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From: Chuck <chuck23@dejanews.net>
Newsgroups: sci.electronics.repair
Subject: Re: Is it a capacitor, is it a resistor?
Date: Mon, 18 Mar 2024 10:57:20 -0500
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On Sun, 17 Mar 2024 17:52:39 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>On Sat, 16 Mar 2024 20:44:58 +0000, liz@poppyrecords.invalid.invalid
>(Liz Tuddenham) wrote:
>
>>Chuck <chuck23@dejanews.net> wrote:
>>
>>> On Thu, 14 Mar 2024 20:56:32 +0000, liz@poppyrecords.invalid.invalid
>>> (Liz Tuddenham) wrote:
>>> 
>>> >I was asked to repair a Pioneer QX-949 quadraphonic tuner/amplifier.  It
>>> >is a complex beast and one channel had gone down to almost nothing.
>>> >Luckily the service sheet was available and I traced the fault to the
>>> >board which houses the tone controls and filters.
>>> >
>>> >The gain is in two stages with the tone controls around the second
>>> >stage.  On one of the channels, the voltages on the single transistor
>>> >for that stage were all wrong.  After lifting the transistor off the
>>> >board, it became apparent that the base bias was far too high and the
>>> >finger of suspicion pointed to the inter-stage coupling capacitor
>>> >feeding in leakage current from the preceding stage.
>>> >
>>> >I tested the capacitor, which was marked "4.7".  It read exactly 4.7k in
>>> >both directions on an ohm-meter !!!
>>> 
>>> Was it a light blue Sanyo?
>>
>>It was indeed!
>
>Sounds like a known issue, then. Unless Chuck is psychic, of course.
Those Sanyo caps caused many weird problems in Pioneer receivers. Back
in the day, I worked in the main repair department of which is now the
largest electronics retailer in North America. Since  we worked on
only commission, the receiver repairer sometimes got stuck on an odd
problem and didn't want to take a financial hit. I used to love
challenges so I would repair these receivers. I would say, other than
power amp issues, these caps were the main culprits.