Dumont RA-110 from ETF

[Kamakiri]

Oh, I'm keeping it, believe me

Might have one lined up, but if not I'll definitely let you know

[Bill Cahill]

The disc caps were originally paper capacitors. May not run as well. They are in critical circuits, and, may cause problems.
The solenoid powers on B+ when set is nearly warmed up so it won't surge as badly, which, surges can damage parts, and, Dumont knew that. By the way, Most early Crosleys were made by Dumont, or, RCA.
Bill Cahill

[Kamakiri]

So I'm in the final stages of restoration now!

Okay, to be fair, it was mostly restored already. Anywho.....

I have one filter cap to do. It's a double 70 uF @ 175V. Weird thing is that there are no polarities marked on the cap, 4 wires, two of which go to ground.

I would normally assume the negative leads are chassis ground, and the positives go to wherever they go, because it's not labeled as a bias cap in the Sams. But, on the chassis ground side of the caps, it almost looks like a "+" scrawled into the solder. I've never seen a filter cap with NO polarity markings on it whatsoever, and 4 wires coming out of the cap, two on each end.

That said...what way does the replacement go in?

[Phil Nelson]

If I am looking at the correct schematic (Sams 93-4, covers RA-103D/RA-104A/RA-110A), it shows that the positive leads of both 70-mfd caps (C9A and C9B) go to ground. The negative leads go on each side of a choke-resistor combination (L2 and R135).

Phil Nelson

[old_coot88]

Originally Posted by Kamakiri

...I've never seen a filter cap with NO polarity markings on it whatsoever, and 4 wires coming out of the cap, two on each end.

I've seen double ended, cardboard-sleeved filter caps before. 'Cept the leads coming out each end were red & black, clearly indicating polarity.
They were used in Sears 17" portables, in the doubler circuit with seleniums.
The first time I ever replaced one, I (mistakenly) thought the red lead coming out one end went with the black lead coming out the other end, and proceeded to wire it accordingly. The dang set came on and worked, but with humungous hum bars and hourglassing.
I quickly corrected the goof.

[Kamakiri]

Here's a pic of the one end of the cap. I shouldn't say that it's *not* marked for polarity, because it clearly *is*, but it's not so clear. I had to take this picture 5 times and then enhance it to try to get it so that you could see. There's just a "+" carved in the solder, and it's so light that it's hard to tell it's even there. It's not even really visible on the other end of the cap. Other than the values stamped into the side of the cap, it's otherwise unmarked.

Second pic is the new caps installed where the old one was.

[kramden66]

i have one , started to recap the chassis and got side tracked on other sets , i hope to finish it soon and see what the end result is
the crt was very weak , i got one from another vk member and put it in , the original one i was going to put on the side in the hopes to rejuvenate or rebuild if there is ever a rebuild place again one day anyway the socket came loose and off and as i was carrying it it slipped , my thumb hit the glass nipple , a nice air in rush sound occurred and that was the end of that

[Kamakiri]

Thanks for double checking me. It confused me because I was under the assumption that only bias caps have a positive ground, and these weren't labeled as bias caps. Right about here is where the gaps in my knowledge become chasms....

[Phil Nelson]

That's a weird looking electrolytic. I don't recall seeing one with a pair of leads at both ends like that.

Phil Nelson

[Bill Cahill]

Sure it's not on the yoke circuit? Or, just a weird bias?
The can likely isn't part of the electrical circuitry.
Trace your wires.
Bill Cahill

[Kamakiri]

Originally Posted by Bill Cahill

The can likely isn't part of the electrical circuitry

Splain.

[Bill Cahill]

Simple.. Electircally, the two capacitors are not connected to the can.
What colors are the wires? Where do they connect?
Bill Cahill

[Kamakiri]

Connected to what can? The two capacitors ARE that yellow cap, one on each end believe it or not. Picture sawing it in half and each half being a stand alone filter cap. Weird as it is, that's what it seems to be.

The thing it's encased in is a U-channel that sticks up on the chassis and holds two 6X4 tubes horizontally. Super weird design for sure.

[Kamakiri]

Weird how it's just rolled up on the left...

https://www.youtube.com/watch?v=OELi...ature=youtu.be

[wiseguy]

did you replace all of the paper caps yet?
there are a few in the Horiz Sweep area that when bad/leaking will cause this, and also a weak damper tube 5v4 would cause this, if the Horiz drive is turned up too high will cause this also
I would start first making sure all the caps in the Horiz osc/output/flyback are new, there is a resistor r122 and r120 that will change value, check those
But the Capacitors c101,102,103,106,105,107 is very important