Resistor or jumper at hv rectifer socket: Zenith 25mc30

[Tubejunke]

Originally Posted by Tubejunke

OK, I just figured out that I have been using Sams Set 722, Folder 4 which is for the 25LC30/U! Geez! It only specifies pins 1 &12 as heater connections. I need to get a .pdf on my 25MC30 somewhere. H

For the sake of this thread's information being accurate I must correct what is quoted above. My set's chassis is indeed a 25LC30 and the model is 5111. I don't even know where I came up with 25MC30 being what mine is. I am guessing that the L & M identifiers must have to do with production year. Mine should be the 1964 and the MCs should be 1965 and the last of that style plain metal cabinet round crt TV production.

Thinking I had the wrong schematic, I ended up finding a .pdf Sam's folder on the 25MC30 and was happy. Looking over the horizontal output and HV sections of the schematic I noticed that the 6JS6 horizontal output tube was used. I knew that my set employed the 6HF5 sweep tube. That led me to look at all the models covered for that year 1965 on the first page. I saw that the models were all different and mine 5111 was not there. I think instead there is a 5211 which is probably that year's equivalent. From there I opened my original file for the 25LC30 and saw my model and the right 6HF5 sweep circuit

In a way I wish that my mistake was correct as I have heard that the 6JS6 H Output tube was a better tube by design (plus I have a few in my useless compactron box). I don't think that they are subs for one another, so I won't even worry about that. The 6HF5 seems to do as well as any. I'm not sure how many other changes that there were in that one year. Most everything I glanced at looked the same. I notice Zenith regularly made small changes such as one or two tubes from year to year. That's the world of engineering for better or worse. I wonder how much better the 6JS6 really is just out of curiosity.

Anyway, I think the confusion on my part started with all the talk about the HV rectifier pin #s shown on my LC schematic. They appear to be wrong as pins 1 and 12 are shown to apparently be the heater terminals. Well, they are and they aren't, but you have to have the tube data to see what is going on internally with the 3AT2. Many pins are duplicate or NC. The MC schematic shows the same thing and it thew me off because I expected my set to be wired like the schematic as I would think a factory would adhere to; evidently not so.

If anyone here needs a good copy of the 25MC30, I now have it and would be glad to share it with anyone. Just let me know....