In article ,
Phil Allison wrote:
Dave Plowman (Nutcase) wrote:

Pretty basic MOSFET power amp.

I'm used to it thumping at switch on. No speaker relay in this basic
design.


** You posted the same here in December last year.

About switch on thump. This is at switch off, and a fault.

But one of them as taken to thumping at switch off. Not always, which
makes fault finding more tricky.

Most likely cause?


** Old and bad electros are the cause of almost everything.

They are all relatively new, and good quality. Not to say one can't have
failed. There are only 4 electros in this pretty basic design. Two are
across the supply rails, one on the input, and the most likely one a low
ESR type which is part of a RC network across the speaker output.

But the fault hasn't occurred again.


BTW; anyone familiar with the famous Crown DC300A ?

Both channels would emit a long squeal about 10 seconds after switch off
- it sounded much like a party balloon being let down while squeezing
the neck.

There was a note inserted in later service manuals that *no attempt*
should be made to fix the problem, as any possible fix would render the
amp unstable.




.... Phil

--
*HOW DO THEY GET DEER TO CROSS THE ROAD ONLY AT THOSE YELLOW ROAD SIGNS?

Dave Plowman London SW
To e-mail, change noise into sound.