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-   Solid State CRT Televisions (http://www.videokarma.org/forumdisplay.php?f=184)
-   -   Zenith flat chassis jail bars (http://www.videokarma.org/showthread.php?t=263019)

zeno 03-15-2015 06:20 PM

The cap will be under the chassis in the hand wired part.
It is NOT on a module.
Did you also recap the modules ? I dont remember if
we covered that in the old thread. Also see findm keepms
post.
Sure like to see this one fixed. It worked once & can work agn !

73 Zeno:smoke:

DaveWM 03-15-2015 06:38 PM

did we ever cover the horz blanking parts on this?

zeno 03-15-2015 07:14 PM

Quote:

Originally Posted by DaveWM (Post 3128984)
did we ever cover the horz blanking parts on this?

Yes twas covered. Went through a lot of tests & many parts replaced.
He did everything right, even showed on his scope. Tried grounding
out stages etc. Just wish I had it at the old shop with bright
lights & lots of test equipment, parts etc...........

73 Zeno:smoke:

colorfixer 03-15-2015 10:03 PM

Dare I ask:

On the photos, Zenith ran the HV from the flyback, to the anode, then a lead back.... why?

Findm-Keepm 03-15-2015 10:47 PM

Quote:

Originally Posted by colorfixer (Post 3129001)
Dare I ask:

On the photos, Zenith ran the HV from the flyback, to the anode, then a lead back.... why?

The second lead goes to the focus divider - a resistor pack that divides up the HV for focus voltage for the CRT. The "9894/9895" divider IIRC - we used either the 63-9894 or 63-9895 dividers in Zeniths. Some were the "rocket ship" white-cylinder originals or the beige plastic "matchbox with leads" style. Same purpose/function. later, they incorporated the focus divider in the tripler, and later the IHVTs in some sets.

Cheers,

TinCanAlley 03-23-2015 11:58 AM

Quote:

Originally Posted by zeno (Post 3128982)
The cap will be under the chassis in the hand wired part.
It is NOT on a module.
Did you also recap the modules ? I dont remember if
we covered that in the old thread. Also see findm keepms
post.
Sure like to see this one fixed. It worked once & can work agn !

73 Zeno:smoke:

Didn't recap the modules, but did replace a few with NOS to see if it had any affect. None did.

I am about to refocus my efforts on the ABL circuit. It is the one circuit I got a very strong ringing on the scope and it seems a logical source for the jailbars. I have replacement resistors as one has a brown blotch on it and I don't know if that's a defect in appearance only.

DaveWM 03-23-2015 03:31 PM

down the jail bar rabbit hole we go :D

did you scope the 23.5v source for horz noise.

there is a 47uf cap on the ABL collector that seems like it would filter out.

there is a zener in that circuit too.

TinCanAlley 03-26-2015 04:49 PM

Quote:

Originally Posted by DaveWM (Post 3129579)
down the jail bar rabbit hole we go :D

did you scope the 23.5v source for horz noise.

there is a 47uf cap on the ABL collector that seems like it would filter out.

there is a zener in that circuit too.

I am trying to find all my scope pics, but I'm sure I did the 23.5.

There is a 50uf on the collector of the ABL and it was replaced during the recap.

The scope results of the ABL shows ringing on all leads E,B and C.

http://videokarma.org/showthread.php?t=259533

DaveWM 03-26-2015 07:03 PM

hmmm, I would be real tempted to try and disable that ABL.

zeno 03-26-2015 08:49 PM

Quote:

Originally Posted by DaveWM (Post 3129812)
hmmm, I would be real tempted to try and disable that ABL.

I think we did that too ! I will look at the Sams & see if I can spot
the black caps in the photos.

73 Zeno:smoke:

TinCanAlley 04-11-2015 12:48 AM

Quote:

Originally Posted by DaveWM (Post 3129812)
hmmm, I would be real tempted to try and disable that ABL.

I think we grounded one of the legs of the ABL transistor and it had no affect on the bars. I don't know if that really disables it, or if it just lowers it.


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