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Old 22nd Feb 2019, 3:48 pm   #1
chriswood1900
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Default Cossor 54. What is the HT voltage?

A few months ago I made a start on fixing the mains transformer in my Cossor 54 that I bought at RWB last year, this was the one restored by Brian Cluff shown here:-

https://www.radios-tv.co.uk/communit...c-tv-re-birth/

It had developed a shorted turn. Mike Barker did a great rewind for me and I set about refitting it last weekend. It went in very easily, Mike had used the same colour code and I simply re-soldered the wires back on to their respective tags. On powering up slowly via a variac so as not to stress the components and filaments I was rewarded with a raster and a slightly out of line test card, a few adjustments to the hold controls improved things and I left it alone as the actual shift controls seem very crude using the changing of fixed value resistors and the magnets in the cabinet.

It ran happily for 30mins this time with no overheating of the transformer, previously it was to hot to touch and oozing wax after 10mins

One thing I am unsure of which others with experience of this set might be able to answer is what is the correct HT voltage? On my set it is around 275V but on some circuits I have seen it has been handwritten in as 350V, before I go looking for a fault I wanted to know what it should be. It could of course be a weak rectifier valve.

Pictures show the chassis and a picture via an Aurora.

Chris
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Old 22nd Feb 2019, 5:10 pm   #2
FERNSEH
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Default Re: Cossor 54 what is the HT voltage

Hi Chris, checked the HT voltage on the 431U rectifier in my Cossor 54 and it is 260V.
On the sound output transformer primary the readings are 204V and 150V.
The receiver HT supply doesn't need to be high because the HT for the timebases is supplied from the 3kV EHT.

DFWB.
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Old 22nd Feb 2019, 5:35 pm   #3
chriswood1900
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Default Re: Cossor 54 what is the HT voltage

Thanks DFWB.

It looks that mine is about right then, I thought I would check it for future reference after fitting the transformer, but was confused by seeing various voltages written on old drawings.

Regards, Chris.
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