Post by Bob Killip on Feb 28, 2024 19:55:35 GMT 12
I serviced a 1936 63B Pilot radio today that had a B+ dead short. Sadly, the owner had already gone though 2 x 80 rectifiers before calling me; to use a term, they had 'crapped' themselves! Not knowing this, I inserted a spare I had and it immediately lit up like a fireball.
Underside, I spotted a 100 microfarad electro where an 8 microfarad should be, between the 80 valve cathode & before the choke.... what?? Discovered a dead short between here & ground... Ouch!
The 100 electro was acting as a nail. Cut it out & the short disappeared so I installed a 10 cap, re-inserted my 80 valve & the set smiled at me in relief.
The strange thing is, the 100 electro was quite a nice install so wasn't at first obvious... its physical size brought it to my attention.
Owner reckons it had been this way for many years so how did it last so long? He did say the mains transformer had been replaced a long time ago, which is a clue... I suspect the original one objected to the 100 electro.
Picture attached.
Underside, I spotted a 100 microfarad electro where an 8 microfarad should be, between the 80 valve cathode & before the choke.... what?? Discovered a dead short between here & ground... Ouch!
The 100 electro was acting as a nail. Cut it out & the short disappeared so I installed a 10 cap, re-inserted my 80 valve & the set smiled at me in relief.
The strange thing is, the 100 electro was quite a nice install so wasn't at first obvious... its physical size brought it to my attention.
Owner reckons it had been this way for many years so how did it last so long? He did say the mains transformer had been replaced a long time ago, which is a clue... I suspect the original one objected to the 100 electro.
Picture attached.
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