[miniman82]

The 5 is a dog HV wise, it was a departure from previous chassis for cost reasons (RCA attempting to stop losing money on each one sold), but it’s shortcomings were quickly reversed with the 7’s and all chassis thereafter. This makes it sort of a ‘one model only’ oddity- all previous chassis had good HV, so did all the ones that came after. I suspect the lack of brightness caused by the weak supply led to customer complaints, which caused them to bump up anode voltage nearly to previous levels in ensuing models.

I’ve tried everything to get move voltage out of my Wingate- I added a HV pot for the shunt tube (didn’t help at all, in fact you can remove the 6BK4 completely and you probably won’t even notice), added a H-drive pot in an attempt to run the horizontal output tube harder (marginal improvement, but still saggy HV on bright scenes), and installed one of those solid state stick rectifiers. Despite all my efforts, I still cannot eclipse 21kv with an image on screen. I still haven’t done the contrast pot mod so that would help a bit, but the main issue is how the FBT is wound.

There is too much primary winding impedance in the coil, which according to ohms law places a hard limit on how much current can pass through it. Meaning that for a given B+ voltage, no matter how hard you drive it you’re only getting so much output from it. Since I cannot alter the primary resistance, the only other variable I’m left with is running more B+ voltage to the circuit to attempt to get more out of it. I may try a dedicated silicon rectifier instead of feeding it from the normal 5U4 tube rectifiers, but I suspect other modifications would be necessary since width tends to grow at the same time.

If I ever get time to do it, I’ll report back.