"John Keiser" wrote in message
...

"Arfa Daily" wrote in message
...


"John Keiser" wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned fine. Today, while playing a CD, suddenly stopped after 5
minutes on low setting. Toggled to mute, loudness, no joy. Using FM
input, controls seem to work and I can hear music when I reach very high
settings. Sometimes crackles to very loud but only momentary. I think
pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have no schematic. Before I tear in blindly, does anyone have access to
a schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.


The service manual is available for free here

http://www.hifi-manuals.com/Pioneer

You need to create an account, but it costs nothing. Your problem sounds
possibly power supply related to me. Mr Cook quesried the fact that you
do not appear to be recording any low negative rails, and that would also
be a concern to me. If you look on the first schematic towards the top
left of the enclosed area marked "POWER SUPPLY CIRCUIT", you will see a
pair of low rails (+ / - 15 v ) marked

"( EQ.AMP TONE CONT. VCA IC) " The +15 v reg is a 3 terminal 78
series, but the negative regulator is discrete, constructed around a pair
of transistors. I would suggest that it might be a good idea to check
that those rails are both present, and finding their way to the indicated
bits of circuitry. Now comes the tricky bit. The schematic, although a
perfectly complete and valid looking one, sadly has no component refs on
it, which is going to make finding those devices a bit more of a hunting
trip, than would otherwise be necessary. Strangely, however, the PCB
overlay diagrams are fully annotated ...

Arfa

Sorry about top/bottom posting thing. Maybe this is on the bottom? I just
use OE to read, rarely post.

The schematic is complex but a big leg up.

Thank you all.

.

Yes, it does look a complex schematic, but at least it's in pdf format, so
fully scalable. Are you aware of the 'tile large pages' option that is often
offered by printer drivers ? This allows you to print the diagram over four
or six or how ever many you like pages, complete with a user definable
overlap, and cutting marks if you want them. This allows you to print a
complex one page diagram like this, at any size that suits you like A3 or
A2. With the overlap and cutting marks, it is a breeze to then tape it
together into a single large sheet.

On the top / bottom posting thing, yes, your last is conventionally
bottom-posted. It just makes it a lot easier to follow a long thread with a
lot of replies from different people, if everyone is following the same
posting scheme. It's different with replying to emails, because it's only
between two people, and each already knows what the other last said, so
top-replying is convenient for that.

Good luck with the Pioneer. It would be interesting to know what you find in
the end.

Arfa