I bought a old B&W set today. It has wood doors that hide the picture tube and knobs kinda cool. I'll post a pic when I get it home.

I just wondered how old it might be and what sams would apply to it.

I found these numbers on the chassis:

274-113 5

RVC-L9

The picture tube is a 17CP4 was that a common tube?

Any help would be appreciated.

Thanks

Look for a KCS number on the chassis or a model number on the back cover.

From the CRT type I would guess early 1950's 51-52 perhaps.

The cover was missing, but the guy found it today.

Model is a 7-T-123

Some pictures....

Sams 134-9. Note that there is a 7-T-123B that is covered in 156-11.

I have extra copies of these. If you want one send me a PM with your address. I try to get $5 for them.

Definitely a good restoration candidate.

I have a spare good 17CP4 if you need it.

Thanks guys, I'll pull the chassis today and see what else it might need. Where is the best place to buy electrolytic capacitors?

If you need a simple solution for capacitors without having to rummage through catalogs justradios.com is an excellent place for capacitors. Tubesandmore.com (antique electronics suply) is also a good place.

I made some progress today. Took the chassis out and cleaned it checked that the electrolytic weren't shorted. I took a chance and plugged it in and got about 2-3 inches of vertical deflection. It looked like the raster was only deflected from the center up..not balanced around the center of the screen.....
any ideas???

Thanks

The wax/paper caps are leaking .
It will improve , or work perfect once they are changed .
If you need scans of the schematics let me know and I'll email them to you .
I think my data covers that set ?

I got the schematic today and ordered some capacitors from justradios.com for the vertical section.

I would replace the rest of the paper capacitors while you're at it.

Phil Nelson

I have almost full vertical deflection after changing some caps, but the set has a slight arcing sound which causes the raster to jump around. changing the width control makes the noise increase and decrease. Also, the width control really affects the brightness. Any suggestions for cleaning the high voltage areas?

Thanks

Your arcing may be caused by a defective doorknob capacitor in the high voltage cage.

Also check the high voltage lead going to the rim of the picture tube for cracks in the insulation.

The width control effects the brightness and arcing because its adjusting the screen voltage to the horizontal amplifier tube. Lower the voltage on the screen and you get a slightly dimmer, thinner picture with less high voltage.

I STRONGLY recommend you replace all of the paper and electrolytic capacitors. You need to be sure the electronics are up to snuff before you do any serious troubleshooting of the HV and sweep sections.

I ordered about $50 worth of caps today...should be a good start.

Installed the first batch of caps...have to order more. One of the plastic covered paper "line to chassis" caps was split open. I heard the set of pop once before I started recapping, so that might of been it. It's amazing how much smaller the modern electrolytic capacitors are compared to the metal cans. Same goes for paper vs. polyester film.

...amazing how much smaller the modern electrolytic capacitors are... They sure are - more room for ventilation!

That's the main reason I don't bother re-stuffing very often. I just leave the old cans in place and stick the new ones underneath. I've been criticized for that (mainly by radio restorers) :rolleyes:

Either way, we're preserving history :)

Progress is slow....I still have the arcing sound and reduced vertical and horizontal sweep. I can't see any arcing in a dark room, but I can hear it and see the raster flicker. I'm suspicious of the 600pf 30KV cap from the HV lead to ground. Has anyone seen one of these caps give problems (arcing)? It snaps into clips and has 1/8" diameter axial leads. It doesn't arc when the cap is removed.

Also, I felt a tingle when I touched the chassis and measured 70VAC from chassis to ground..any possible cause other than leakage from the power transformer?

Progress is slow....I still have the arcing sound and reduced vertical and horizontal sweep. I can't any arcing in a dark room but I can hear it and see the raster flicker. I'm suspicious of the 600pf 30KV cap from the high lead to ground. Has anyone seen one of these caps give problems (arcing)? It snaps into clips and has 1/8" diameter axial leads. It doesn't arc when the cap is removed.

Also, I felt a tingle when I touched the chassis and measured 70VAC from chassis to ground..any possible cause other than leakage from the power transformer?

The line to chassis caps will do that also. You said you replaced them. What value did they have in it? You should also use a safety cap for the the line to chassis cap. JustRadios has an explanation on their site about which types to use.

Assuming it's a direct leak from a 120VAC line and that you measured it with a 10meg input impedance voltmeter then you have about 5 microamps of leakage current. Most GFCIs are set to trip at 5 milliamps. I think you're pretty safe and that what you're measuring is due to the line to chassis capacitor. Just make certain that it's the correct type of safety capacitor.

John

Progress is slow....I still have the arcing sound and reduced vertical and horizontal sweep. I can't any arcing in a dark room but I can hear it and see the raster flicker. I'm suspicious of the 600pf 30KV cap from the high lead to ground. Has anyone seen one of these caps give problems (arcing)? It snaps into clips and has 1/8" diameter axial leads. It doesn't arc when the cap is removed.


Yes those "doorknob" caps can arc internally.

I found a bad one just last week, it made a constant crackling sound but I couldn't see anything arcing, I found it by subbing it with another.

It probably won't cause the reduced sweep.

Does this set have two 1B3 rectifiers in a doubler circuit?

Where can you find "doorknob" caps at?

It has a single 1B3. What is the best way to test the cap? Apply HV to it from another TV and see if it arcs? I used new safety caps from justradios

Where can you find "doorknob" caps at?

Surplussales, ebay, rfparts...

John

It has a single 1B3. What is the best way to test the cap? Apply HV to it from another TV and see if it arcs? I used new safety caps from justradios

It sounds like yours is arcing internally so the only indication that it's arcing, if you tried it on another set, would be it pulling the HV low on that set. I guess you'd hear the arcing.

John

I found a doorknob cap one ebay, but It's coming from China so it might take awhile to get here. The cap in the TV is 600pf on the Sams the value is 500pf. The one I ordered is 500pf.

I found a doorknob cap one ebay, but It's coming from China so it might take awhile to get here. The cap in the TV is 600pf on the Sams the value is 500pf. The one I ordered is 500pf.


Won't matter much you probably don't even need it if the CRT is Dag coated. It's just the HV filter.

I tried the set without the HV cap and it seems to work fine with out it...no more sizzling


I replaced the Vert & Horiz. tubes along with some more caps and the cathode resistor on the horiz. tube. It measured 150 ohm instead of 100. I got a full raster for about 2 hours then the width shrank about an inch on each side.


The raster had a black bar in the center like hum on the video. It went away when I pulled the RF amp. from the tuner. The SAMs shows a 6CB6 as the rf amp, but the TV had a 6AG5 instead. Are they interchangeable?..any idea which one is correct?

Thanks

I tried the set without the HV cap and it seems to work fine with out it...no more sizzling


I replaced the Vert & Horiz. tubes along with some more caps and the cathode resistor on the horiz. tube. It measured 150 ohm instead of 100. I got a full raster for about 2 hours then the width shrank about an inch on each side.


The raster had a black bar in the center like hum on the video. It went away when I pulled the RF amp. from the tuner. The SAMs shows a 6CB6 as the rf amp, but the TV had a 6AG5 instead. Are they interchangeable?..any idea which one is correct?

Thanks

They're similar, but not exactly the same. The 6AG5 has the supressor grid connected internally to the cathode. The 6CB6 doesn't. Does the Sams show pin 7 & 2 connected?

Is there a tube chart on the set?

John

No tube chart, but the sams shows a 6CB6 symbol without the internal connection. I have a 6CB6 coming from ebay.