In article ,
Don Pearce wrote:
Here's the diagram of the offending amp.
http://s139.photobucket.com/albums/q...kies/A2070.jpg

Ah, they have followed the application note in the data sheet

http://www.datasheetcatalog.org/datasheet/nec/UPC1225H.pdf'

Right. ;-) They are only the surround effects amps - the main ones are
much more beefy MOSFETS.

pretty well. They have dropped some of the good stuff, though, that
could well do with going back in. The output stability choke and
resistor plus Zobel network, for example, which you will find on page
10. Anyway, there are not too many bits to check, the bases and
collectors of all those transistors will do, and compare them with a
good channel. Most likely it is the IC that has keeled over.

Wonder if they could be hooting if there's no Zobel network? That could
cause the protection to operate. I'll have to dig out the scope.

--
*Being healthy is merely the slowest possible rate at which one can die.

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