Zenith porthole poor width question....

[Kamakiri]

As shown, this is about all the width I can get out of this 12" Zenith porthole.

This morning, I heard about a trick. Apparently if you put a hv disc style cap across the damper tube it will increase picture width. Has anyone heard of this and knows the specifics?

[Findm-Keepm]

Yes, they used to make a Damper width "cookie" - just plug the damper tube into the cookie, then into the set. In the cookie was just a low-pF cap, around 100pf or so.

I still have a NOS one, from Workman (before they were Workman, they were Dunwell)

http://www.videokarma.org/showpost.p...5&postcount=10

Yours for 5 bucks, postage included.

Cheers,

[old_coot88]

I've done this numerous times. But there's a caveat. It's always been on the standard layout with the damper in series with the B+ line going to the flyback.
I never did it on a pre-standardization layout where the damper is not in series. Your porthole is probably pre-standardization, so it might not work. Probably wouldn't hurt to try, though.

Try a disc cap of around 47pf - 82pf @4KV.

A quick check of the schematic will tell if it's a series layout or not.

(EDIT.) Have you checked the G2 (screengrid) voltage on the H out tube? If it's low it'll cause reduced width and HV.

[Findm-Keepm]

Originally Posted by old_coot88

I've done this numerous times. But there's a caveat. It's always been on the standard layout with the damper in series with the B+ line going to the flyback.
I never did it on a pre-standardization layout where the damper is not in series. Your porthole is probably pre-standardization, so it might not work. Probably wouldn't hurt to try, though.

Try a disc cap of around 47pf - 82pf @4KV.

A quick check of the schematic will tell if it's a series layout or not.

(EDIT.) Have you checked the G2 (screengrid) voltage on the H out tube? If it's low it'll cause reduced width and HV.

Tim,

In your package, along with the cookie, is a bag with some 4KV caps - 100, 130, 160 and 220pf - I was gonna send a PM about them but saw this. I remember we used a 100pf cap in some sets, but I couldn't remember the range of values, and it is probably 47-100pF, so I erred on the wrong (high)side. Hopefully all you need is the cookie.

I see the flyback has been changed. FLy 52 and 53 (thordarson spec'd two flys for the PH's, not sure of Merit or Ram) are different animals, and it wouldn't be the first time someone (not you) changed a Flyback and used the wrong replacement. I have - on a Sony multi-system, and horizontal linearity was off - I adjusted to get it normal, and then had reduced width. So I called Sony, and they confirmed that I had the wrong fly, my mistake, and costly at that. Thankfully the set belonged to a good friend, so I didn't mind the lesson.

On a side, the ETF museum has two flys for Zenith PH's listed on their website...

Cheers,

[bigaudioal]

Originally Posted by Findm-Keepm

Tim,

In your package, along with the cookie, is a bag with some 4KV caps - 100, 130, 160 and 220pf - I was gonna send a PM about them but saw this. I remember we used a 100pf cap in some sets, but I couldn't remember the range of values, and it is probably 47-100pF, so I erred on the wrong (high)side. Hopefully all you need is the cookie.

Has the fly ever been changed? FLy 52 and 53 (thordarson spec'd flys for the PH's) are different animals, and it wouldn't be the first time someone (not you) changed a Flyback and used the wrong replacement. I have - on a Sony multi-system, and horizontal linearity was off - I adjusted to get it normal, and then had reduced width. So I called Sony, and they confirmed that I had the wrong fly, my mistake, and costly at that. Thankfully the set belonged to a good friend, so I didn't mind the lesson.

Cheers,

Fly was replaced with a Merit HVO-11, which listed this chassis (23G22) in it's literature that was in the box with it as an exact replacement.

[Findm-Keepm]

Originally Posted by bigaudioal

Fly was replaced with a Merit HVO-11, which listed this chassis (23G22) in it's literature that was in the box with it as an exact replacement.

What was the original Zenith Fly? It'll start with an "S" - most of the Portholes used the Merit HVO-53, with some windings not used on some models.

[vts1134]

Originally Posted by Findm-Keepm

Yes, they used to make a Damper width "cookie" - just plug the damper tube into the cookie, then into the set. In the cookie was just a low-pF cap, around 100pf or so.

I still have a NOS one, from Workman (before they were Workman, they were Dunwell)

http://www.videokarma.org/showpost.p...5&postcount=10

Yours for 5 bucks, postage included.

Cheers,

Do you happen to have any more of these?

[Findm-Keepm]

Originally Posted by vts1134

Do you happen to have any more of these?

Unfortunately, no. The cookie places a cap of undetermined pf value across two pins of the damper - easy to do without it.

Cheers,

[John Marinello]

A small cap across the width coil will help also, but I agree with the others, there's something you're overlooking.

[vts1134]

Originally Posted by Findm-Keepm

Unfortunately, no. The cookie places a cap of undetermined pf value across two pins of the damper - easy to do without it.

Cheers,

Forgive my ignorance but what two pins and why does that work?

[Findm-Keepm]

Originally Posted by vts1134

Forgive my ignorance but what two pins and why does that work?

Me thinks 3 and 5 - look at the picture - the bottom two pins (holes on the "cookie") are the two pins. I'm not sure, and also not sure of the capacitance, but 47-100pF has been suggested. I mailed it to Tim un-opened, so I didn't have a chance to measure it with my LC Meter. The cap is actually in the little tab that sticks up from the bottom.

Edit: 3 and 5 are the plate and cathode, so it makes sense.

Edit 2: Looking at the schematic, there is a 56pf cap in the yoke. As the yoke was replaced, it may not have the correct values in the yoke, making the cookie do the job of the missing/too low of value cap in the yoke....



Cheers,

[Kamakiri]

Originally Posted by Findm-Keepm

Yes, they used to make a Damper width "cookie" - just plug the damper tube into the cookie, then into the set. In the cookie was just a low-pF cap, around 100pf or so.

I still have a NOS one, from Workman (before they were Workman, they were Dunwell)

http://www.videokarma.org/showpost.p...5&postcount=10

Yours for 5 bucks, postage included.

Cheers,

Well, thanks to the cookie, I now have full width!!!

Picture's off center, but at least it's a full picture!

[Findm-Keepm]

Originally Posted by Kamakiri

Well, thanks to the cookie, I now have full width!!!

Picture's off center, but at least it's a full picture!

Cool! I am Portholio.......sorry Beavis.....

[old_coot88]

Hey cool! That answers sumpthin' I've wondered about for very a long time-- whether or not the damper cap trick will work in a pre-standardization setup (i.e., where the damper is not directly in series with the B+ line to the flyback).

[Kamakiri]

PM sent!