RCA 8PCS41 from CL update

[cwmoser]

Its already looking great. The grain patterns in the wood work is
something you just don't see in any furniture today.

Carl

[cwmoser]

Hey John, didn't you restore a Philco 48-2500 projection TV?
How much of an improvement did a resilvered spherical mirror
make over your old mirror? I ask this because the spherical
mirror in my 48-2500 is not perfect but it looks pretty good.
Mine does though have some places in it that you can see straight
through though.

Carl

[John Folsom]

My mirror in my 48-2500 was in very poor condition, so having it resurfaced made all the difference. However, dummy that I can be, I attempted to clean the curved mirror in the lid. Disaster! The top coat on that mirror is a multi-coat lacquer coat filled with micro-spheres which act to provide optical gain.

But I have restored several RCA projection sets from the late 1940s, and if you want to achieve optimum optical resolution, resilvering the spherical mirror and replacing the flat front surface mirror is the way to go. These sets can provide quite acceptable bright (though very directional) images when operating at peak performance. Of course, of "close is good enough", then the mirrors you have may be tood enough.

[Eric H]

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

[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.

[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?

[earlyfilm]

Originally Posted by Eric H

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

My 1949 made 8PCS41 cabinet sticker calls for the 8016.

Between it and the other 1949 9PC41 I had one 8016 (probable replacment) and two RCA branded 1B3/8016. The rest were replacment 1B3.

Originally Posted by John Folsom

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

Usually interchangable, but:

8016 = PIV 10,000 max, Ip = 7,6 max ma, average 2 max ma (1942 data)
1B3/8016 = PIV 30,00 max, Ip = 17 max ma, average 2 max ma (1949 data)
1G3/1B3 = PIV 33,000 max, Ip = 35 max ma, average 1.1 max ma (1965 data)

As the tubes improved the PIV increased, the short-flow current increased, but the average-flow current decreased. I would not put a 1G3 in an RCA projection set.

James

[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

[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?

[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