MURPHY V114

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This has given good service, but recently the
60 mA fuse kept blowing and on replacing same with a higher amperage one the U22 EHT rectifier began to disintegrate until the coating was completely stripped l The condenser was suspected and replaced, this
being a large aluminium capacitor, also. the Bakelite high voltage working one -the valve holder
also on the transformer being replaced, another
U22 valve having been fitted this has now repeated the above disintegrating ! I can only
suspect a – possible s/c turns in the winding of
the power transformer ?
However, the fault may be an obscure one and
I would be obliged if you could help me in this
matter with suggestions of a possible checking
through isolating components in turn.
On the last switching on before U22 failure the
sound came on and the EHT gave the usual
timebase lines on tube. -W. R. Prichard
(Welwyn).
We are inclined to suspect the mains transformer as we have met this fault before and
found it to be due to the same cause. Our own method was to check backwards from the tube
by disconnecting the anode cap, then the bleeder
chain. then the smoothing condenser and the valve was still flashing across. In our case the house
fuses blew before the 60 mA fuse in the set.

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