Resistor or jumper at hv rectifer socket: Zenith 25mc30

[Tubejunke]

Thanks everyone, and special thanks to Dave with the pages posted. This turned out to be a great thread that I think will be an excellent source in the future for others. I think I am far from the first to be hunting a corona or arching issue which just can't be seen; even in the dark.

As I have said before; I don't know if I would ever have found this if the damage from the arching hadn't burned my rectifier socket causing a pin to pull with the tube and leading me into further investigation.

[Zenith6S321]

Originally Posted by Tubejunke

Thanks everyone, and special thanks to Dave with the pages posted. This turned out to be a great thread that I think will be an excellent source in the future for others. I think I am far from the first to be hunting a corona or arching issue which just can't be seen; even in the dark.

As I have said before; I don't know if I would ever have found this if the damage from the arching hadn't burned my rectifier socket causing a pin to pull with the tube and leading me into further investigation.

Hope the information helps. Its just guesses until you try it and find the cause. Please let us know how it turns out.

Dave

[Tubejunke]

Originally Posted by Zenith6S321

Hope the information helps. Its just guesses until you try it and find the cause. Please let us know how it turns out.

Dave

I am certain now of exactly what to do as far as proceeding with the repair of the burned socket which was without question. In my search for a replacement socket I was finding that some sets had the resistor and others (newer) didn't. I needed more information as my inclination was not to eliminate or alter something that was at least in my set. Now I can proceed with certainty and the information given is beyond helpful.

I still can't help but wonder how I had HV with the resistor burned in two. My only guess is that it was arching across the two burned open ends of the resistor. The burned out socket (pins 4 and 5) as well as same tube pins badly corroded may be further evidence backing this theory. Heck, pin 4 is a blank! Beyond a shadow of a doubt the resistor didn't burn any of the last number of times the set was in use.

Beyond the resistor topic my immediate concern will be that of HO cathode current being high at line potential. I doubt that this repair will correct that, but all of this is a learning process for me. Perhaps the issues mentioned and soon to be corrected do play a hand in that. I will know as soon as the socket arrives (hopefully later today). Lots of snow here for this part of the country which makes for a perfect day to work on electronics projects.

[NewVista]

Originally Posted by Tubejunke

my immediate concern will be that of HO cathode current being high at line potential. .

I'm worried about that also given the melted wax on my 25LC . Perhaps a small cathode resistor could be added to Horiz Out and its voltage drop could be used as tuning indicator to optimize the Horiz Efficiency Coil? It would also reduce H.O.T. primary current.

I see the 25LC schematic AC input is designated 120v - within spec of modern utility voltage.

Was looking for "troublesome" degaussing thermistor and found the 25LC20's have no automatic degaussing coil