Saturday, 10 May 2014

His Master's Voice 1373

I was going to push on with the dehumidifier wireless controller this weekend, but I've hit an issue. The LCD display I had in stock turns out to be duff, so I'll wait for the others to arrive from China.

In the meantime, a friend bought this in for repair. It's a 1958 HMV Radio. Long and medium wave only, superhet.

Nice maroon cabinet, would suit a West Ham supporter.

PCB in grubby condition. Some evidence of  a burn up by the thermistor.

Took the mains electrolytic capacitor out, and left it on a high voltage, current limited supply overnight to reform. It came up very well. Both 50uF sections measuring 52uF, and both having an ESR of less than an ohm. Not bad for a 56 year old capacitor!  There's a few "Hunts" capacitors that we'll need to change, and an old Plessey electrolytic decoupling the cathode of the output amplifier, so we'll change that as a matter of course.
PCB removed and cleaned up in the sink....

..... Followed by an hour in the oven at 50 deg to dry it out.....
Caps changed, and reassembled.
... and gently on with some power....

The speakers buzzing a little, but we can fix that, and there's a dial lamp out. I've ordered a couple of replacements.

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