Vintage RCA Projector Big Screen

[stushug]

I have an old RCA projection tv that I've owned since new. It's from 1981, Model PFR-100RW. One of the main reasons it got relegated to non-use was that it was becoming more and more out of focus. There is a built in grid you can use to do a basic alignment, but the focus problem is way beyond what can be corrected that way. What would be the first thing to try bring this set back to life somewhat? I've enclosed some pictures for reference. The mark on the screen has been there for years, caused by the mistaken use of some type of cleaning fluid many years ago.

[JohnCT]

Do all three tubes show the same exact focus problem?

Let it warm up about 15 minutes and look directly down the throat of each tube while you rotate the corresponding focus control for each tube. If the best focus is achieved somewhere within the control's rotation, you probably have weak CRTs or an optical lens issue.

If the focus improves at the end of the control's rotation but you run out of range, you have an electrical focus issue in the chassis.

IIRC, this TV was made by Hitachi and the focus for these was divided down from the second anode voltage using precision HV resistors in the focus/G2 block. Any change in value would raise or lower the focus voltage and push it out of range. These resistors are internal to the block and cannot be serviced. Finding a working block may be a problem.

If you can achieve pretty good focus within the control's range, try an optical adjustment. Block two of the three tubes with a towel (or book etc.) and loosen the wingnut on the barrel lens. Adjust for best focus on the screen, then repeat for other two tubes.

John

[stushug]

I'm not sure if the focus is the same for all three tubes. I will try what you suggested, and go from there. Thanks!

[stushug]

Originally Posted by JohnCT

Do all three tubes show the same exact focus problem?

Let it warm up about 15 minutes and look directly down the throat of each tube while you rotate the corresponding focus control for each tube. If the best focus is achieved somewhere within the control's rotation, you probably have weak CRTs or an optical lens issue.

If the focus improves at the end of the control's rotation but you run out of range, you have an electrical focus issue in the chassis.

IIRC, this TV was made by Hitachi and the focus for these was divided down from the second anode voltage using precision HV resistors in the focus/G2 block. Any change in value would raise or lower the focus voltage and push it out of range. These resistors are internal to the block and cannot be serviced. Finding a working block may be a problem.

If you can achieve pretty good focus within the control's range, try an optical adjustment. Block two of the three tubes with a towel (or book etc.) and loosen the wingnut on the barrel lens. Adjust for best focus on the screen, then repeat for other two tubes.

John

I found my service manual, and followed the adjustments they lay out. First I did the electrical focus, it was pretty good so there was not a lot of improvement. Then I adjusted the lenses and there was a HUGE improvement. The green tube was really close, but the blue and red were way off. We had pulled the set out to do some retro gaming with my granddaughter, and before the adjustment, on the NES you could barely read most of the text on any screen and the games were really out of focus. Now she can see everything and is having a blast. She's only 8 and before this she'd only seen PS4 type games but she's really enjoying the NES.
Thanks for the help John!

[stushug]

I tried today to get the picture centered, it was way off to the right. I could not get it right, now none of the guns are aligned, Every time I tried to redo it, I just made it worse. Does anyone know of a good repair guy in the Pittsburgh area?

[JohnCT]

Originally Posted by stushug

I tried today to get the picture centered, it was way off to the right. I could not get it right, now none of the guns are aligned, Every time I tried to redo it, I just made it worse. Does anyone know of a good repair guy in the Pittsburgh area?

There's a bit of an art to aligning a PTV. Not as bad as a piano tuning, but you get the point. Hopefully, you marked anything you adjusted so you can put them back.

First, treat this TV like a B&W TV. Cover the red and blue tubes and just work on the green.

There are centering ring magnets around the neck of the tubes, but they shouldn't be disturbed unless the CRT is replaced. If you moved them, see if you can put them back on the mark. Sometimes, the white snot they use to keep the rings from walking will be brittle and putting the rings back in position will be like putting a puzzle piece together.

If the green tube isn't centered, there are several possibilities. I recall problems with the hinges on some of those that would put the mirror in the wrong position. This will generally affect the vertical centering, not the horizontal.

There might also be adjustments on the convergence board for basic centering of the individual tubes, but again, these really don't need to be disturbed except for tweaking.

If the green still is off, it might be an electrical issue. Most of the problems we had with those were two thick film hybrid modules, but they either caused no vertical deflection (the vert hybrid) or shutdown (the power supply hybrid), so I don't think there's an issue there.

I think I tossed all those manuals but I'll take a look at my shop tomorrow to see if I still have any.

John

[stushug]

You're right about the white paint on the centering rings, I think I can get them back to where I started. I think you may be correct about the mirror being off and pushing the picture off to one side. I never considered that possibility. I guess I made it more complicated than it needed to be! I'll try your suggestions tomorrow. Thanks John!

[stushug]

I was able to get the centering magnets back in place using the white paint marks. Then came the nightmare of re-aligning using the convergence board. Luckily, the service manual gives the exact sequence for doing it. The problem was that I had everything so screwed up, that I had to go through each step many times, making small incremental steps. It seemed to take forever, but I got the set back to watchable. I still need to fine tune it, but at least I'm a lot closer than I was yesterday. I can't believe that I moved some many of those adjustments without making marks so I would know where I started. I know better. I doubt I'll ever make that mistake again!

[JohnCT]

The old analogue convergence systems were terrible to deal with. Most adjustments deal with geometry: trapezoids, parabolas, etc. Any adjustment on one area tends to affect the opposite side (if you're lucky) or the opposite corner (just as likely). Just follow the steps one by one several times and it will improve, and of course, do one color at a time. When adjusting the red, cover the blue lens.

But the more you play with the adjustments, the better the feel you'll get for the action and counter action.

The later point-to-point digital convergence systems were a dream. RCA probably had the very best digital convergence system with their last analogue PTV: the PTK 195 chassis. The 195 would put up it's own crosshatch, and when adjusting the red for instance, would extinguish the blue drive. Simply move the cursor from one point to another and move the adjustment with the quadrant buttons on the remote. Almost zero interaction with the point next to it.. A complete dynamic convergence took 10 minutes and was almost as perfect as a flat display.

John

[stushug]

i"m having a problem with the centering setup. The service manual says to use an Indian head or other image to center the image, but I have no way to generate one. This is supposed to be done before I finalize alignment with the convergence board. If I set the centering magnets back to where they were based on the white paint from the factory, the picture ends up off to the right. What can I try?

[old_tv_nut]

If you can tell it's off center without a test pattern, then you don't need a test pattern.

If you turn down contrast and turn up brightness (black level), can you see all four edges of the raster? I would want to make a quick check that it's a raster centering problem and not horizontal phasing.

I would say, if the raster is off center, then redo the centering adjustments without attention to the white paint. If, looking at the tube, the raster is centered and the picture content is centered, then you have neither a centering nor a horizontal phase problem at the tube; then if the picture on the screen still is not centered, it must be a mirror problem.

summary:
1) center raster
2) check for horizontal phasing problem
3) check mirror alignment

[JohnCT]

OTVN makes an excellent point that I'd like to expand on to make sure you understand what he's saying. If this is something you already know, then forgive me..

Sometimes, the actual video may be shifted even though the raster is centered - this is the horiz phase error OTVN mentions.

By lowering the contrast and raising the brightness, you can actually see the scan of the deflection circuits on the fact of the CRT. Alternatively, you can raise the G2 of the green tube a bit (not too far, and mark where it was) to see the raster. Look down the throat of the green lens. You will see if the raster sits right in the burn pattern the tube developed from years of running. With the TV on a snow pattern, you might see a slight overscan, which is normal, or slightly underscanned on a video input with no signal, which is normal.

If the raster is sitting more or less in the middle of the burn pattern on the face of the green tube, the deflection circuits and physical centering adjustments (ring magnets) are fine. At this point, you have a horiz phase problem. I don't recall if these models had a horiz hold, but it it does, you can see if that helps.

If the raster is off center, but otherwise full, you have a DC offset on the horiz winding.

Some TVs (Sony projectors) used a slightly different DC offset on each yoke, so mixing up the yoke plugs would cause a badly misconverged picture as the three yokes were nowhere close. I don't know if the Hitachi had this or not, but if it did, make sure the yokes are connected to the right colors on the board.

I tossed all my RCA manuals a couple of years ago so I no longer have that one. Is it on-line somewhere?

John

[stushug]

I started on it again this morning. I couldn't get the grid to align at all, so I put the magnets back to where they were by matching the paint markings. Last time I put the magnets back to factory marks I was able to align the grid. Now the grid is still way off and nothing I do seems to help. I attatched a picture for reference.

[JohnCT]

Originally Posted by stushug

I started on it again this morning. I couldn't get the grid to align at all, so I put the magnets back to where they were by matching the paint markings. Last time I put the magnets back to factory marks I was able to align the grid. Now the grid is still way off and nothing I do seems to help. I attatched a picture for reference.

Do the four controls have any effect? Remember, the green is stationary and only the red and blue move.

I know it looks like crap, but that isn't actually all that far off.

John

[stushug]

I had a service guy come over this morning, charged me $50 to tell me it's not worth fixing. That was all I needed to hear. I re-started from scratch and re-did the whole process until I got the grid almost perfect. Now I have the picture centered horizontally and vertically. The problem now is that the left side of the screen is perfect but on the right side I can see red and blue bleeding off to the right. It gets worse as you look from the middle to the right side. From the middle to the left side I can't see any of the red and blue bleeding. The bleeding doesn't seem to show on the grid, though.