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  #16  
Old 01-18-2018, 12:37 AM
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ohohyodafarted ohohyodafarted is offline
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Tom,
Looks like you are comitted to putting in a huge effort on this set as you are intending to re-stuff the paper caps etc. It would be a shame after all the work you are going to put into this set if your flyback took a dump.

With that in mind you can take this advice and do what you will with it. During the restoration of my CT55, my flyback took a crap. I was able to obtain a replacement due to the generosity of John Folsom who was probably the only person in the world with a NOS replacement flyback for this set. Later on after I got the new flyback up and the set was running, the HV went down again. This time it was the 30KV doorknob. I obtained a new 40KV 2000pf replacement and with some small hardware mods it replaced the original quite nicely.

Upon reflecting as to the cause of the failure of the original flyback, I came to the conclusion that the original doorknob was probably leaking and placing an extra load on the flyback. Combined with the poor ventilation of this HV cage desing, it was more than the flyback could endure. More recently, I was involved with the replacing of another one of these failure prone doorknobs in the 15" GE color set that came from Colin Wood.

I see from your photos on Flicker, that your flyback appears to have been overheated. I can see from the photos it has sagging wax and drippings.

If I were in your shoes, I would buy some insurance.

Get a new 40KV 2000PF doorknob and replace the OEM POS that is in your set presently, to insure that you have a doorknob that is not leaking.

IN addition, the HV cage on this set is very poorly ventilated. Get a small muffin fan, cut a hole in the side of the HV box and force cool that flyback.

Your flyback has already been punished enough from sitting inside what is basically an oven. Don't take a chance on killing your flyback. Almost anything else in this set can be replaced, if the flyback takes a dump you will kick yourself around the block if you did not take some prophylactic measures to safeguard it. And it could fail even if you do.

My flyback runs cool as a cucumber with the new doorknob and force cooling the HV cage with the muffin fan. Go for a fan that has a very quiet sound rating instead of a high CFM. With the volume set at a normal listening level you will not be able to hear the fan running.

Good Luck
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  #17  
Old 01-19-2018, 01:15 PM
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etype2 etype2 is offline
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Very good advise from Bob. It astounds me how any of the components can survive literally mm’s from heat producing tubes. A recipe for failure. We also added a fan in our 21CT55 by cutting off the “chimney”. The hole is already cut in that location. Added a switch to shut it off if needed. As an added precaution, the power is regulated with a Furman power conditioner.

We had a failure after several months of operation. Suddenly lost convergence, focus and the picture shrunk. “Oh no, the flyback!” We traced the problem to an open resistor buried under the damper tube.

The High Voltage was reduced to 10 KV with this failure. It now adjusts nicely from 18 KV to 21 KV as it should. (Edit: Mike saw 25 KV, set it to 21.5 KV) The resistor was an original (made by International Rectifier) special film type, 3.4 Megohm 3 watt. It was replaced with QTY 2 (in series) OHMITE 2.2 Megohm 2 Watt film type which now makes the new resistor a 4 watt unit which is a 25% upgrade for power dissipation.

Did you check the serial number stamped on the wood pull out under the pencil box? Wishing you continued success in the restoration.

A few photos of the bad boy resistor, replacement and fan:









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Last edited by etype2; 03-29-2018 at 01:34 PM. Reason: Typo discovered
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  #18  
Old 01-20-2018, 11:24 AM
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Electronic M Electronic M is offline
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Before the HV reg (more specifically that 4.5M resistor feeding its grid that Etype mistakenly refers to as a 3.4M above) was identified the large doorknob cap was briefly my prime suspect in the low HV issue. If that doorknob is a high failure part as you imply then I will look into replacing it. Since the first powerup, I have been running the set with all removable panels of the HV cage removed for maximum ventilation and ease of access...I suspect that may be contributing to the reception issues. I will be considering means of improving air circulation. If possible I'd like to refrain from putting holes in the original metal so I may make modified replica sides for the HV cage as mounting points for the fan(s).

Since I had some good free time until the end of this week the goal was to do as much as I can. I started a new job late this week...Between a swap meet this weekend and work it may be a while before I can sink more time into this, however, I'm pleased I was able to get this far in the time I've spent.
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  #19  
Old 01-20-2018, 05:33 PM
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Tomcomm Tomcomm is offline
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Deflection System Cutoff Switch

Off to a great start with your complete restore to original restoration. I'm impressed with your progress so far, even to re stuffing failed capacitors!
From my experience with this beast, I would advise mounting a single pole toggle switch in series with the +400v deflection system fuze.The rear chassis near the HV adjust pot is were mine is. This "kill switch" would enable instant HV system shutdown and restart without taking the entire 21CT55 down and have to wait for a complete TV start up. During work on the deflection system, I never leave the room without killing the + 400v power! I might be a slow learner, but not that slow.
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  #20  
Old 01-28-2018, 12:51 AM
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Soooo....Things have been happening.

So first the bad news: my Blu-ray player has the zoom settings in a retarded state that pillar-boxes 4:3 content to have bars on the sides, and I don't have a remote to fix that menu setting....

The good news in video form...Click to visit then click to watch:

Of all the Model5/CT-100/21CT55 screenshots and videos I've seen on the internet, I can't ever recall even one showing the RCA CED/Selectavision intro theme being fed to one of these sets....How this has not occurred to anyone before I can't fathom....But I can put two of RCA's coolest engineering achievements together, and let people nerd out to it.

And now some obligatory Wizard of OZ screenshots:


'How did it get to this point?' you ask....Well After rearranging some stuff I decided to move the cabinet to the workbench gather/make extenders for the yoke, CRT and speaker (but not the dynamic convergence...That reaches if the chassis is not mounted), and then go about dipping the H out cathode current with the osc in sync and it's waveform correct. I dipped the current using the linearity and drive controls. It is at a steady 217mA with the B+ at 390V....I've found the B+ affects it too. I decided to dip the B+ to 375V where the cathode current is around 205mA....Running it that way for an hour the fly is just slightly above my body temp which I think is quite a healthy temp for it.


I then adjusted the vert section and centering and fed it color bars....I was VERY disappointed and confused. The color bars made NO sense at all and adjusting the tint did not help. I also had to super glue the red static convergence knob back on to the magnet. It broke off with a gentle twist.... I went on to check the tuner on channel 7 and 13. Seven got nothing and 13 did not improve, but I discovered 12 will pass sound from 13 and the monochrome video....It will also pass the local NPR station(I can see the tower and tune it on otherwise dead FM tuners) on part of the fine tuning range on channel 12. What is up with that?
That all (except for the hour run) was Wednesday and I gave up for the night.

Earlier today I decided to get back on it. I decided to do the purity adjustment. I did try to prep for it Wednesday, but the screen controls did not kill any gun or work as expected in terms of color change. I found it easiest to short the B and G grids to ground to leave only Red...It did not look red at all, but what the hell. First try I got much more red on the screen, a few back and forths with static convergence, purity rings and eventually the face magnets, and I got it fairly good (worst primary pictured)....Best yet I turned up the color adjusted the tint and got good SANE color bars. It seems the purity was SO far off before that the guns were all completely scanning each others phosphor!


I then pulled the vert tube, shorted the CRT grids together and grounded them through a 100K resistor. I set R and G to produce a reddish yellow (ISTR hearing these sets were meant to have a slightly reddish grey scale) then blue for white. I then removed the jumpers. plugged the vert tube back in and adjusted the B and G drives for slightly reddish whites. I need to figure out the B and G balance controls (I adjusted the outer one by accident).

So far it is REALLY good. If the RF/IF system would only pass color I'd be about content with performance.

I need to order new resistors for the focus/HV reg system...I also need a need a new HV probe...My favorite/accurate one fell off this set 4' onto a concrete floor and shattered. That probe probably saw 8-10 years of service since I got it (plays taps softly).

BTW / PS I added pics of my video amp and the contrast control/it's kludge replacement to an earlier post on the first page of the thread.
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  #21  
Old 01-28-2018, 01:44 AM
EdKozk2 EdKozk2 is offline
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Tom, you've made great progress on your CTC2b set.
Ed
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  #22  
Old 01-29-2018, 10:20 PM
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Electronic M Electronic M is offline
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Thanks Ed.

I did some more fooling around and found the IF will pass color, but the fine tuning setting for that makes the luminance and sound noisy. For now, at the very least it is an awesome monitor...with a tuner that has issues.
DSCN2989 by Tom Carlson, on Flickr

I want to improve a few small things, then I'll have to decide whether to deal with the cabinet or alignment first.
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  #23  
Old 01-31-2018, 09:12 AM
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miniman82 miniman82 is offline
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Quote:
Originally Posted by etype2 View Post
The High Voltage was reduced to 10 KV with this failure. It now adjusts nicely from 18 KV to 21 KV as it should.
Once again, the HV specification for the 21-CT-55 is NOT 21kv. It is 25, please stop spreading misinformation. If you want to run your own set that way, that is your business. Don’t misquote service literature to others.
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  #24  
Old 03-29-2018, 12:08 PM
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benman94 benman94 is offline
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Quote:
Originally Posted by miniman82 View Post
Once again, the HV specification for the 21-CT-55 is NOT 21kv. It is 25, please stop spreading misinformation. If you want to run your own set that way, that is your business. Don’t misquote service literature to others.
Amen.
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  #25  
Old 03-29-2018, 06:13 PM
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Some reading the thread might buy that 21KV non-sense, but unlike them, I read my service lit and know it is 25KV.
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