Zenith flat chassis jail bars

[TinCanAlley]

Originally Posted by zeno

Look for small electrolytics in the area of the IF
module. Black & say "Callins" on them.
Cant find my manual so must have sold it.
The 24 V line will use white/brown wiring. Zenith
did a lot of color coding back then.

73 Zeno

Any thoughts on location? I recapped the chassis, minus the modules. Are the caps on a module? If not, I must have replaced them already.

Would be nice to one day watch a space movie with out the jailbars. That's when they stand out the most.

[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

[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.