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jakdedert

wrote:
Hi all. Im a newbie to this particular group, one can usually find me
on the Rec.Games.Pinball forums, but I happen to have a querry that
seems would be better suited to this group for help.

I have an older but still beloved Kenwood receiver, (I think it's a KR-
V8070) Early 5.1 surround sound, etc. I had stored it for a while,
but was using it to supply a low level signal for some woofer
repairs.

This particular unit actually has a switch on the back that allows for
changing the stability of the output depending on what the impedance
load of the speakers being used are. I thought I had switched it to
4Ohms so that the individual 4Ohm woofer I was repairing wouldn't do
any damage while I was powering it.

However, it seems I didn't have it switched correctly, and as such,
upon turning up the volume a bit, I ended up blowing the Amp. It
immediately went into "standby" mode, and now no longer operates
properly.

I waited 15 minutes, and retried it, but the receiver is stuck in
standby permanently.

I have plenty of skill in electronics repair, and boardwork, (as I
generally fix Solid State Pinball and arcade stuff) but when it comes
to home audio, Im in the dark as to where to look for troubleshooting
suggestions.

The repair shop looked at it, said it was fixable, but they want $150
to repair it, which isn't worth it to me.

I'd just like to know what to look for, how to diagnose or
troubleshoot this issue and maybe get the part(s) needed to repair it,
and give it a shot.

Can someone point this newbie in the right direction?
Thanks
Vinny

Obviously the problem is in the output section; the first place to look.
Less likely is that the protection circuitry has gone awry. For
either you should get a schematic; but some initial observation is
helpful. Does the unit use discrete output devices (transistors), or
does it use 'chip' amplifiers?

If the chips amps, it's likely one has blown. Replace it and you're
likely finished. It may have multiple identical chips you can sub to
the affected channels (like from the the surround circuitry) for
diagnosis purposes.

If discrete, it gets a little more difficult. It's possible that the
overload took out something further up the line, ie the driver stages.
Still, you might get by testing the output devices and replacing if
defective. Some testing/adjusting is in order if that is the case, even
after the amp is working again.

In either case, since this is a surround amp, you probably have working
channels--if you bypass the 'protect' circuit--which you can use to
compare your findings.

Check the Repair FAQ for more detailed information. Post any specific
findings here; and people with infinitely more experience than I are
likely to give more detailed help.

jak