Dumont RA-110 from ETF

[Kamakiri]

Originally Posted by jr_tech

Sorry to hear, that is typical heater burn-out for a very gassy tube... likely the 19AP4 was pretty much "up to air" when you got it. How do the getters look?

jr

I didn't notice anything out of the ordinary or remarkable....they weren't white. But then again when I heard the SNAP and the filament went dead....well.....that was about that.

Set's still in the garage at the moment. I hafta take 3 doors and one long stairwell railing to get it in the house

[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

[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

[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.

[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.

[Kamakiri]

Chassis is in the cabinet and I'm just a 5V4 away from first power up. Ordered one up on ebay

Swapped the 19AP4 out of the Emerson I just got. I got a tip to lay the cabinet down on its face to install the tube, and that is dead on. Any other way risks breaking the picture tube.

The anode is securely on, but on the other side is this ground strap. Where on the chassis should this be making contact?

[wiseguy]

on my 109A set and another its position is down and the lower bend part or "J" should touch the chassis when you slide the chassis forward, it does not screw to the chassis but just touches it to ground, it looks like it is on backwards so you will need to flip it over and down