Re: Is it a capacitor, is it a resistor?

Liste des GroupesRevenir à se repair 
Sujet : Re: Is it a capacitor, is it a resistor?
De : legg (at) *nospam* nospam.magma.ca (legg)
Groupes : sci.electronics.repair
Date : 15. Mar 2024, 16:23:18
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <a6m8vi57si3o42atlgu0ij88jhbacv0r06@4ax.com>
References : 1
User-Agent : Forte Agent 4.2/32.1118
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

Date Sujet#  Auteur
14 Mar 24 * Is it a capacitor, is it a resistor?11Liz Tuddenham
14 Mar 24 +* Re: Is it a capacitor, is it a resistor?2jim whitby
14 Mar 24 i`- Re: Is it a capacitor, is it a resistor?1Liz Tuddenham
15 Mar 24 +* Re: Is it a capacitor, is it a resistor?2John Robertson
15 Mar 24 i`- Re: Is it a capacitor, is it a resistor?1Liz Tuddenham
15 Mar 24 +* Re: Is it a capacitor, is it a resistor?2legg
15 Mar 24 i`- Re: Is it a capacitor, is it a resistor?1jim whitby
16 Mar 24 `* Re: Is it a capacitor, is it a resistor?4Chuck
16 Mar 24  `* Re: Is it a capacitor, is it a resistor?3Liz Tuddenham
17 Mar 24   `* Re: Is it a capacitor, is it a resistor?2Cursitor Doom
18 Mar 24    `- Re: Is it a capacitor, is it a resistor?1Chuck

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