Pioneer SX-850 Problems

[davesheb]

I have a Pioneer SX-850 receiver. It's a great valuable item and I want to
repair it. When I turn on the tuner, it plays FM for a few seconds then I
hear a ping then it kicks out. If I get back to the tuner it plays for a
few seconds then kicks out again. Does this sound like a relay problem or
something. Also some of my switches don't make contact. I've tried to
take it apart to try to clean or stretch some springs to make better
contact but it is difficult. Are the switches available for replacement?
Any help anyone can give would be appreciated. Thanks.

 

[Sofie]

davesheb:
When the FM "kicks out" does the amplifier section of the receiver still
work with other audio sources OK?
If the problem is really in the amplifier section and not the FM Tuner
circuitry then more than likely the protection relay is energizing, thus the
"ping" you hear.... probably caused by faulty components or dry, cracked
solder connections in the power output and/or driver circuitry.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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"davesheb" <dshebish@comhs.org> wrote in message
news:60dc341d7404ac8aac7fe69454bc6be6@localhost.talkaboutelectronicequipment.com...

I have a Pioneer SX-850 receiver. It's a great valuable item and I want
to
repair it. When I turn on the tuner, it plays FM for a few seconds then I
hear a ping then it kicks out. If I get back to the tuner it plays for a
few seconds then kicks out again. Does this sound like a relay problem or
something. Also some of my switches don't make contact. I've tried to
take it apart to try to clean or stretch some springs to make better
contact but it is difficult. Are the switches available for replacement?
Any help anyone can give would be appreciated. Thanks.

 

[Mark D. Zacharias]

The "ping" you hear is the speaker relay cutting out. On the SX-850 this is
usually caused by a single bad transistor in the power supply, though there
are certainly other power supply issues which can trigger the protection
circuit to cut off the relay.

Cleaning or stretching springs won't make dirty controls work. There are
cleaner / lubricants designed for the purpose, and they need to be used with
an understanding of how the switches and controls are built and how they do
what they do.
One uses a cleaner / lubricant designed for the purpose, such as Caig
De-Oxit, usually in a small aerosol can with a plastic extender tube. With
the valve on the can set to LOW, one sprays a bit of cleaner into the
control, aimed at the carbon element, if it's a potentiometer, or at the
moving and stationary contacts, if it's a switch. Work the control back and
forth numerous times. Usually we repeat the process.

There's other fine points - such as blowing out the dust etc first, and
packing tissue around the control to catch runoff and prevent a mess. Often
it's necessary to hold the unit at some impossible angle so gravity can help
get the cleaner where it needs to be. I will often blow out the controls
again with a compressor and repeat the treatment, it's my belief that by so
doing I blow out some of the debris loosened by the cleaning process.



Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"davesheb" <dshebish@comhs.org> wrote in message
news:60dc341d7404ac8aac7fe69454bc6be6@localhost.talkaboutelectronicequipment.com...

I have a Pioneer SX-850 receiver. It's a great valuable item and I want
to
repair it. When I turn on the tuner, it plays FM for a few seconds then I
hear a ping then it kicks out. If I get back to the tuner it plays for a
few seconds then kicks out again. Does this sound like a relay problem or
something. Also some of my switches don't make contact. I've tried to
take it apart to try to clean or stretch some springs to make better
contact but it is difficult. Are the switches available for replacement?
Any help anyone can give would be appreciated. Thanks.

 

[davesheb]

Yes, the other inputs still work. Only the FM module kicks out. I would
appreciate help with this. You've been helpful so far.

 

[davesheb]

Is it difficult to find the bad transistor? I am send for the service
manual and will probably give it to an experience repair place. Do you
think this would be costly. Is this receiver worth the cost effort. Your
opinion is appreciated. Thanks.

 

[Mark D. Zacharias]

The transistor to which I referred would cut out sound from all sources,
since it is the pass transistor for the relay power supply voltage.

It is a 2SC1438, if memory serves, located near the middle of the regulated
power supply board on the underneath side of the unit.

I can take no responsibility for the use or misuse of this information, and
I hope that only a person of reasonable competence with electronic circuits
will attempt this repair.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"davesheb" <dshebish@comhs.org> wrote in message
news:b84eba60d7a8d204989421afe386f322@localhost.talkaboutelectronicequipment.com...

Is it difficult to find the bad transistor? I am send for the service
manual and will probably give it to an experience repair place. Do you
think this would be costly. Is this receiver worth the cost effort. Your
opinion is appreciated. Thanks.

 

[Chuck]

On Mon, 19 Apr 2004 19:58:23 -0500, "Mark D. Zacharias"
<mzacharias@yis.us> wrote:

The transistor to which I referred would cut out sound from all sources,
since it is the pass transistor for the relay power supply voltage.

It is a 2SC1438, if memory serves, located near the middle of the regulated
power supply board on the underneath side of the unit.

I can take no responsibility for the use or misuse of this information, and
I hope that only a person of reasonable competence with electronic circuits
will attempt this repair.

Mark Z.

The board no. for this transistor was either Q9 or Q11. For fm
cutting out on this unit, the blue Sanyo electrolytic capacitors on
the tuner board would cause all kinds of intermittent problems. If
you don't have an esr meter, we used to spot them by heating and
cooling each in turn until the culprit showed up. Chuck.