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Old 16th Oct 2019, 3:09 pm   #24
julie_m
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Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: Westminster S470M power supply problem?

The only valve that could pass enough current to pull down the supply voltage is the UCL82. If the 47nF capacitor to pin 3 has been replaced with a new, modern one, then the valve could be faulty. I would have thought a valve fault unlikely, but once you have eliminated the impossible .....

Try another UCL82; but before you go ordering one, try a new grid capacitor, just in case the new one you've put in is faulty. It's also not altogether unheard-of for valve holders to go faulty and become conductive, especially if they have been overheated in the past.
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