Zenith 25EC58 Restoration Thread

[vol.2]

jailbars are hard

[TinCanAlley]

Originally Posted by vol.2

jailbars are hard

I finally made some progress.....

I've been calibrating using the Video Essentials DVD and their pluge patterns and their instructions. This has always led to the image being dark on any other DVDs I've used, so I always adjust it. That has always led to jailbars. I decided to search for ways to adjust that differ from theirs. I think I've solved it and with decent results.

I started with contrast mid point. I then brough up brightness until the blacks were crushed and darker areas started turning grey. I then backed it off until blacks were black again. I then brought up the contrast to get a bright enough image. I'm positive this level of contrast is considered in the blooming range, but it has to be. Now all the programs I've tested show no jailbars at all. The image is very watchable, but I would like a little more light in the light areas, but to do so means bringing up the brightness and that crushes the blacks and brings up jailbars. I know it's been a while since I've adjusted and watched an old CRT television, so maybe I'm asking too much for the technology of 1974.

For testing I took my 13" Hitachi from 1981 and adjusted it the way I was the Zenith and I got faint jailbars. Readjusting the new way took them away and gave another very watchable, but not perfect, image.

So either this is a limitation of the technology, or I have an issue in the brightness/contrast circuit. Eitherway, I'm going to leave it be and enjoy it.

I'm now working on removing all the components of my 9-57 horizontal board so I can piggyback the 9-90 horizontal and be able to use a VCR without the waving at the top. I'm also hoping that the board will better center the image horizontally than the current module. It's about 1" or so more to the right than the last one that failed. Not only that, but I hope it solves another horizontal issue I'm having using the original 9-57 module. When the set it started cold, the image is messed up horizontally, but not like before when it was rolling out of sycn. It's a stationary issue and only goes away when I change channels and back, or sometimes on its own after a minute or so.

I wish I had to room for storing more stuff as there's someone near me giving away a 25EC58 chassis and same CRT as mine. Would be nice to have a spare I could use to compare or salvage for parts.

[TinCanAlley]

Well jailbars are gone and all out of spec parts replaced. Set is fully operational and working like a charm. Next is the touch up of paint and painting of stand.

Thanks for everyone's help. This thread is done.

[vol.2]

Originally Posted by TinCanAlley

Well jailbars are gone and all out of spec parts replaced. Set is fully operational and working like a charm. Next is the touch up of paint and painting of stand.

Thanks for everyone's help. This thread is done.

That's awesome. Would like to see some good photos of the finished set though!

Would be cool to see the case and also a decent close up of the video.

[ronl]

[Electronic M]

Which part was causing the jailbars?

This thread started getting too verbose and shotgunny and I tuned out a few pages in.