or the music store knew it was flakey and not sellable. So to save them the trouble of lugging the thing out to the dumpster, the "wonderful people" at the music store gave it to a customer.

So the good news is, the OP has lost nothing except his time and labor.
 
#89
Crater said:
The OP was "given" this amp when he or his friend purchased a bass guitar from a music store. There was a thread on this previously. He didn't say if the amp worked in the store, but I suspect it either didn't work at all or the music store knew it was flakey and not sellable. So to save them the trouble of lugging the thing out to the dumpster, the "wonderful people" at the music store gave it to a customer.

So the good news is, the OP has lost nothing except his time and labor.
Click to expand...
Nah, they didn’t know. The reason they couldn’t sell it is ‘cuz it weighs 65 lbs and only has a 3 band EQ. And whoops I forgot about that thread
 
#92
pappabass said:
Not sure if this is the answer you are looking for, nothing in the amp will shock you after it has been off for a few minutes. The capacitors discharge quickly.
Click to expand...
This is a false assumption. Some earlier amps did not include bleeders on the various supply rails. While a typical low powered solid state amp may not retain enough voltage to kill you, there are some that use a high voltage rail to power a tube preamp and it was not uncommon for there to be missing a bleeder, and this could kill.
 
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#93
Soooo. I am with everyone else saying you need to be careful but I’m not against an opportunity to learn. First you need to respect the electricity that flows through that amp and take some classes. I do HVAC for a living which is 80% electrical problem solving. If it’s a combo amp check to make sure the wires going to the speaker are good. Make sure the cable you are using to the amp is good and plug the preamp into a different power amp to see what that does. After that based on question you have asked I wouldn’t play with the guts. If you really want to learn to fix amps edgucate yourself but it’s not some magic wisdom someone can just give you.
 
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#94
jpmcbride said:
The only thing you can realistically do is UNPLUG it, wait an hour for the capacitors to discharge
Click to expand...

Not all amps work that way, especially some of the older ones like SVTs and a lot of the big Fenders. They have to have bleeder resistors. And those old amps didn't. The caps can hold a charge for months strong enough to kill you (they discharge DC and not AC, so the amount needed to stop your heart is much less).

Learn your basics.
 
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#95
823B43D9-F8BF-45ED-B6F6-478F02D5CFAD.jpeg

All of ‘em.
 
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#98
OK, I fully understand the whole concept of wanting to get it working.
Being new, with no obvious damage makes it look like it can't be hurt that bad.
Maybe that is the case.
Maybe not.

Ask yourself what is that amp worth to you if it was working.
Subtract what you paid for it, in this case zero.

That is your budget for getting it repaired.

If you can't find a tech that will take it in and expect to fix it for less than that amount,
donate it to a school or aspiring new tech looking for something to practice on.
(Hint, there aren't a lot of parts in it, so there aren't a lot that may be bad.
In this case, simpler is better.)
 

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