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Pioneer SX-780 receiver repair help or manual needed

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Jeff Hunnicutt

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Aug 21, 1996, 3:00:00 AM8/21/96
to

I've got an older Pioneer SX-780 receiver that I want to repair. The symptom
is that it powers on fine but the relay never kicks on. I have jumpered
the relay to see that the outputs were good and they are. I did replace
the biamps to no avail. If you have any advice or a manual for this
equipment please get in touch with me. I will gladly take a photocopied
schematic if you don't want to sell. Thanks.

--jeff

Sam Goldwasser

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Aug 21, 1996, 3:00:00 AM8/21/96
to

Check the relay coil with an ohmmeter and/or try disconnecting it from the
circuitboard and driving it with a DC supply. If the relay is good you
have a problem in the protection/startup delay circuits.

--- sam

Ren Tescher

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Aug 23, 1996, 3:00:00 AM8/23/96
to

In article <DwHrFB.G2M....@ecsvax.uncecs.edu> hun...@ecsvax.uncecs.edu (Jeff Hunnicutt) writes:
>I've got an older Pioneer SX-780 receiver that I want to repair. The symptom
>is that it powers on fine but the relay never kicks on. I have jumpered
>the relay to see that the outputs were good and they are. I did replace
>the biamps to no avail. If you have any advice or a manual for this
>equipment please get in touch with me. I will gladly take a photocopied
>schematic if you don't want to sell. Thanks.

This may not be much help, but several years ago I had an old Pioneer
Quadrofonic Rcvr (with a fake oscilloscope on the front panel) that
wouldn't kick in its relay either. I ended up getting a schematic
from Pioneer USA and later found a bad (12volt?) zener diode in
one of the power supplies. It might have take out a resistor as well.

Both the rcvr and Skems have passed on to another owner.

Here's an (old?) Pioneer number
(800)457-2881
have a major credit card to order.

Ren
dona nobis pacem

David Terry

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Aug 24, 1996, 3:00:00 AM8/24/96
to

Maybe the diode across the relay is shorted and the
transister is open.

Seen it B4.

Bye...................................

David Terry
DTE...@INTNET.NET
MYZ...@Prodigy.com
http://www.intnet.net/public/terry/


Larry Sirignano

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Aug 27, 1996, 3:00:00 AM8/27/96
to hun...@ecxsvac.unces.edu

The most common cause of this problem is overheated solder connections on
the regulator transistors. You will see 2 or three transistors in the
power supply area mounted on heat-sinks standing up on the circuit board.
Resolder each lead of these transistors well.

Larry


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