RCA 21CT55 #8802897 is Dead

[Tomcomm]

I originally posted the following message on May 30, 08 when my 21CT55 seemed to be performing at its best. It gave me the opportunity to rationalize why I did not restore it to original, since I destroyed the cabinet in making it into a table model to save space in my garage workshop in 1964........................


.................I decided in October 2007 to reactivate the beast after 40 years in attic storage and use it as a test bed to determine and demonstrate in photos, the picture quality this 55 year old RCA CTC2B chassis was capable of producing. As such, it was not constrained to replicate the original circuitry in every detail or even operate to the '55 RCA spec. I jacked up the +400v B++ supply to above +420v with silicon diodes and got a horz boost of almost 1KV. I intend to start reducing the CRT Ultor HV from its present 34KV to the 28KV range while doing a full convergence at each reduction level to determine if I loose ANY picture quality.

Since I'm running the 21CT55 as a composite monitor, I disabled all the tuner, RK/IF and audio portions and opened all unnecessary tube 6.3v heater strings to allow the power transformer to run much cooler. I left all inactive tubes in their sockets and documented all changes for immediate reactivation. Yes, I brutalized this valuable historical item but there are at least five other 21CT55 restorations on this forum alone. I believe I've succeeded in my goal of demonstrating the 21CT55's ability of displaying exceptional picture quality.

http://s677.photobucket.com/albums/v...2021CT55%20TV/

I do intend to refinish the surviving front panel of the original cabinet using the approach described by Bob G in his impressive restoration. I might even attempt to construct a pseudo pencil-box control panel,

On March 21, 2010 at 3:30pm my 21CT55 ate its flyback transformer in a cloud of acrid smelling white smoke coming out of the HV cage! I was out of the room for about 10 minutes so I didn't see it loose its picture and couldn't shut it down, so it just cooked. I was so shocked, I just killed the power without looking at the HOT and damper to see if their plates were red hot. I opened the cage and the FBX was still smoking. The HV doughnut was dropped down and dripping hot insulation stuff, a truly sickening sight. The B++ fuse had not blown because it was 1 amp! It should have been .5 amp since the running current was only 265ma. I checked my fuse box marked .5 A and the 4 remaining fuses were all 1 amp, bummer!

I lifted the doughnut back to where it should be, supported it with pieces of foam plastic and let it cool off for about 30 minutes. I put a current meter in series with a .5amp fuse and applied power. Remarkably, the boost voltage and B++ started to slowly climb and the picture came on as the current settled at 265ma, boost reached 780v, ultor was 27kv, all normal! Naturally, I was delighted. After about 5min,the screen went black, the current climbed to 480ma and the boost dropped to the B++ of 420v. The HOT plate started to glow so I shut it down. The FBX was warm. I pulled the damper, the yoke and all the HOT and rectifier plate caps and power up'd. The HOT grid had a normal 150vpp drive input, that was not the problem. All FBX windings measured nominal resistances, maybe they developed shorts? Anyway, I needed a CTC2B FBX, apparently a non obtainable item. So was this the end of my 21CT55?

Do any members have an operational CTC2B flyback transformer or know where I can acquire one? If so please send me a PM with details ......soon. Thanks, Tom