Restoring a RCA 21CT55

[Findm-Keepm]

Originally Posted by benman94

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":



(Emphasis added by yours truly.)

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...

From 1954......hmm... do you have the 13 Goldenrods (service Bulletins) issued against the 21CT55? (I don't either...) The last one was issued in 1972....and probably a parts stoppage report. Many of these Goldenrods were safety issues - without them, the original service literature is a snapshot in time.

By 1978 (when we got our first RCA service library, from RCA, 28 binders, TV only...), some 600+ Goldenrods had been issued by RCA for televisions. Some were minor part number changes, but in the case of ALL early color (CTC17 and earlier), RCA issued Goldenrods to limit the 2nd anode voltage in all sets to a value that reflected the amount of shielding around the regulator tube.

I'm not Chicken Little, crying about the X-rays - I'm merely pointing out that the original service lit has been revised many, many times and some original statements and values rescinded.

RCAman, a frequent poster, may still have an RCA library with the Goldenrods. Ours went the way of another shop when we closed up in 2008. They tossed all the tube stuff - I rescued what they still had - CTC72 and up, unfortunately.

Nick/Miniman82 - same as any NAVAIR pub change - remove the old stuff and put in the new, up-to-date stuff. Old values/procedures and part numbers no longer apply...