1949 9PC41 projection set
 

I'm considering restoring my 1949 RCA projection set this winter after the GE 810. Has anyone restored one of these lately? My conical mirror and picture tube are in good condition. Anything I need to know or look for?

The high voltage chassis has a tripler. Make sure that you thoroughly clean the high voltage area to ensure no arc-over. Also, the 5TP4 runs at 26-27KV, so it can produce x-rays. Run it with the tube inside the bucket.

I see from your picture that you have the remote. Very nice. I was able to recently score a correct remote for mine.

I picked up one of these monsters 20 years ago from a collector who had passed away. It was never sold and is brand new on the pallet. Knobs and paper work are not installed ans stapled in a sealed bag in the cabinet. The tubes have cardboard protectors over them and the remote and the yoke are also in sealed RCA boxes. It must of been all set up by the service tech when delivered.

Steve Pielock restored one of these or a similar set a couple of years ago or so, and had some good descriptions either here or on the Antique Radio Forum. It would be worthwhile to find his discussions. His forum name is "pielock" if I remember right.

I've restored the chassis of one but still working on the cabinet.

It's basically the same as any TV except I'll echo what Hi_Volt said, clean the HV section immaculately or it will arc and sizzle, and of course the X-Ray danger and the 27,000 volts is nothing to get careless with.

While i was working on mine I disabled the Tripler and just ran it off the first HV rectifier tube with a normal 5AXP4 test CRT, that way you aren't exposed to X-Rays or major HV while poking around.

Thought I'd share a picture of the horizontal deflection chassis.

IIRC these sets have HV regulation issues which most objectionably manifests it's self as focus change with scene content.....One member found a solution which was to disable the tube tripler and use a SS tripler from a 70's set.

Interesting concept. I'd like to see details on that.

Here's Eric's restore thread where Tom Albrecht and TV Engineer chime in on the HV sage/focus issues. At the end of this thread Tom posts a link to another thread where he made additional tweaks to his set. In the end it's a very impressive performer.

http://www.videokarma.org/showthread.php?t=248752

Very cool set with the original remote. I know an old-time repairman who'll work on any vintage TV's except the projection sets. I would imagine they're a bit more involved than typical TV's.

Oh just put 110 or so 1N5388s in series across the CRT and be done with it. LEave the DC restorer in. 1N5388s are cheap.

Here is a picture of the bottom of the horizontal deflection chassis. I'll start recapping with capacitors I have on hand.

It didn't post the picture on my last comment. So far there's not nearly as many caps as I thought there would be. I like that there are multiple chassis. Makes it more manageable and less overwhelming. I ordered the remaining caps for my GE 810 and I'll probably get into this set after Christmas. I'll begin replacing parts with what I have and begin cleaning and testing all of tubes. I'm looking forward to getting this big screen lit up! I have the original RCA device data, thanks to a fellow collector.

Look at the size of the transformers used on this low voltage power supply! This set uses 41 tubes whereas the philco projection set of this era only used I think around 25. Why such a difference?

RCA and Dumont in the early post-war were trying to show off what TV could do so they tended to over engineer their chassis. It was not going to market if it had JUST enough to work properly, it had to have as much stability and performance as it could. RCA also was allergic to stuff the did not hold the patent to like the tube count reducing inter-carrier audio (IIRC they were the last to adopt it).

Look at a 630 chassis 10" table set....About 40 tubes in those too.

These three chassis should keep me busy awhile. It looks like the vertical section on the if/rf chassis has had some repairs before. Several bumblebee replacements and one electrolytic can has a lot of leakage underneath it too. The if/rf chassis has a few 1000v caps I'll have to order too.

This set has an oddball value wax cap in the vertical section. It's a .06 at 1600v. Can I put a .05 and .01 in a series and be alright? They're both 1600v.

Hi, Not in series, but across each other. You want the value to add not divide. All the best, Tom

Ok so in parallel, got it thanks!

To be more precise in parallel is the way you want to connect the two caps, NOT in series.

Capacitors in parallel add. Capacitors in series take on a value less than the smallest one in the string.....It is the other way around for resistors in series, but the formulas are the same IIRC.

After replacing 22 electrolytics and all paper caps, excluding 1000v ones, I am getting close to a first power up on a variac! Just waiting on the 1000v caps to come in the mail any day now....I also replaced any out of tolerance resistors and any ones that looked questionable.

Looking good.

Well first power up was a disappointment, with nothing happening. Not a single tube lit up. Back to the drawing board...

Anyone got any ideas? The fuse in the power supply chassis is good and I've checked multiple times to make sure I've hooked all of the cables back up correctly. I'm going to do a continuity check on the on/off switch to make its not defective. I haven't seen a simple switch like that go open before, but I can't imagine why nothing is lighting up?

Start as close as you can to the AC plug and work your way back until you find where the voltage drops off?
If you aren't even getting the tubes lighting it's going to be something early on. :scratch2:

I've encountered problems with switches before. After many years of sitting around the contacts can oxidize. Sometimes working the switch a bunch of times can clean them up.

Check the resistance between the blades of the plug. It should be less than 200 ohms. If it ain't the switch start ohming the line wiring out.

There's a lid switch on these too if I recall correctly, make sure it's connected.

Eric,

There's a lid switch? I didn't know that, I will look up under that cabinet and see if I can find it.

Eric was right on with the lid switch! I didn't even see it and from the inside of the cabinet it looked like another control switch. Mine was stuck and after freeing, it powered up. Every tube but the CRT filaments lit up. Now to figure that out. At least I'm moving forward!!

Ok, after playing with the CRT socket, I've got the filament to light. The screen has not lit up yet. Now onto this problem...

Are you powering it up with the projection CRT? Be sure to keep it pointed away from you because of the X-Ray potential.
if it's in the barrel it should be pretty safe.

Yes, I'm testing it in the barrel, in the cabinet. Trying to figure out why my screen is dark. Undoubtedly a loss in high voltage, but what's causing it?

More often than not it's a lack of horizontal oscillator, I always start there.

Check for HV at the cap of the first HV rectifier (the one connected to the flyback) and see if you can draw an arc to an ungrounded screwdriver (a well insulated screwdriver).
Just hold it near it and you should be able to draw a blue arc about a quarter inch long.

I havea s small blue arc off the 1b3 connected to the flyback. Fm audio comes in loud and clear, but no raster.

Here is the section of the schematic either horizontal osc, output and afc....

If you have an arc at the cap of the 1B3 then you should have some HV, have you tested the 1B3's?

I can measure about 1000v off that particular grid cap. All three 1B3s test good.

Its probably not enough voltage to light the heaters in the HV rectifiers. You. Might still have a problem with the oscillator.

It could just be way off frequency. Or the B+ could be low.

Here's an updated picture of the set back together and on. Fm radio comes in great, but still no picture. Still trying to trace down why...?