Recently Acquired 1969 Motorola Color Tube Tv

[Lain94]

Last winter I acquired a 1969 Motorola Color Vacuum tube tv. HT-617CW is the service model number. D20TS-921-D02 is the chassis model number. It appears to be a VERY high hour set from what I know about it. The color driver pots are turned ALL the way up. The tv has changed hands many times in its life. Was once used in a barber shop for awhile until 1990 when it needed repair work done on it. The person I got it from fixed it back in 1990 and ended up keeping it after customer would not pay up for repairs. It was in use throughout the 90s through the early 2000s then sat in a basement in humid Massachusetts until Late 2021 when I was given the tv by the now very busy and retired repairman.

The tv did work when I tried powering it up with a variac. No issues at first but when I turned the tv off I heard a loud "pop" sound and upon examining the inside of the tv their were two burnt carbon comp resistors with char rings around them, along with a ceramic cap that was burnt up (locating right at where the mains voltage comes into the tv) It looks like a filter cap may have bit the dust and open shorted. The #2 wire fuse on the top of the chassis is also burnt out and gone, no trace of it left. The circuit breaker fuse also tripped. I already replaced the two burnt resistors but obviously that is not all that will be needed to repair this thing. It looks like it was NEVER recapped at all in its life as far as I can tell.

I have been on a waitlist since January 2022 to get this thing fixed at a repair shop an hour away in Mass. I have virtually zero experience working on vacuum tube electronics of any kind. I am more used to working on vintage computers which is my main specialty. I am really eager to get this thing fixed but am puzzled as to why it worked fine when it was turned on with the variac gradually but it shorted somehow when it was turned off after a few seconds.

Any information at all about this tv or what may have happened is appreciated.