#121
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I would like to point out that the Sams Photofact doesn't even show a 3.4 meg resistor in the regulator circuit. I'll pull my factory service literature tomorrow to look for running changes, but I'm not anticipating anything like that. Your set needs to be looked at by a competent tech, period.
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#122
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Evolution... |
#123
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Personal website dedicated to Vintage Television https://visions4netjournal.com |
#124
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Personal website dedicated to Vintage Television https://visions4netjournal.com |
#125
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I mentioned your recent comments to my friend Mike who has done 99% of the work on both the 21CT55 and the CTC-7. I myself can only do the basics. Mikes comments:
“The absolute high voltage rating for the 21AXP22 is 27,500 Volts and the design values are between 20,000 and 25,000 volts. I set yours for 21KV which produced good focus. And the Grid 3 volts (focus) volts will rise linearly with the high voltage since that voltage is derived from the tripler set of 3A2 tubes. And THAT grid has a maximum rating of 6600 volts which you do not want to exceed. And YES, the set will produce 30KV with the regulator pulled. I tested it that way when I was verifying the regulator functions. It does NOT mean that you run the CRT at that voltage!!! The regulator tube is, by definition, a SHUNT REGULATOR circuit. What that means is that it is designed to SHUNT the UNUSED high voltage to GROUND as a function of its design. There are no issues with capacitors as far as I could tell here. Are you having problems with the picture? You can look up the PDF file for the 21AXP22 if you want to learn more about its design values. There is a FUSE in the circuit to protect the flyback from overload in the event that it occurs.” I will ask Mike to join in on the conversation as he is a VK member. He just had long needed surgery, so it might not be to soon. Edit: I checked both the RCA and Sylvania data sheets and confirm the voltage figures cited by Mike. However, RCA states “25KV Max.”
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Personal website dedicated to Vintage Television https://visions4netjournal.com Last edited by etype2; 11-10-2017 at 01:35 AM. |
Audiokarma |
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This discussion is going to devolve even further if left open. I'm preemptively shutting this down for the time being. If another moderator sees reason to open back up have at it.
At this point, I think everybody has said their piece about the risks, real or "perceived", to Mr. Wozniak's flyback. There is little, if anything, to add to the discussion. Last edited by benman94; 11-13-2017 at 10:31 AM. |
#127
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I have deleted everything from this last day in an attempt to get this thread back on track.
If it can go forward in a more civil manner it will stay open. |
#128
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Recap of the restoration of a RCA 21CT55 without having to read the entire 10 pages of this thread. The set was fully restored last January, 2017. It took two years and we thank all the VK members who helped and especially Mike Doyle, also a VK member. In July we were doing a video of the 21CT55 and it was running continuously for about 4 hours. We were done and ready to shut the set down. I left the set running alone for no longer then three minutes for a bathroom break and after returning, found the horizontal collapsed about one third of the screen, badly converged color, and out of focus. No unusual sounds or odors present. I know, first rule, never leave a vintage set unattended. WHAT THE HECK HAPPENED! WHAT LUCK! After much testing, we thought the flyback failed. The set was only producing 10KV. That was a good sign. More testing with the HV probe and we pulled the regulator tube and found the HV measured 20KV. I can’t remember what the previous voltage was. That led us to suspect a resistor in the HV regulator circuit. We tested it and found it “open”. The suspect resistor was “buried” under the damper tube. This was done at my home and with lack of proper equipment and expertise, off the chassis went once again to Mike’s test bench/shop. Mike found the open resistor “buried” under the damper tube. He then addressed the color problem I complained about, weak green output. I blamed it on the somewhat tired 21AXP22. It still test “good” but on the low side at cutoff. It tuned out that a simple 1/16 turn CCW of a slug in the L44 Quadrature Transformer made all the difference. The green returned strong and looked good on Mike’s jigged CRT. The resistor was an original (made by International Rectifier) special film type, 3.4 Megohm 3 watt. Mike replaced it 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. Mike let the chassis “cook” (exaggeration) several hours a day for a week. During this time, he monitors the chassis for any anomalies, checks voltages, etc. The HV is 30 KV with the regulator tube pulled. All looked good and the chassis was delivered back to me. We reset the gray scale and did a full setup. We could not get the convergence perfect. Settled for good convergence in the center, top, bottom and left side. The bottom convergence is just as important as the center. Broadcasts usually show text at the bottom. The 21AXP22 looks like a new CRT now. We are happy! Operational observations: The set comes up with good convergence and seems to reach full brightness in 30 seconds. The image enlarges to a point that after about 25 minutes the annoying Macrovision streaks on the “Gentlemen Prefer Blondes” DVD disappear at the top of the screen. The cabinet is in good shape but we will refinish the top which has blistering of the old varnish. We still have to polish the brass trim around the CRT safety screen. Here, a few more screenshots from the 1953 Technicolor movie, “Gentlemen Prefer Blondes”. I’m very pleased with the results. This link will open an image carousel and full resolution images of the thumbnails can be viewed. https://visions4netjournal.com/vinta...-carousel-3964 This link will show images from OZ and THE RED SHOES. https://visions4netjournal.com/vinta...-carousel-3856 If anyone has a copy of the “Service Clinic” booklet for the 21CT55, I’d appreciate it. I checked the ETF and internet. Nothing found. I would like to address the concerns expressed about the HV by several VK members. The resistor failure concerns me but then again, it’s a 62 year old set. Things fail. We can’t replace every single part. Thanks.
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Personal website dedicated to Vintage Television https://visions4netjournal.com Last edited by etype2; 11-12-2017 at 10:01 PM. Reason: Correction and addition. |
#129
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http://www.earlytelevision.org/Deksn..._6BD4-6BK4.htm In short, pin 8 on the 6BD4 socket in the CT-100 is used as a tie point. It is not used as a tie point in the 21-CT-55, so you can use any 6BD4A, 6BK4, or 6EL4A you choose. |
#130
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Regarding the correct 25 kV ultor voltage, see this quote from the RCA booklet entitled "Technical Features of the RCA Victor Model 21-CT-55 Color Television Receiver":
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I'm still failing to see what is ambiguous about the RCA specified ultor voltage, but to be honest I really don't care any more... I tried to help, I only hope you correct the issue before your flyback goes up in smoke. Anyway, here is the factory service data you asked for "1954 No. T13", published November of 1954: http://docdro.id/HBjbl9P You'll note that the only 3.3 MOhm resistor is in the grid circuit of the triode section of the 6AN8 that serves as the R-Y amp and phase splitter. I'm not sure what resistor Mike replaced in the 6BD4A circuit with two 2.2 MOhm resistors in series. Apparently he's smarter than RCA's own engineers. I guess we should all defer to some random guy with a soldering iron instead of the factory service literature... |
Audiokarma |
#131
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Thanks for posting the RCA info. It will be nice to be able to reference in addition to the sam's folder.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#132
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Thanks for posting the link and the “T13”. There was a reference earlier to the “service clinic” or “white book” booklet. Do you have that as well?
I’ve have the service clinic for the CTC-7. I have the Sams for both sets and the “Field service guide” manuel.
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Personal website dedicated to Vintage Television https://visions4netjournal.com Last edited by etype2; 11-13-2017 at 06:58 PM. |
#133
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To my knowledge, these are the only two official service documents regarding the CTC-2B. There may be others that I'm unaware of, but I doubt it. I believe Nick has a copy of the Service Clinic, but given how dismissive you were of his attempt to help, he probably won't bother to post it. I wouldn't blame him either... Last edited by benman94; 11-14-2017 at 04:28 PM. |
#134
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Uh huh, and what does Sams say to set the anode voltage to on page 14???
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Evolution... |
#135
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I'm going to hazard a wild ass guess... is it the same value found on page 17 of the factory service manual I uploaded?
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