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-   -   Zenith Hybrid Low HV (http://www.videokarma.org/showthread.php?t=275094)

Jon1967us 07-01-2022 10:19 PM

Pin 5, V3 again. Yeah, that's why I posted it. It looked a little odd.
I've checked all the resistors in that section and all are decently within acceptable range. All the caps in the H area are all ceramics, except for one C124, which is an Elmenco wax/ceramic. Although cosmetically it looks fine, it's in the crosshairs next time I crack this set open. This one is easy to access. The other White ceramic in the boost, a .1 1KV is only accessible by pulling the chassis, which I'm understandably not enthused about.

I have checked out DRH's post. I referenced it before, for VDR issue in an older metal cab Zenith. The part numbers in this unit, unfortunately were not covered by his cross reference. Although I did try swapping with what I had on hand, it only made things worse. I have no specs for the ones in this set, other than black and orange bands.

Quote:

Originally Posted by zeno (Post 3242640)
Yes Mr Squirrel has some good points as always.
First wave form looks good, assume its at hoz osc.
On your post #11 where was that taken ? . It looks kinda shabby.
So probably concentrate on the HO G-1 drive for now.
BTW drh4683 did a great job on the older chassii VDR. He found
modern subs for them. Trouble was even the newest sealed OEM
VDR's were going bad in the pkg. Do some searching for the
post. It was within the last 2 yrs IIRC.

Zeno


Username1 07-03-2022 11:53 AM

So I looked at this page on a different computer, and it got pictures. I can see the
snippets of Schematics, & the Oscilloscope trace pic. The Scope trace looks very
good. The 190V on pin 11 is high, and at this point I would be wondering about
the 1W & 7W resistors attached to it, and what goes on down stream of that
point. The difference between -78 & -48 on pin 5 is also quite high. I Also
think it's worth taking a current reading off pin 11 as they give a 20ma.
number there..... You know if they print that, it's for a reason, and I
would want to know what it is given the set looks pretty good.
With 30V lower G1 & what looks like a perfect waveform, I
think the picture should be pretty narrow & Boost much
lower (more than 100V lower)..... With a good G1
Drive Waveform, I think I would take a walk on
over to pin 11 and poke around a bit.....

.


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