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21CT55 Stability Time
My reactivated 21CT55 has been operational for over 18 months with no problems except.......it takes about 30 minutes for the screen to reach acceptable size and convergence after cold morning power start up. It takes an additional 60 minutes to reach near perfect vertical linearity and final convergence suitable for critical picture capture.
I use the Digital Video Essentials' crosshatch with circles pattern to evaluate this problem with black felt pen dots on the CRT screen after the sets been running about three hours. The dots give a very good indication of circle size and linearity. A few pen lines indicate where convergence is less then perfect. Results have been consistent the last three mornings so what components has a 90 minute thermal time constant? I've already replaced the tubes and at least five capacitors in the vertical osc/amp circuitry and always keep the B++ buss set for 410v with my AC input Powerstat. Boost stays at +880v and the ultor runs about 30KV.
Hey, I'm not overly concerned and can live with the long warm up. It's not a
restored show item, just a hobby toy. Any comment or suggested fix is welcomed......Tom
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