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Old 14th Jan 2019, 12:06 pm   #1
bruce tuckey
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Default Capacitor coding help please

Morning all and happy new year. My daughter's record player, which only identifies itself as an ALBA solid state, has started to distort a bit during play. A look inside shows a suspect looking disc capacitor, but I'm not familiar with the colour coding. It just appears to be brown with a single orange stripe across. Could someone look at the photos attached and identify it for me please?
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Old 14th Jan 2019, 12:13 pm   #2
ms660
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Default Re: Capacitor coding help please

Thermistor, you might find the data on the electrojumble website:

http://www.electrojumble.org/techdata.htm

Lawrence.
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Old 14th Jan 2019, 12:34 pm   #3
bruce tuckey
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Default Re: Capacitor coding help please

Thanks Lawrence. It appears to be a Mullard VA1040.

Last edited by bruce tuckey; 14th Jan 2019 at 12:57 pm.
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Old 14th Jan 2019, 12:45 pm   #4
G8HQP Dave
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Default Re: Capacitor coding help please

It is a resistor whose resistance varies with temperature. It is probably used to set the bias for the output transistors. If it has become faulty then distortion is quite likely. Why do you suspect that component?
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Old 14th Jan 2019, 12:47 pm   #5
ms660
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Default Re: Capacitor coding help please

Quote:
Originally Posted by bruce tuckey View Post
Thanks Lawrence. What's a thermistor?
https://en.wikipedia.org/wiki/Thermistor

EDIT: Post crossed.

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Old 14th Jan 2019, 12:57 pm   #6
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Default Re: Capacitor coding help please

The thermistor does not look that bad.
I would first make sure that the stylus is OK first.
What tools have you got?
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Old 14th Jan 2019, 1:15 pm   #7
bruce tuckey
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Default Re: Capacitor coding help please

I've cleaned the pots and put a new stylus on. I thought the thermistor looked a bit crusty around the edges, so it might have deteriorated a bit.
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Old 14th Jan 2019, 1:45 pm   #8
Techman
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Default Re: Capacitor coding help please

It sounds like a biasing problem in the output stage or thermal runaway due to leakage in one or both of those output transistors in the copper heatsinks. The adjustment pot on the circuit board should not be adjusted unless you know what you're doing. The pot itself could have a dodgy contact, but any cleaning or replacement would mean careful readjustment with a test meter and service information. There's other possible causes of the distortion that you mention, but saying exactly what it could be is really only guessing, and that's never a good idea if you're a novice.
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Old 14th Jan 2019, 2:28 pm   #9
bruce tuckey
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Default Re: Capacitor coding help please

I meant that I've cleaned the volume and tone pots. I've only worked on valve amps before - usually replacing the capacitors in the can seems to work for them.
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