Randall Amp Problems

[Meat&Beer]

Here's a dumb question...to check for dc voltage for pins 3 and 4 do I put the multimeter leads on both pins at once, or do I put one lead on a pin and the other to the chassis and do that for each pin?

ONE HAND IN THE AMP ONLY!! Don't forget this. A shock across your hand is much more forgiving than that of a shock directly across your heart. Slow and steady hands...

[tanusgreystar]

But if I'm draining the caps first there's no shock right?

[johnnyreece]

But if I'm draining the caps first there's no shock right?

Possibly. Always better safe than sorry. Be sure to check with a meter before sticking your fingers in.

However, to make the measurement, there will have to be power supplied to the circuit. What I like to do is verify that my caps have drained, then use the clips on my meter probes to attach them before turning power on. This does two things: Keeps me from accidentally poking somewhere I shouldn't, and keeps me from hearing the *pop* that always happens when touching the plate pin (and scaring the crap out of me). I HATE that pop...

[tanusgreystar]

I'm having second thoughts about this. I'm probably going to take the amp to a tech. This is obviously beyond my abilities. I just hope it isn't going to cost too much. Thanks for your help!

[johnnyreece]

I'm having second thoughts about this. I'm probably going to take the amp to a tech. This is obviously beyond my abilities. I just hope it isn't going to cost too much. Thanks for your help!

That's a very solid decision. If you aren't in a hurry, you could spend a while familiarizing yourself with how these things work and proper procedures, but if you want it done now and don't really plan on messing with them in the future, might as well let someone else do it.

[Zippy]

I'm having second thoughts about this. I'm probably going to take the amp to a tech. This is obviously beyond my abilities.

I am relieved to see you come to this conclusion.

Thank you for thinking this through.

[tanusgreystar]

You're welcome.

[sluckey]

If anybody actually knows of a documented fatality due to poking fingers into a tube amp chassis please post the document or a link to such document. I personally don't know of any fatalities or even a serious injury, other than it hurts like hell.

I've searched the net and find nada.

[vibratoking]

If anybody actually knows of a documented fatality due to poking fingers into a tube amp chassis please post the document or a link to such document. I personally don't know of any fatalities or even a serious injury, other than it hurts like hell.

I've searched the net and find nada.

Sorry, but that comment is absurd in so many ways. Here's one without even opening the amp.

http://en.wikipedia.org/wiki/Keith_Relf

Really irresponsible and uneducated to imply that it hasn't or can't happen.

IT CAN AND WILL HAPPEN IF YOU DON'T KNOW WHAT YOU ARE DOING

[sluckey]

from that link...

Relf was 33 when he died from electrocution, at his home, while playing his improperly earthed (i.e., grounded) guitar.

Ain't what I'm talking about and you know it.

[ToneMerc]

from that link...

Relf was 33 when he died from electrocution, at his home, while playing his improperly earthed (i.e., grounded) guitar.

Ain't what I'm talking about and you know it.

SL I see your point;however to even faintly minimize the potential of risk by stating the apparent lack of documented fatalities while working on tube amp circuits, yes while might be very low, is at best is irresponsible on a public forum.

The OP like others that have come on this forum has no business inside of a live high voltage DC circuit with virtually no instruction or training whatsoever. You would be looking dumbfounded if he was the first member on his forum to become a fatality.


TM

[sluckey]

SL I see your point

And I see yours too. And I understand and respect your concern. I'm not advocating reckless and untrained procedures around electronic equipment. I'm 65 years old and spent the last 40 years working for FAA on Terminal and Enroute Ground Radar. 20,000v B+ @ 2.5A capacity is something to respect. And I've received plenty of safety training to go along with that career. I don't take the dangers of that occupation lightly.

But, until I started hanging out in guitar amp forums I had never heard of any documented fatalities associated with working on an amp. Still haven't. Yes, it hurts to get bit. I had several in my life. But I was injured more by slamming my hand against the cabinet than I was by the 400V that I accidentally touched.

I'm not trying to down play this at all. But I honestly have never hear of a fatality associated with working on an amp. Maybe there are some known cases out there. But I've searched and I can't find any documentation.

I am hoping this forum would bring any known cases to light. That's all I want to know. I do not intend to ruffle any feathers, but if anyone knows of any fatalities, please post.

Till then, be careful! ...Steve

Oh, BTW... I don't think the OP should be pursuing fixing his amp.

[matt h]

(deleted)

[Jana]

The absence of evidence is not evidence of absence.

(Who was it that said that?)

[gui_tarzan]

A 120V zap hurts (momentarily) and it makes me very angry. I've never had a 240v zap but I don't want to either. Any voltage higher than that is just stupid-dangerous and no matter if anyone has actually heard of someone dying, knowing the dangers of voltage that high puts me on high alert when I'm working around it.

I have life insurance but that doesn't mean I want to use it. People with no experience with high voltage should not put their lives at risk. I've never heard of or read a news report about someone actually dying from a shock working on an amp either BUT it is possible.

When someone inexperienced admits they're in over their head and takes it to an experienced tech, I have a lot of respect for them for doing so. If they then want to take the time to learn how to work with HV safely, more power to 'em.

By the way, I got a mild jolt while taking a tube out of a XXX head not long ago. I thought I had the caps drained completely but I was wrong. Fortunately it wasn't more than 50-60v. I know what that feels like too.