Quote:
Originally Posted by irext
I've had noisy carbon resistors cause intermittent grief. They check o/k with a meter but break down when passing current. Since it was the tuner that you disturbed before it came good it might be worth replacing the carbon resistors in it. There shouldn't be many in it but access will be tight. Be careful not to disturb coils and feed through caps etc. The turret will need to be removed to gain access. I'm not a fan of WD40 for electronic work. Use Deoxit as it leaves minimum residue. If you have a spare tuner from another similar vintage set even better. Doesn't have to be physically the same just electrically close enough.
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Wasn't regular WD40 lubricant, it was their
electrical contact cleaner that's just typical electrical contact cleaner with a fancy nozzle. And yeah, I'm very careful around those wire coils that had been hand tuned by carefully forming and pinching in the factory.
I spent some time last night cleaning the tuner contacts and tube pins and so far what I'm seeing is that when all wafer switches are making good contact I'm getting great performance but with the over spec voltages. I tested tube voltages and everything that is fed of the 240V B+ is right about on, and everything fed by the 130V B+ (the one measuring 170V now) is proportionately high. It doesn't seem like it's a bad contact on the tube socket since all voltages are present and no glitching at all if I wiggle the tubes as would normally be associated with dirty connections.
Meanwhile though, the thing is still producing a beautiful picture and sound (though I know at those voltages I'd be cooking tubes alive). This is with CRT pin and high voltages dead-on schematic measurement, so it's not even being pushed out of spec. Not bad for a tube that was found with a brightener (which is of course no longer on) and had virtually no emissions and zero cutoff. That CR70 rejuv zap is incredible!
https://youtu.be/MYtxY-Eanrk
I'll keep cleaning and maybe try replacing some resistors best I can without having to pull the tuner totally apart.
FK