Project impossible? bringing a magnet-box back from the dead?

[Alex KL-1]

Originally Posted by Yamamaya42

Since I lost the chance to get the zenith television, I have decided to pull this project out of the shed and try to toss it together again.

It does work even though the CRT is weak and lacks contrast, but does get a bit better as it has been on a while.
It uses a 6EB8 for the video output / sync sep, looking on the sub chart, it;s said that a 6JT8 is a drop in compatible replacement, and on an audio site I saw... " Plenty of cheap tubes to choose from in that footprint, though - 6GN8, 6HF8, 6AW8 and more. 6LY8 and 6JT8 have more gain in the pentode section,"

And more gain in the pentode section may be just what this tired old CRT needs to limp along for a few more years of light use!

Feeding the CRT with strong signal will definitely helps and is worth but, if the signal surpasses the k-g1 bias (eg. a CRT with 60V cutoff and a 70Vpp signal) will make grid current, and the result is annoying bars at the side of contrasted objects like captions or subtitles, for example. Good to carefully adjusts the contrast.

[Yamamaya42]

https://www.youtube.com/watch?v=PvMHr4-WO8s

New video with the new tube 6JT8, It did make a difference!

[old_tv_nut]

nice

[uncleputz]

I saw this topic just today. I am currently working with a Magnavox Stereo Theater with this same chassis. I'm thinking it is a version of the C36 chassis. They made several different versions of the same chassis. The ones for Stereo Theaters used the 6GC5 audio output tube for a cathode follower, then fed the audio thru the stereo amplifier. My set has the 27ZP4 picture tube, which tested much like this one did, but at least it lights and I have a full raster. The problem I'm currently having is that I have no audio nor video, so I need to try to troubleshoot that. Sams has schematics for the C36 series chassis, but none of them are exact. I hope I can get mine going since I have had the rest of this thing apart as far as I can get it, including the cabinet. I found it in an abandoned house in Detroit that was being torn down. It had a half inch of cigarette scum all over it. Mine has remote control and the whole shot. Top of the line model for 1962. Mine does not have the UHF option.

[Yamamaya42]

Originally Posted by uncleputz

I saw this topic just today. I am currently working with a Magnavox Stereo Theater with this same chassis. I'm thinking it is a version of the C36 chassis. They made several different versions of the same chassis. The ones for Stereo Theaters used the 6GC5 audio output tube for a cathode follower, then fed the audio thru the stereo amplifier. My set has the 27ZP4 picture tube, which tested much like this one did, but at least it lights and I have a full raster. The problem I'm currently having is that I have no audio nor video, so I need to try to troubleshoot that. Sams has schematics for the C36 series chassis, but none of them are exact. I hope I can get mine going since I have had the rest of this thing apart as far as I can get it, including the cabinet. I found it in an abandoned house in Detroit that was being torn down. It had a half inch of cigarette scum all over it. Mine has remote control and the whole shot. Top of the line model for 1962. Mine does not have the UHF option.

From what I can see, the ones set up for audio output via a separate Stereo amp , tap off sound at the plate of V7 before the 6GC5 audio output tube, but still have the 6GC5 in there as a voltage divider for the 120v source, which is critical for the video and audio IF sections, and the tuner, so if there was no 120v, you would have raster only

[uncleputz]

I have a Tolex project on the bench at the moment, and as soon as it is done, I need to get back on this set. It's been awhile since I worked on it, so I need to replace the AGC resistor which has drifted low, then power up and see what I have. I have a set of test/extension sockets, since the tubes in the IF strip are in non-removable shields. I'll do some voltage checks and go from there. My problem is likely from the If strip to the tuner someplace. I hope the tuner doesn't have to come out. What a bear....