Zenith porthole poor width question....

[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,