So I've been busy on the combo...
IMG_20240725_235219342_HDR by
Tom Carlson, on Flickr
Getting close to finished now. However there are some yoke parts that it needs that I don't have.
http://videokarma.org/showthread.php?t=276746
The TV was a fairly straightforward resto. I shotgunned all the paper, film and lytic caps and all resistors that had drifted high and it begrudgingly came to life...The first variac session was stopped by arcing that I traced to a aired out HV reg tube arcing internally. Damn thing came apart in my hand when I unplugged it. After fixing that I was able to eventually get focus and H-hold good enough to get a synced picture from my B&K on IF injection mode then had to work on the tuner. It was so dirty In had to play with it to get any signal and signal would fade out after a few minutes on... cleaning the contacts got solid signal but the time fade persisted which experience accurately told me was a weak tube in the tuner....there were still mechanical issues in the tuner though. It had the typical remote control motor with a stuck shaft issue (unstick and lube and your golden), and several issues with the fine tuning. The belt was bad (hardware store O-ring fixed that) the shaft that goes into the tuner housing was stuck (had to hit it with penetrating oil and vice grips to work it free) and the fine tuning gear that meshes with the channel strip gears was starting to disintegrate.... Luckily I have some Zenith tuners of this era and basic design and was able to harvest a good gear from mine.
Then I had good color and video...however no sound. It seems like the output transformer primary was open (had no plate voltage and it checked open) however when I started poking around trying to see if the open was somewhere I could get to and fix continuity magically returned and it started working :shrug: All I can figure is a cold solder joint on the tube socket (I did retouch those joints to be safe)...I could not make it relapse so I'm going to hope it stays defiantly good.
Even if it does at some point relapse the speaker relay is wired to switch audio from the TV to the stereo when the stereo comes on so if the video source he has has line level audio he can plug it into the tape input if the stereo and have objectively better audio then the TV ever had. (I get the feeling Zenith anticipated stereo FM/TV concert simulcasts of the 70s and 80s with this design)
The remote receiver just worked on my 2 test remotes post recap...I did have to bend in the dormant return limit on the volume stepper to get it close enough for the field to pull it in. After that it didn't always ratchet/close fully, but then I remembered that on these roundy color remote chassis that if they're not oriented the way they're supposed to mount in the set (which uses gravity to aid stepper pull in) they normally act weak... changing from convenient bench mounting to inconvenient but correct set mounting orientation got it 100%.
I'm about to test all the tubes, try and replace the red screen pot (it's all or nothing like the carbon track is open), do the H linearity current dip (not sure In need to since current is a very safe mild 110mA), set HV regulation (it's a touch low), and go back to the radio chassis and replace a couple of damaged FM MPX stereo decoder coils. When I worked on the tuner I didn't have any spares and managed to jury rig the originals to function, but I've since located a parts stereo with undamaged parts (I rather good originals in something like this).