Zenith flat chassis jail bars

[zeno]

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

[DaveWM]

did we ever cover the horz blanking parts on this?

[zeno]

Originally Posted by DaveWM

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

[colorfixer]

Dare I ask:

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

[Findm-Keepm]

Originally Posted by colorfixer

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]

Originally Posted by zeno

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

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]

down the jail bar rabbit hole we go

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]

Originally Posted by DaveWM

down the jail bar rabbit hole we go

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]

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

[zeno]

Originally Posted by DaveWM

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

[TinCanAlley]

Originally Posted by DaveWM

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.