(audio) "PA amp"?

[Rich Grise]

I had the same experience until I started making things that were
exported to third-world countries.

A couple of contracts ago, I was working at a factory, and the mains
lost a phase. It was hardly noticeable, except for 1/3 of the lights
at about half-brightness, half of the computers started spontaneously
rebooting, and the compressor motor caught fire. The power company
reimbursed _everybody_ that had equipment damaged by the semi-failure.
(it was a local tranny, about a couple-block area).

Cheers!
Rich

 

[Mike Page]

Maybe you made a resonant load ?

Graham

It didn't happen every time, seemed to have been more of a startup
problem. I didn't have a bleed across the caps, so I guess they could
have got biassed more than the 100mV expected (due to transformer inrush
or something) and run the output stage in partial class A. Anyway .. it
was only a bit of test gear and not worth making perfect. All I wanted
was 500V at low distortion into 3M or so. Now we have a calibrator, but
the frequency control is not too clever.

Regards,
Mike.

 

[ge]

Thanks for all the responses. A couple of questions:

1. Is a "PA amp" just an audio amp with a transformer, or something
substantially different?

2.

Why do i smell smoke at the end of this experiment?

Perhaps you've seen my work. A good argument for not using a backward
variac.



3. Would this work better if we used those fat speaker cables?


George

 

[Pooh Bear]

I had the same experience until I started making things that were
exported to third-world countries.

Yup - that'll do it.

A company I worked for had no end of trouble with equipment exported to
Nigeria. The overvoltage there can be astonishing.


Graham

 

[Ken Smith]

A company I worked for had no end of trouble with equipment exported to
Nigeria. The overvoltage there can be astonishing.

In China I saw:

260Vac @ 47 Hz in the morning

160Vac @ 45 Hz in the after noon

On the same 220V 50Hz outlet.

 

[Paul Hovnanian P.E.]

In China I saw:

260Vac @ 47 Hz in the morning

160Vac @ 45 Hz in the after noon

On the same 220V 50Hz outlet.

Or somebody will run your product off a portable generator with a bad
speed governor.

 

[SioL]

In China I saw:

260Vac @ 47 Hz in the morning

160Vac @ 45 Hz in the after noon

On the same 220V 50Hz outlet.

They must be late for work every morning

For a while most alarm clocks used mains as freq. reference.

SioL