Yamaha R-900 Receiver Schematic Needed-Relay Problem

Archived from groups: rec.audio.tech (More info?)

Mark,

Unfortunately, I don't have a scan of this schematic. What the failure
most likely means is that the protection circuit IS working, and you
have a bad amplifier channel. Look for DC voltage on the emitters of
the output transistors. One channel will probably be near 0, and the
other will have quite a bit of + or - DC on it., which is what the relay
is there for. It is less likely though possible that the protection
circuit itself has developed a fault.

Regards,
Tim Schwartz
Bristol Electronics


dbacks@attglobal.net wrote:
>
> I need a schematic for a Yamaha R-900 Receiver.
>
> The protective circuit relay has stopped engaging.
> Any advice or assistance is appreciated.
>
> Thanks,
>
> Mark

Archived from groups: rec.audio.tech (More info?)

<dbacks@attglobal.net> wrote in message
news:1105029153.882929.207500@z14g2000cwz.googlegroups.com...
> Hi Tim,
>
> Thank you for your reply.
>
> I have not had a chance to check the Yamaha, however I do have a
> Marantz 2330B that has DC Voltage in one channel.
> So, from a novice, what would dc voltage indicate?
>
> Thanks,
>
> Mark
>

(Butting in....)

If it's the full rail voltage, could be a bad transistor, preamp transistor
pair, bad resistor, bad cap.

Intermediate voltage I'd lean more to a bad cap (feedback circuit)

Mark Z.