Panasonic SA-HE200 receiver/amp -- overload

[Michael]

This Panasonic SA-HE200 Receiver/Stereo/Amp came in with the display
indicating "overload" and "turn power off" a few seconds after the power is
turned on.

Has anyone had experience with this symptom or do you have a service
manual/schematic?

Some background:

According to the owner's manual, the panel indication suggests a shorted
speaker terminal, too low impedance speakers, overdriving, or high heat
conditions, all problems at or after the final amps. However, the symptom
appears on a cold start up without any external connections. I've ensured
there are no stray bits of speaker wire shorting the terminals and checked
back to the main pcb for shorts.

The intregrated outputs (IC 601 and 602) are 24 pin RSN310R37 multi-channel
mosfets. I did a left-right channel terminal-by-terminal check of
resistance and voltage and they are the same (of course, it could be a
problem common to both). Main power to the amps is plus and minus 56V,
consistent with the 63V filter caps. I have not been able to find any data
on the mosfet IC.

Michael (C.E.T.)

please post reply, thanks

 

[Mark D. Zacharias]

This Panasonic SA-HE200 Receiver/Stereo/Amp came in with the display
indicating "overload" and "turn power off" a few seconds after the power
is
turned on.

Has anyone had experience with this symptom or do you have a service
manual/schematic?

Some background:

According to the owner's manual, the panel indication suggests a shorted
speaker terminal, too low impedance speakers, overdriving, or high heat
conditions, all problems at or after the final amps. However, the symptom
appears on a cold start up without any external connections. I've ensured
there are no stray bits of speaker wire shorting the terminals and checked
back to the main pcb for shorts.

The intregrated outputs (IC 601 and 602) are 24 pin RSN310R37
multi-channel
mosfets. I did a left-right channel terminal-by-terminal check of
resistance and voltage and they are the same (of course, it could be a
problem common to both). Main power to the amps is plus and minus 56V,
consistent with the 63V filter caps. I have not been able to find any
data
on the mosfet IC.

Michael (C.E.T.)

please post reply, thanks

I'm still thinking it's an output IC, in spite of your voltage readings, but
some of these Panasonic units also used an STK voltage regulator - seen some
problems with those....

Panasonic service manuals typically aren't too expensive - their US phone
number is 800-833-9626.

Mark Z.

 

[Michael]

Mark Z:

It could indeed be a defective 3-channel output IC (there's two of them).
But at over $US75 each, it'll be worth the effort get the diagnosis right
the first time

Probably best to figure out what the self-test system looks at that would
give an "overload" display (and, incidentally, turn the cooling fan on).
I'm working on that, but in the meantime, the service manual has been
ordered. Tnx.




"Mark D. Zacharias" wrote in message

 

[Michael]

With the schematic in hand the problem was positively traced to a defective
overload/overheat circuit within one of the two three-channel IC's.

Mark Z, you were correct, and yes, the manuals are very reasonably priced.
Thanks.

Michael