RCA 8PCS41 from CL update

[cwmoser]

Originally Posted by Eric H

The Spherical mirror in my set is in very good condition, surprising considering the rest of it.

I'm curious as to what an RCA Spherical Mirror looks like.
Do you have any photos?

Carl

[Eric H]

Originally Posted by cwmoser

I'm curious as to what an RCA Spherical Mirror looks like.
Do you have any photos?

Carl

I don't have a photo at the moment but it pretty much looks just like the one in the Philco, I think it's a bit larger due to the larger CRT.

[Eric H]

Finished recapping the i.f. chassis tonight so I decided to give it a full power up, everything's connected except the Audio Amplifier, that is a separate unit and I don't think it needs to be in place for the set to work.

I put the CRT in a plastic container, must be High Dielectric since it didn't arc through.

First try I got a line on the screen followed after a couple seconds by a shutdown, probably the protection circuit kicking in to prevent a phosphor burn from lack of sweep.
I did a little poking around and didn't see anything obvious, then it occurred to me to check the 5U4's in the power supply (there are three of them!), sure enough one of them was stone cold.
I had been having some trouble with them lighting up before because of bad or dirty sockets, I wiggled it a little and it came on so I gave it the juice again, now I have a full raster!

The focus looks terrible and I have no control of the brightness, it's the same no matter what control I turn, I do get some flashing when I turn the tuner (one channel in particular with the Agile Modulator broadcasting) so I think it's passing a signal all the way to the CRT, I just can't see it because it's washed out, can't hear it either because no amp hooked up.

Anyhow I've had enough X-Rays for tonight, at least it powers up now so I just have to figure out the rest of the issues and finish the cabinet.

[Einar72]

I talked to an old-timer TV tech in Tacoma about these RCA-type sets about 20 years ago. He said his hair fell out after working on one!

[Eric H]

Originally Posted by Einar72

I talked to an old-timer TV tech in Tacoma about these RCA-type sets about 20 years ago. He said his hair fell out after working on one!

LOL, he probably pulled his hair out after working on one of these.
I intend to put the CRT in the barrel before I do any more serious work on it, I just had it on for a couple minutes to see if it would run. I put the lid on the HV cage at least and kept my distance from the CRT.

[Bill Cahill]

These sets have no protection circuits to shut them down.
I suspect that tube socket is shot.RCA used some very cheap sockets.
You could have an hk short in pix. tube. Check your voltages from video amp to brightness control, and, with socket removed, voltages on cathode, and, first grid pins. See if brightness control varies the B+at that pin.
You should see variation.
If the picture tube is bad, the good news is they are fairly common.
Bill Cahill
5TP4

[cwmoser]

Originally Posted by Eric H

LOL, he probably pulled his hair out after working on one of these.
I intend to put the CRT in the barrel before I do any more serious work on it, I just had it on for a couple minutes to see if it would run. I put the lid on the HV cage at least and kept my distance from the CRT.

I'm curious because I have a Philco 48-2500, but where are the
X-rays emitted? From the face of the CRT or all around?

Carl

[earlyfilm]

Originally Posted by Eric H

Anyhow I've had enough X-Rays for tonight, at least it powers up now so I just have to figure out the rest of the issues and finish the cabinet.

Whoa there Eric! There are three ways to avoid radiating yourself.

1) Measure the distance from the top of the light barrel to the center of the mirror and then to the center of the screen in the cabinet. Mount the CRT in the light barrel on a table approximately that distance from your ceiling. If you are sitting very close to the light barrel, I'd suggest adding scrap sheet metal between you had the barrel. Don't forget to ground both the scrap metal and the barrel.

2) Mount the CRT in the light barrel and jury rig a mirror at a right angle to reflect the image off the wall. or operate the light barrel on its side and project directly on the wall. Determine distance by experimentation. Don't forget to put a metal shield on the mirror side of the barrel when operating this way.

3) Disable the voltage trippler. Remove the 2nd and 3rd 8016's and feed the HV directly from the plate cap of the second now-removed 8016, to a standard high voltage 50-53 degree 5 inch test CRT. You will probably have to shim the yoke. The test tube is close enough to the sweep angle of the 5TP4 to not cause a problem, and any X-ray generation will be minimal at this much much lower HV.

James

[Eric H]

Originally Posted by earlyfilm

Whoa there Eric! There are three ways to avoid radiating yourself.

3) Disable the voltage trippler. Remove the 2nd and 3rd 8016's and feed the HV directly from the plate cap of the second now-removed 8016, to a standard high voltage 50-53 degree 5 inch test CRT. You will probably have to shim the yoke. The test tube is close enough to the sweep angle of the 5TP4 to not cause a problem, and any X-ray generation will be minimal at this much much lower HV.

James

This option sounds the best for longer term testing and diagnosis, safer for me and the 5TP4.

I would think it should be fairly safe inside the barrel, it's thick Aluminum and the face of the CRT points downward against a thick, Aluminized mirror.

When I was testing my Philco 48-2500 I pointed the CRT away from me and viewed it in a mirror, later I installed it in the barrel, in any case I avoid being around it as much as possible.

I'm assuming most of the X-rays would be coming out the face of the CRT, the glass is very thin on the face of the 5TP4 and the TP-400 and possibly not Leaded.

Does anyone have any hard facts on the amount of X-rays produced by the 5TP4 operating at 28kv? Guessing the third HV rectifier tube will also be putting out some rays at that voltage?

This set uses three 1B3's by the way, not 8016's, maybe a different version?

[Eric H]

Originally Posted by Bill Cahill

These sets have no protection circuits to shut them down.

If the picture tube is bad, the good news is they are fairly common.
Bill Cahill
5TP4

Bill, the CRT tested good, no shorts, probably something in the circuit.

I thought it had protection because it would operate for a few seconds with a narrow line and then shut down, it did this several times, possibly it just didn't have enough B+ to keep running?

[John Folsom]

The 8016 is just the developmental number for the 1B3. Same thing.

At <= 30KV, the X-Rays produced are relatively soft, and the glass of the mirror and the metal of the barrel are effective in stopping them. And if you keep the covers on the HV cage, likewise. But caution is advised. And distance is a good protector.

[Einar72]

I bought three WWII-dated JAN 8016's on ePay some years back. Anyone know what piece of gear they went in?

[Eric H]

I removed the second 1B3 and hooked a jumper to the output of the first, then I installed a 5AXP4 test CRT, turns out it works very well this way.

I still have no control over the brightness but the "Picture" (Contrast) control does work, possibly the Brightness Pot is bad.
The Sync is all over the place but I was able to get it to hold still long enough to snap the picture below.

Unfortunately as the set gets hot the picture fades out, also I noticed the image is negative, not sure if the 5AXP4 has it's Grid and Cathode wired differently than the 5TP4 or if it's a problem with the chassis.

I haven't tested any of the tubes in the i.f./Vertical sweep chassis but I did swap out most of the relevant ones with no improvement, there are probably some drifted resistors somewhere.

[Eric H]

I wanted to take a look at the brightness issue before I went to bed so I studied the schematic from the brightness control to the CRT and I found a cap I overlooked.

I didn't pay much attention to it because it was the Domino style and I was probably thinking it was a Mica, however the schematic showed it to be a .05@600 and most likely just a common paper cap, why they used this one odd style I don't know, maybe it was supposed to be better quality.

It's cap# 58 on the Sams, between the 6V6 Video Output and the 6AL5 DC Restoration tube, from there it goes to the Grid of the CRT.
As soon as I turned it on I could tell it was better, not only does the video and brightness work now but the sync is fixed too.

I tried it with the 5TP4 also but still with only 10kv on the Anode, the tube works but I can't get any focus with so little HV.

[earlyfilm]

Originally Posted by Eric H

I didn't pay much attention to it because it was the Domino style and I was probably thinking it was a Mica, however the schematic showed it to be a .05@600 and most likely just a common paper cap, why they used this one odd style I don't know, maybe it was supposed to be better quality.

It's cap# 58 on the Sams, between the 6V6 Video Output and the 6AL5 DC Restoration tube, from there it goes to the Grid of the CRT.

Sams capacitors C58 (which goes between the plate of the video output and the grid of the CRT) & C59 (which goes between screen grid of the video output and the cathode of the DC restorer) are called C168 & C171 by RCA and RCA sez:

RCA part # 72996 Capacitor-Moulded paper, .05 mfd., 600 volts (C168, C171)

(Yep! They must have been conservative 'cause they used the old spelling of "molded" )

These RCA projection sets were notorious for blooming issues with high voltage regulation, and I've heard of stories of service men intentionally disabling the DC restoration to lessen focus shift and blooming as the HV drifted when the sets got older. It seems like cutting off your nose to spite your face, but it did allow a failing CRT to remain in service a little longer. Once people started watching TV in more brightly lighted rooms, the DC restorer went the way of the dodo bird as designers no longer saw any benefit.

I suspect the HV issues had more to do with the design of the early 8016's than with DC restoration.

The RCA 630 had a similar circuit, except the 630 used a 6K6 instead of a 6V6 for video output, and it used a normal tubular .05 mfd 600 volt for these two caps.