• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Safe touching of live circuitry inside amps

A couple times in the past I've put a short clip lead across the filter caps to keep the voltage at zero while making measurements. A couple times in the past I've forgotten to remove it before applying power.

Make sure your practice allows for completely unexpected stupid stuff. I once had a power switch on a customer unit that had a piece of broken metal inside. It connected hot to a floating chassis. Lucky the scope ground survived. And me.
 
I've had quite a few amps/receivers come through with coins, washers, and even loose screws inside of them. It's amazing how many of them weren't burned to a crisp. No hot chassis stuff though. I don't really work on tube amps.
 
OBMG74 said:
Ok, confession time.
How many of you own a notched pair of these from cutting a live 120V wire by mistake?
Unfortunately, I do and fortunately have not repeated that stupid mistake.
Click to expand...
Nope, not me. Mine had green handles.

Laying under the sink, installing a garbage disposal (in my late 20's), when realizing I needed a pigtail to power it up. The outlet my trouble light was plugged into had the perfect solution. Bonehead move by me to snip off the end of the trouble light cord (yes, while live) and bang. I still have those side cutters, but they are in the loaner tool box.
 
 
restorer-john said:
The other was my totally my fault. I had NO idea that MAIN switch on a breaker panel did not include the electric hot water system. Flicked the main, checked the live/s a proceeded to get a hit across both arms when removing the faulty HWS breaker.
Click to expand...
Did the electric hot water system bypass the circuit breaker board? Who wired that?

Wow!
 
I think the worst I've done is when I mistakenly used a 50V electrolytic capacitor when I should have used a 500V rated cap.
I fired the amp up, it was nice and quiet. As the tubes started to conduct and started to pass sound, that cap exploded. It made a big stinky mess with the guts of the capacitor splattered all over the inside of the amp. Think big smelly party popper. :D
 
Lavane said:
I think the worst I've done is when I mistakenly used a 50V electrolytic capacitor when I should have used a 500V rated cap.
I fired the amp up, it was nice and quiet. As the tubes started to conduct and started to pass sound, that cap exploded. It made a big stinky mess with the guts of the capacitor splattered all over the inside of the amp. Think big smelly party popper. :D
Click to expand...
You know something is funky when the dim bulb tester initially gets bright, then goes dim, then gets really bright again.

69aa2b69-5125-4e47-b0ca-b36be0abd85e.png
 
Mr Boochie said:
Did the electric hot water system bypass the circuit breaker board? Who wired that?

Wow!
Click to expand...

I can't speak to that situation, but I have some load management circuits (water heater bring on) that run off a separately metered panel having its own main breaker. If one didn't really know that and just turned off the "Main" main panel thinking the load mangement panel was a subfeed, you'd be in for a surprise.
 
OBMG74 said:
Ok, confession time.
How many of you own a notched pair of these from cutting a live 120V wire by mistake?
Unfortunately, I do and fortunately have not repeated that stupid mistake.
Click to expand...
not those, but a screwdriver that I did it with not long ago. Shut the breaker off, opened up the outlet to replace it, didn't verify that the power was off, and sure enough it wasn't. Two breakers in the panel, I got the wrong one. I picked the one labeled "outlets", well that specific outlet happened to be on the one for "lights" for some completely unclear reason.

this was 2 weeks ago, so its not like I can claim it was some mistake I made long ago when I didn't know better.
 
Mr Boochie said:
Did the electric hot water system bypass the circuit breaker board? Who wired that?

Wow!
Click to expand...

The electric hot water system is controlled supply (off peak) with it's own meter in the breaker panel. It's turned on and off with ripple control outside of peak times and costs less per kWhr than normal electricity. So, apparently when installed 30+ years ago it bypasses the Main switch completely, even though it all comes down the one supply cable.

I turned off the Main switch (and all the other switches), checked neither meter was moving and put a non-contact sense device on every active I could see and all were dead (or so I thought).

Because the ripple control switch was "off" at the time, the HWS meter wasn't moving anyway, but it's supply side, and the faulty breaker was actually live and I missed it. It may have switched "on" via ripple control whilst I was replacing the breaker. You only do that once.
 
Last edited:
restorer-john said:
The electric hot water system is controlled supply (off peak) with it's own meter in the breaker panel. It's turned on and off with ripple control outside of peak times and costs less per kWhr than normal electricity. So, apparently when installed 30+ years ago it bypasses the Main switch completely, even though it all comes down the one supply cable.
Click to expand...
Is this legal in your neck of the woods?

Maybe the heater runs on 220 VAC, and whoever installed it didn't know how to modify the box to add a 220 VAC outlet.

:idea:
 
You must log in or register to reply here.
Back
Top Bottom