Hello..my first TV

[JohnCT]

Is that ceramic across the line? If so, you should replace that with an "X" type capacitor.

But I remember back in the 60s when RCA had a recall because they had brown plastic caps right across the AC line that would fail and spew carbon and metal bits like a blowtorch. The cap RCA supplied looked like that ceramic, and I never saw one fail, but X and Y caps are now used for this purpose.

John

[Donj]

No, the photo shows part of the vert sweep circuitry, only a few of 5 ceramic bodied caps under the hood. I already put safety caps across the line.
Do you think I should be safe leaving the ceramic bodied caps there? They are not original, as the parts list specifies paper/wax where they are.

[JohnCT]

Originally Posted by Donj

No, the photo shows part of the vert sweep circuitry, only a few of 5 ceramic bodied caps under the hood. I already put safety caps across the line.
Do you think I should be safe leaving the ceramic bodied caps there? They are not original, as the parts list specifies paper/wax where they are.

Unless someone else has info that I don't know about, I'd leave the ceramic body caps in there assuming they're the same value (or really close) and equal to or higher than the original voltage ratings.

John

[Electronic M]

Originally Posted by Donj

No, the photo shows part of the vert sweep circuitry, only a few of 5 ceramic bodied caps under the hood. I already put safety caps across the line.
Do you think I should be safe leaving the ceramic bodied caps there? They are not original, as the parts list specifies paper/wax where they are.

Flat ceramic disc caps are usually best to leave unless tested defective, BUT tubular ceramic bodied caps (as the last picture on the last page shows) should always be changed.
Disc ceramics use ceramic dielectric and rarely fail. Tubular ceramic caps usually are paper dielectric and are VERY high failure. Paper dielectric capacitors are not just paper/cardboard tubes they were sold in plastic shells (I see some in your pictures too), ceramic shells and metal shells....No matter the shell material paper dielectric capacitors are BAD and should be changed.

The plastic shell caps and ceramic shell paper caps are known to explode when they overheat.

[Donj]

I can't express how much I appreciate the guidance you folks have been sending my way. Makes this task a learning experience..
So the recap continues along with checking resistor values. Have only found 1 resistor that hasn't measured almost right on as have all the others. Most have been within 3% of marked values. The one bad one was marked 10k and measured 251k.

Next question regards a selenium rectifier within the filament string. I have yet to test it and am just wondering if I should just replace it since I'm in there.
Would a couple of 1N4007s do the trick? Part sheet just describes "selenium rectifier" nothing further. What purpose does this serve?

[old_coot88]

V2, whatever tube that is, gets filtered positive DC on its heater, supplied by that circiut. The little selenuim is a full-wave rectifier. If replacing with Si diodes, you may need to bump the value of that 1 ohm resistor up a bit to avoid overvolting V2's heater.

[jr_tech]

Scratching my head here... why is V2 heater also connected to the upper leg of the AC heater supply?

What is V2 and what is its function?

jr

[Donj]

Coot,
V2 is the oscillator tube on the tuner... pretty sensitive area to be messing with if not necessary I expect. Maybe I best leave it be for now.

[Donj]

jr,
Tube is a 12at7. Split filament maybe?

[JohnCT]

Originally Posted by Electronic M

Tubular ceramic caps usually are paper dielectric and are VERY high failure. Paper dielectric capacitors are not just paper/cardboard tubes they were sold in plastic shells (I see some in your pictures too), ceramic shells and metal shells....No matter the shell material paper dielectric capacitors are BAD and should be changed.

This made me wonder as I had never seen a ceramic tubular fail, but then, my experience has been limited from 70s TVs until present.

I took this cap from my old TV stock:



...and cracked it open. What I found was that this capacitor is a foil and plastic film, not paper. This cap would have been factory installed from the 60s to the 80s in a transistor TV, so perhaps paper ceramic caps were gone by then.



But what the heck, caps are cheap enough and cheap insurance. Change all tubulars seems to be good advice on tube TVs. I suspect any ceramics in later transistor TVs are fine.

John