Capacitor coding help please - UK Vintage Radio Repair and Restoration Discussion Forum

bruce tuckey · 14th Jan 2019, 12:06 pm

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?

ms660 · 14th Jan 2019, 12:13 pm

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

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

Lawrence.

bruce tuckey · 14th Jan 2019, 12:34 pm

Thanks Lawrence. It appears to be a Mullard VA1040.

G8HQP Dave · 14th Jan 2019, 12:45 pm

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?

ms660 · 14th Jan 2019, 12:47 pm

Quote:

Originally Posted by bruce tuckey

Thanks Lawrence. What's a thermistor?

https://en.wikipedia.org/wiki/Thermistor

EDIT: Post crossed.

Lawrence.

Refugee · 14th Jan 2019, 12:57 pm

The thermistor does not look that bad.
I would first make sure that the stylus is OK first.
What tools have you got?

bruce tuckey · 14th Jan 2019, 1:15 pm

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.

Techman · 14th Jan 2019, 1:45 pm

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.

bruce tuckey · 14th Jan 2019, 2:28 pm

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.

14th Jan 2019, 12:06 pm	#1
bruce tuckey Triode Join Date: Nov 2012 Location: Gateshead, Tyne and Wear, UK. Posts: 37	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? Attached Thumbnails

14th Jan 2019, 12:13 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Capacitor coding help please Thermistor, you might find the data on the electrojumble website: http://www.electrojumble.org/techdata.htm Lawrence.

14th Jan 2019, 12:34 pm	#3
bruce tuckey Triode Join Date: Nov 2012 Location: Gateshead, Tyne and Wear, UK. Posts: 37	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.

14th Jan 2019, 12:45 pm	#4
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	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?

14th Jan 2019, 12:57 pm	#6
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	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?

14th Jan 2019, 1:15 pm	#7
bruce tuckey Triode Join Date: Nov 2012 Location: Gateshead, Tyne and Wear, UK. Posts: 37	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.

14th Jan 2019, 1:45 pm	#8
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	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.

14th Jan 2019, 2:28 pm	#9
bruce tuckey Triode Join Date: Nov 2012 Location: Gateshead, Tyne and Wear, UK. Posts: 37	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.