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 Post subject: Pioneer SX-850 puzzling problem.
PostPosted: Jan Wed 16, 2019 8:25 pm 
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Joined: Mar Tue 03, 2009 11:12 pm
Posts: 1534
Location: Hutchinson KS
This thing is making my gray hair even more gray. Set works fine until you operate the tone switches and then it blows the right channel output stage. If someone can post the schematic of the tone amplifier assembly schematic would be very helpful. I tried for two hours to attach the page 72 of the service manual or page 55 of HiFi Engine website page to no avail. This circuit has one transistor (per channel) on tis board, with 36 volts B+ and B- neg chassis ground supplying the circuit. Pin 7 of the circuit has a varying + DC voltage of .8 volts. But when the 36 volts is removed this voltage swings to the negative side with 2 volts or so, then dies away. I have all leads disconnected, supplying an external 36 volts. Where is the negative voltage coming from? I am currently chasing down a leakage path of why there is a small positive dc volts, the tantalum caps are leaky!


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 Post subject: Re: Pioneer SX-850 puzzling problem.
PostPosted: Jan Wed 16, 2019 8:54 pm 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 4703
Location: Norfolk, VA
I just downloaded the HIfi Engine manual, so still checking, but looks complete.

Attachment:
AWG039.gif
AWG039.gif [ 67.2 KiB | Viewed 491 times ]

_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Pioneer SX-850 puzzling problem.
PostPosted: Jan Wed 16, 2019 9:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 18545
Location: Albuquerque, NM 87123
Just replace all the electrolytics.


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 Post subject: Re: Pioneer SX-850 puzzling problem.
PostPosted: Jan Wed 16, 2019 10:22 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10095
Location: Toledo, Ohio
Johnnysan wrote:
Just replace all the electrolytics.


And tantalums, if any.

_________________
Jim
KE8GMW
------------------------
"AC volts and DC volts and little lamps and lities..."


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