Quote:
Originally Posted by Alex KL-1
Last year I acquired a delta gun TV, and at testing, I'm desperate due to lack of any image. And a faint image appeared with bias pots maxed out. I think the CRT was dead. But then I noted that the G2 bias caps are paper-in-oil, and I decided then to change it for polypropilene caps. Voilą! Image back, with great brightness, at middle of adjusment!
The bias normally have relatively high DC resistance, so bad caps can upset correct adjustment.
If you not checked yet, is good to check if cathode, G1 or G2 have messed DC voltages due to leaky caps or drifted resistors. Also serves for various other faults you have found or will encounter. Unfortunately, older sets are not so reliable like 80's+ sets...
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I noticed that there were a relatively large number of paper oil caps in this tv as they are many of these older sets from the early 1970s and earlies. I definitely am going to end up eventually recapping all the electrolytics, any remaining wax papers I may have overlooked and the paper oil ones too.
Even if the ESR has not went bad yet, they can still be leaky as I have learned is often the case when at operating voltages.