Quote:
Originally Posted by zeno
That looks like a bad HV reg pot. Width would come in a little.
Give it a little bump & it would snap in. Try cleaning the crap out of it & adjusting it. BTW on schematic it shows 2 versions of HV reg
circuit ( dotted lines ) see what I mean ? No 2 alike !
Tripler is made by GE & marked with Zenith part ##. Date code
is 72-48. = 48 th week of 1972. Set was born with it 99%.
73 Zeno 
LFOD ! |
I took your suggestion and cleaned that HV pot, and the headroom for HV has improved, but any adjustment above 18KV produces excessive cathode current on the HO. If the HV is adjusted to around 20kv, the K current skyrockets to around 330mA, which is probably no bueno for the flyback and does produce some red-plating. The current seems poorly regulated and jumps around a little too.
For this reason, because of poor regulation I'm suspecting bad VDRs. I have new KOA SPEERS MOV's I can swap in there, but have no idea if they would work, and I have absolutely no info on the VDRs that are in there, other than a black /orange color code.
One thing I just noticed is that the Hor freq control is cranked all the way to one end of the range to maintain hold. When I start the set up the H hold is missing for a few seconds. This lack of range may be indicator of a cause of insufficient drive as well