another zenith combo

[DaveWM]

wondering about how tight the zener diode should hold the voltage, it says 11.5v on the schematic, I get 12.6 at the zener.

[DaveWM]

back to the tv, 23XC36, full raster, but the pic loses about 1 inch from the left side. Its kind of a soft black edge, I am new to this but think I read up on blanking issues. The right side is not a problem. I am going to check the two blanking diodes that connect to the grid of the vertical amp. There is also some streaking in the pic, I need to tap around there but again I am thinking the video driver transistor or more likely the vert amp tube. I am not sure how to check or even test for defective blanking if that is what this is. I dont think its horizonal centering as I assume that would effect the raster. the horz hold adj did not move it at all. I dont recall seeing this when I first got the set, but perhaps I just did not look it over close.

I still need to pull the chassis to go over the HV reg parts and will prob replace the 1kv caps (tube type).

for the streaking I was planning on putting up a test pattern and checking with a scope starting at plate of the video out tube and working my way back, looking for noise. will prob just sub in a new video out tube 1st and hope for the best.

anybody work on one with the loss of pic from the extreme left edge?

[old_coot88]

Originally Posted by DaveWM

...anybody work on one with the loss of pic from the extreme left edge?

Is the raster itself pulling in? Or is there a black bar in the raster? If the former, it can be due to excess HV (the reverse of 'blooming' from low HV). Bill(oc)

[DaveWM]

raster is fine, just when a signal is present the pic pull in from the left about 1 inch, I will get a pic later. I will also try an OTA signal (there are still a few low power uhf stations nearby) just to make sure my converter box is not the problem.

[DaveWM]

I will double check the HV, there is a problem with regulation there and it is a tad high. I "think" I tried a good 6HE5 already and decided I needed to pull the chassis and look elsewhere in the reg circuit.

[DaveWM]

tried it again, HV is about 26-27kv (as low as it will go, have to trouble shoot that some more) the pic would pull in a little as I advance contrast to the max, some scene better that others, if I back contrast down it seems to fill out better. I think I will leave it be until I get the HV sorted out.

[DaveWM]

tried another 6HS5 reg tube, a little better, with HV fully CCW I could just get it to 25kv but that is with normal brightness on the screen, when I turned it down the HV went back up to 27kv. I am sure there is an issue I have just been avoiding pull the chassis, its a real dusty mess.

I left the SS amp on all night (by accident) AM has a lot of rushing sound now between channels. Was not doing that before. I will try again at a differnt time of day to see if I can rule out RFI. I fear that RF transistor may be going bad, in which case I need to figure out whats going on (why the 1st on went and now this one. I can pull it and check on my transistor tester. I should have done that in the 1st place on the replacement to base line it.