Re: Murphy A188C repair.
Sounds like a high resistance connection somewhere between the 4V winding on the transformer and the valve socket. With the valve removed, your meter draws a very small current so the high resistance connection doesn't drop much voltage, you measure the 4V. With the valve in place, the current drawn by the filament causes a voltage drop across te bad connection.
With the UU6 removed and the radio unplugged from the mains what resistance do you measure between pins 1 and 8 of the UU6's socket?
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