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The Set: Pete Deksnis's Site about the CT-100

Restoring a Vintage Color Television Set

THE SET

info exchange

8-99 My set has a 270K resistor too on the 12AU7.

9-7-99 After changing all the paper caps, I slowly brought up the power supply on my set with no load. So far, all the elecrolytics except one seem ok. I have the proper voltages, too. The wirewound pot for the field neutralizing coil was open, so I repaired it.

10-18-99 I don't know if you noticed the CT-100 on Ebay last week. It was hidden because it was listed as a CTC-2 "colour TV". It has been in storage since 1972, when it worked. The cabinet is supposedly mint, and it comes with a spare, NIB 15GP22. I couldn't resist when, with one hour left, there were no bidders. So, I bid the minimum and got it.

10-23-99 Well, today was the day. I put my new tube in the cabinet and installed the chassis. I immediately got a raster (after fiddling with the screen controls). I then did a quick purity adjustment and got a more or less red screen. Then, I did a static convergence.

And, IT WORKS ! I have a decent color picture. Obviously, I need to go back and do the purity again, and do the dynamic convergence.

I am going to experiment with disabling the waveform to the convergence grid to
see how the convergence is. If it is tolerable, I may have my 15GP22 rebuilt with one of the newer guns.

10-31-99 I installed some fuses to protect the set as was recommended by Tom. I did it a slightly different way, though. I bought a 4-fuse strip from Radio Shack and mounted it directly to the right of the ballast tube. I then moved the two fuses that are soldered in behind the ballast to the fuse clip, and added a fuse for the 285- and 275-volt lines. I left the fuse wire in place for the filaments, but I did install a fuse in the cathode of the horizontal output tube.

I came up with about 180 mA for the horizontal output fuse, 260 mA for the 285-volt line and 120 mA for the 275-volt line. So, I am using a 1/4-watt fuse for the horizontal output and the 275-volt line, and a 1/2 watt for the 285-volt line. So far, they haven't blown.

I did a more complete convergence and screen balance, and came up with a pretty nice picture. Also, I unplugged the 12AU7 vertical convergence tube and turned the horizontal convergence amplitude to minimum. The convergence looked pretty decent. It may be that the 15GP22 could be rebuilt with the 21 inch gun and work pretty well.

11-3-99 I got email from someone who has restored about a dozen CT-100s over the years. He suggested a product called High Vacuum Leak Sealant from Space Environment Laboratories in Boulder, Colorado.You spray it on at the metal/glass junction.

He also suggested that a center-tapped filament transformer be installed with a relay, so that 3.6 volts is applied to the filament of the picture tube when the set is off and the full 6.3 volts is applied when the set is on. He says that the tube is full of iron hardware that will emit gas; heat from the filament will keep the gas at bay and also prevent the sudden surge of current to cold filaments. This will greatly extend the life of the tube.

I bought a complete CT-100 chassis, plus some other spare parts from him, so I now have some spares. If you come across something you need, let me know.

3-21-00 I was checking out your website tonight and noticed the speculation about the CT-100 in the RCA ad.

I know where that set came from.

When I was visiting the Thompson headquarters in Indianapolis last fall, they were in the process of taking the 15GP22 out of the CT-100 they have in their "Museum" (actually a lobby) so that the set could be shipped to Hollywood for a commercial. The tube remained in Indianapolis.

On another topic, I am now restoring a Philco TV-123, a 1955 21 inch set with a 21AXP22. About 500 of these sets were made. The picture tube is good, and the cabinet is in great shape. Right now I am waiting for some tubes I need to complete it.

4-22-00 Thanks for the info. I have made a deal with someone who has 2 Westinghouse sets - I will restore them both in exchange for one of them.

On the CT-100 low HV problem, has he checked the B+ voltages? The selenium rectifiers in those sets are almost always bad. Also, where 50-Hz power us used, if the B+ is low, I wonder how well the power transformer will work on 50 Hz. It wasn't designed for that, and may be inefficient. One could boost the input voltage to compensate for it, but would have to watch out for overheating. Beyond that, about anything in the horizontal section could cause that. Check for the proper drive waveform and amplitude on the grid of the horizontal output tube; replace all the capacitors, and try the HV rectifier tube. Finally, HV probes are often not too accurate. Is there something to check it against?

My Philco TV-123 works now. The picture on the 21AXP22 is very inferior to the 15GP22.

6-11-00 On the problem with HV on the CT-100, my Philco TV-123 had a bad HV "button" capactor, which lowered the HV substantially.

I am now restoring two Westinghouse H840CK15's. I made a deal with someone who's dad was a TV serviceman in the 50s and bought the two sets. I am restoring one for him in return for the other one. One has a good CRT, the other is full of air. I get the bad CRT, but hopefully Bruce will be successful.

I have recapped one of the sets, and am slowly getting it working. I am down to one problem -- the color is inconsistent across the screen. For instance, a person's face appears blue on the left side, green in the middle, and just right at the right side of the screen. It is not a purity problem, it has to do with the color sync. I have asked Rob for a copy of his factory manual, since I have checked everything using the Sams, and have done the alignment on the 3.58 oscillator using the instructions in Sams.

6-13-00 The first chassis is working, but there is still a problem with the color. The second chassis
works great , so I can compare waveforms, etc. to get the first one working. Here is what I had to do to get them going.

EACH CHASSIS
-Replace all paper caps
-Replace 6000-volt caps in focus and convergence circuits
-Check all tubes
-Spray all tube sockets and controls with contact cleaner
-Check all electrolytics using an in-circuit tester

CHASSIS 1
-5 bad electrolytics (one leaky and the others low capacity)
-1 bad power resistor
-Bad height control
-Bad mica capacitor in color burst circuit

CHASSIS 2
-3 bad electrolytics (low capacity)


6-25-00 I have been out of town for the last two weeks, but will return to my other Westinghouse this week. I found a neat tool for anyone doing color alignment, etc. It is called the Calibar, and is a professional quality digital pattern generator about the size of a pen. It produces 24 different patterns, including color bars, grey scale, crosshatch, red, blue, and green screens for purity, etc. It costs $275, but that is less than a professional quality rack mounted unit. Here is their website:

http://www.newtek.com/products/calibar/description.html

6-27-00 I found the problem with my second Westinghouse chassis. The Sams alignment instructions were not very clear, and I finally found the proper way to align the color demodulators. The colors are now really good -- better than the CT-100, I think.

The Westinghouse uses R-Y and B-Y synchronous detectors. [
Here's a LARGE but simple block diagram (70 KB) from Steve of the Westinghouse H-840CK15 ]. It also doesn't have a 3.58 crystal -- it uses a tank circuit. I wonder why everyone went to a crystal -- the tank circuit seems to work fine, and it had to be cheaper than a crystal.

I am attaching a photo of the color bar pattern from the gadget I mentioned earlier.

While I was messing with my first chassis, the focus went bad, and I found that the vertical convergence transformer had broken down. I was horrified until I looked in Sams and found that the CT-100 uses the same part number, and I have a spare CT-100 chassis with a transformer (good, I hope).

7-22-00 I have had two bad .005 mfd 30 kv capacitors, one in my Philco TV-123 and one in my Westinghouse. I have found a source for almost original (slightly smaller, but the same style and with screw terminals). They are not cheap -- around $50 each. If anyone needs to know where to find them, they can contact me. [Steve's email: stevemcvoy@gmail.com]

2-7-01 I finally got a chance to study the two 15GP22-based Dage model 650A color studio monitors. I plan restore one, using parts from both.

First, I removed all the brackets and faceplate stuff from both chassis. Then I inventoried the critical parts: Both yokes are OK, both power transformers are OK, one flyback appears to be OK (resistance checks OK), and I have one good focus pot and one good convergence pot. I don't know yet about the convergence transformers or the vertical output transformers. A dud picture tube from one had been sold recently on ebay before I acquired these units. The other tube has a
broken neck.

I have one field neutralization coil and one convergence assembly.

Both chassis have rust, one worse than the other. I'll use the best one and maybe have a plate welded on the side with the bad rust. The front panels of both are rusted. I'll probably have a new one made. The front cover is aluminum, and I'll have it repainted.

They have this tube lineup:
2 - 5V4 rectifier
3 - 6CB6 video amplifier
3 - 12BH7 video ouput
1 - 6BJ7 DC restorer
1 - 6SN7 horizontal oscillator
1 - 6CD6 horizontal output
1 - 6AU4 damper
1 - 1X2 focus rectifier
1 - 3A3 HV rectifier (notice that the set doesn't use a voltage doubler like the Westinghouse.)
1 - 6BD4 HV regulator
1 - 12AU7 vertical oscillator
1 - 6BL7 vertical output

The inputs are sync, R, G, and B (no composite input). Next, I'll replace the capacitors and fire it up. I'll keep you informed.

See more of Steve's early television equipment at his site


2-14-01 Here is a progress report on the Dage. I plan to restore it one section at a time, to minimize the boredom of recapping the whole set at once.

I started with the horizontal section. First, I put the HV section together, using parts from both sets. Then I recapped the horizontal section. I then fired it up on the variac, with only the rectifiers and horizontal oscillator tubes in. After about a half hour, two electrolytics started smoking, as did a couple of paper caps in the other sections. After replacing these, I slowly debugged the horizontal oscillator. I was surprised to find that almost all of the mica capactors were leaky. I've never seen this before. So, I ended up replacing every cap in the horizontal oscillator section. After that, it worked.

I then installed the horizontal output and damper tubes. I had about the right voltages on the cathode and grids of the horizontal output tube, but no high voltage arc at the cap of the HV rectifier. Then the width coil started smoking. I replaced it with the one from the other chassis, and I had a nice arc. I put in the HV rectifier, and I now have 20 kV dc.

Next, I'll get the HV regulator and focus rectifier working.

After that, I'll recap the vertical section and get that working.

Then, I'll recap and debug the video amplifiers.

Finally, I'll work on the convergence stuff.

2-16-01 Well, the Dage is almost done. First, a couple of changes in the tube lineup:

1/2 of the 12AU7 is a sync amplifer, the other half is the vertical oscillator. 1/2 of the 6BL7 is the vertical output, the other is the convergence amplifier.

The vertical, horizontal, and HV schematics are almost identical to the CT-100. In fact, it looks like a CT-100 flyback, yoke, and vertical output transformer. The only difference is that there are 6 adjustable inductors in the width/horizontal linearity circuits to allow for more accurate linearity adjustment.

The video section consists of a 6CB6 preamp, 1/2 of a 12BH7 as a cathode follower, and the other half as the video output. 1/3 of the 6BJ7 is the DC restorer (one set for each color).

Debugging the vertical section was easy. After changing the caps, the frequency was about 600 Hz. The problem was a bad vertical blocking oscillator transformer, which I robbed from the other chassis.

Debugging the video sections was also easy. After changing the caps, the only problem was a couple of open peaking coils. I have one bad tube socket to replace, but otherwise I have good video at the CRT socket.

The only other thing to do is trace the convergence circuits and understand how they work, then check them. They are fairly simple, so this should be easy.

My
Zenith 15GP22 should arrive in the next couple of days, and I plan to have the Dage ready to install it in and test it. The only thing I need to do is get some sort of video source that has RGB and sync outputs.

Some more on the Dage. I replaced a pin in the bad tube socket, so now the video is done. I traced the schematic of the convergence amp, and it is now working.

Until I get a new metal front made, I have reassembled the monitor with the old one. Actually, the aluminum face hides the rust. I put back all the control extensions, and the mu-metal shield for the CRT.

The glass faceplate is broken, so I'll get a new one made by a local glass shop. The aluminum face is not too bad, so I may just clean it and try some metal polish. It won't look like new, but not bad. When I get the 15GP22 in it, I'll take some pictures.


3-3-02 I was working on a CT-100 chassis recently, debugging the video amplifier section. After a couple of hours of messing around I discovered that there is an error in the waveforms shown in the Sams folder 252-11. Waveforms W1 and W2 on page 3 are inverted. W1 should have the sync pulses up, and W2 down.

4-14-02 I recently did an alignment of the color AFC and reference oscillator sections of two CT-100s. In the process, I learned some things that will be helpful to other collectors.

I have found that after following the alignment instructions in both Sams and the RCA service manual that the color rendition is wrong. I discovered by trial and error that adjusting L41 (A39), the burst amp output transformer, will bring the colors in correctly. Set the hue control to midrange and adjust L41 until the colors are right. I use a color bar generator and look at the I and Q phase inverter outputs for the proper waveforms. Do this after you have completed the standard alignment.

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