Zenith flat chassis jail bars
 

A while back someone had this problem & was never solved.
Also had one at the shop years ago but never followed up
on it.
Although its the upright chassis this refers to they are near
identical electricly. From TP-11 training manual

1) lead dress of the wiring between the 22-5001 caps.
2) getting into IF module via the 24V B+. moving the B+
wire to a different point cures it.
3) I also personally think the replacement triplers may be
the cause or other lead dress issues. It would be nice to
see a true virgin set to see the dress of the HV, yoke, CRT
and convergance as the factory made it.

73 Zeno:smoke:

Mine is probably untouched electronically. Why someone took the screws out of the tab wheel though is beyond me as there's nothing wrong with the tuner. I have acquired new safety caps but haven't been able to replace the originals yet.

Once I am able to get at it, what exactly would I need to take pictures of?

I can't remember exactly where the capacitor is located, but I remember a set from when I was servicing those sets that had that problem.

There was an electrolytic capacitor open and just passing your hand around near the IF would change the bars.

I do remember that if the IF cable was unplugged the bars were easier to find with the O-scope.

It's terrible to get Old, nothing works like it did when you were younger.

rrrhre2s

If it hasnt been touched photo the wiring routes of the CRT socket,
HV & focus leads, Yoke & convergance leads. If virgin the should be
held in place by wire ties etc. I always tried to get them back
where they were but most tech go lazy on that. On a Zenith
it usually dont matter but I have seen jail bars on others due to
lead dress..........

73 Zeno:smoke:

Yes, getting old. It sucks BUT you can say almost anything & not get
into a gunfight, they think you just a crazy old fart:yes:

Interesting comment on jail bars, seems almost imposable with all the steel in a Zenith your hand near the IF strip would do that. I will dig
up the old thread & pass it along if he isnt reading this. I know its
not a one time thing, while helping on it I called our old road man.
He had one after he did some other work but the customer didnt
want to go further. Like to know myself as I do want to get a
flat chassis myself someday & knowing my luck it will have jail bars.

73 Zeno

c208, a 5uf, usually a Callins. We replaced all of the Callins caps in Zeniths, as a way to prevent callbacks. 5uf 15 or 25V cap - just look for the black cap with red ends near the IF module.

Good to know. I just remember the NP cap in the video & another in the
AGC that caused snow IIRC. I am not a re-capper but in this case
it would have paid off.

BTW that index was in great shape & much appreciated, will
return the favor when I can........

73 Zeno:smoke:

The old thread
http://www.videokarma.org/showthread.php?p=3081658

I dropped him a PM hopefully this will help him.

73 Zeno:smoke:

Here we go, hopefully everything's in place.

Callins Caps! You had 'em too....?!
 

Thought--as they were Irish made, its only the UK that had these terrible black plastic bomb components...

Thorn UK/BRC (Ferguson, Baird, Ultra etc),sets were full of them. At the age they are now--Replace On Sight!!:thmbsp:

They were suspect 30 years ago, never the best of caps....

Yes, Callins Ticking Time Bombs. Replace them on sight.

Okay, been away for some time now. Basically gave up every fixing the jailbars.

I'm not sure what in this thread I should be doing/checking, so I'll attach pics of the areas I believe are being noted.

I'm attaching pics of the lead dress of the set when I got it. I don't know if it's factory, but I'm also attaching a pic of after the cleaning where I tried to put them all back the way I found them.

I'm also attaching a pic of the safety caps (the 22-5001 mentioned) and the bottom side of the IF module where I believe the 23.4V B+ is located on the 4th pin of the module in the upper left of the section I outlined.

So if there is anything you think I should be doing in any of those areas, please let me know.

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:smoke:

Would those caps be on the top or underside? I recapped the entire chassis, minus the sound board and any in the tuner and remote receiver section.

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.

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:

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:

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,

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.

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

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:

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.