RCA 21CT55 B8802897 is Alive!

[Tomcomm]

Bob G........Somehow I didn't realize you were the "Bob" of the recent, most impressive full restoration of all 21CT55s. Since you did a complete recap I would expect yours to have the least problem with warm-up drift. I assume you Quick Freeze'd all resistors in both deflection systems and the complete convergence chassis? I can imagine your frustration when you fire-up your beautiful 55 for some TV-wise visitor and it comes up greatly miss-converged. I have the same problem but I never have demonstrated my 55 to any knowledgeable visitor, so waiting 30 to 60 minutes warm-up before taking critical screen shots is no big deal. I've asked this forum's members that have early RCA tube CTVs if they had similar problems and received zero replies. Must be you and I have a unique problem or others are unaware they have a problem or have little interest in the subject?

I checked my power transformer and horizontal output transformer tempts after over 3 hours operation on 113vac mains input on a hot day. The B++ was 410v, Boost was 900v and ultor was 30kv. The horz output tube input control was set for minimum drive and the horz B++ current was 320ma, horz output transformer was 113deg and the power transformer was 140deg.

I will continue freezing all critical resistors and caps looking for sensitivities as soon as my five cans of quick freeze arrives next week. Of course I will report any interesting results.....Tom

[Pete Deksnis]

Originally Posted by Tomcomm

I've asked this forum's members that have early RCA tube CTVs if they had similar problems...

As I am sure everyone is aware, the CTC2B chassis is an outgrowth of the CTC2; the two chassis have far more similarities than differences.

When I need to view my CT-100 (CTC2 chassis) critically, I never do so without a bare minimum of 30 minutes warm-up, with one hour typical. In particular, fine color balance is not achieved without the warm-up time. I often wonder if a 'time-warp-acquired' set of just-manufactured tubes from RCA Harrison would shorten the warm-up requirement. My sense is that the 55-year-old 6AN8's and 12BH7's require more time to stabilize than when they were new, even though the time on them is not great.

Pete

[ohohyodafarted]

Hi Tom,

Thanks for the info on the HO trans temp and B+ current. Yours seems to be running nice and cool. That gives me a good benchmark to shoot for. I just got back from a vacation and my freez spray has arrived, so I will try and find some time to look for temp drifting resistors this week to see if I can nail down the large shift in convergence at startup. The funny thing is that after half an hour of running, when the convergence has stabilized, I can turn the set off for 15 seconds or so and the convergence drift will re-occur. But it will re-stabilize in about 2 minutes.

John Folsom has told me that I should replace the flat green power resistors. John says that these type power resistors are known for being a problem. That is the next thing I will try.

Thanks again for the data on temp and voltage/current readings. I will post again as progress is being made.

Bob G.