Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: legg Newsgroups: sci.electronics.repair Subject: Re: Is it a capacitor, is it a resistor? Date: Fri, 15 Mar 2024 10:23:18 -0400 Organization: A noiseless patient Spider Lines: 26 Message-ID: References: <1qqfgdv.1y9tmdayl1lntN%liz@poppyrecords.invalid.invalid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Info: dont-email.me; posting-host="f51f38375e6d745b9972aa535c2cd64f"; logging-data="2441869"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19DG1jNTMRsKuMerMzVMfpB" Cancel-Lock: sha1:3vb0OqT6o5/3HcEWhtca8ddofN0= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 2073 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 !!! Used to keep a special box for spectacularly wrong parts, but never found a situation where their re-use was justified, even as a joke. Everybody takes themselves so seriously these days. At least each part had a story behind it . . . . RL