1970s Zenith Console - Troubleshooting

[ThePlague]

Originally Posted by BeamT

While the label says Motorola, the EIA Code 312 is made by Sylvania. Do you see a date code anywhere?

The yoke bracket is secured with double-sided foam tape, probably no longer pliable. I use a plastic spackling knife to gently separate the bracket from the CRT envelope. You will need some double-sided foam tape to re-secure. The plastic yoke cases are also no doubt brittle, baking in place for over 40 years, remove gently.

It would be very interesting to know from the engineers who designed these sets, how long they thought they would last???

Your existing Tripler looks original to me. If its producing 25KV and its not arcing, its doing what it needs to and could outlast everything else. You could pull the screws, look for signs of arcing, and clean underneath. Your replacement divider looks good.

While you have the chassis out, consider replacing:

The boost filter, if you are using SAMS its C270 10uf 300v, this capacitor takes a beating, and can impact the picture quality.

4.7Meg 2w resister from the focus control to ground. I often find these drift, so will the focus, the original is a carbon comp resister.

Happy New Year!

Unfortunately no date code, not that I can find anyway. Its possible that Sylvania was the OEM for Motorola's CRTs.

The bracket on the replacement tube fell right off, but it looks like the Zenith one is going to be a bit more a job. I have some good double sided foam mounting tape that will do. Fingers crossed everything comes off in one piece.. this is a very high hour set.

As for the tripler, the I replaced the divider after the old one was cracked and covered in HV putty. After seeing that, I am suspicious of the tripler, even if it looks fine. I've got it all apart so might as well while its out and keep the SCI as a spare.

I'll take a look at those components and see if I can source some replacements.

Since I had to epoxy the base and repaint it, I figured why not make the set unique. I give you the Golden Sunshine Avanti.

[Electronic M]

It's definitely unique. If I was going to go with a custom period color I think I pick Avocado green though.

[ThePlague]

I looked for a good Avocado green that was gloss and worked for both plastic and wood, but no dice. We had a few favorable days of warm temperature before it goes back to cold so ran with the next best color I could find.

[ThePlague]

Got around to putting the chassis back in and firing it up!

Got snow and then hooked up the function generator and got worried with the crosshatch image. Triple checked all of my connections were correct and finally found the culprit. Turns out I knocked one of my socketed transistors on the Horizontal module out and it was just laying on the chassis. Thankfully it didn't short any connections. Hooked that back in and got horizontal lock.

Lots of adjustments needed, but it works! Tube appears strong. I ended up removing the extra 4.7 MOhm resistor in series from when I installed the new divider to allow the focus to center.

Work done on the chassis: NOS universal tripler, replaced the 10 uF 300V capacitor as previously recommended, cleaned (deoxit + wire brush) all module connections, DeOxit + Fader Lube on all pots, overall clean to get rid of grime.

On to what will no doubt be a lengthy alignment period. Glad it didn't blow up.

[BeamT]

Your new CRT does look strong! A great amount of what you are seeing will clean-up with purity and static convergence. Excellent progress!!

[ThePlague]

Hello all,

Exciting update! Thanks to help from BeamT, the set has come back from the dead. I was working on the convergence and just couldn't get it right. Turns out you need to have a lateral blue magnet, of which my set was missing. BeamT sent one in the mail and it worked great!

This is the first time the set has really been up in running in years. I am currently chasing down a brightness issue with the set.

The problem: Intermittent pulses in brightness. Sometimes whole screen, sometimes brief sections of the screen get brighter. Overall brightness seems to be down. The Plex picture is at max brightness and it can barely pull apart grey from black. Along with this, there has also been some screen jerking in the horizontal direction, usually bottom portion of the screen. Some fluctuations will also occur and can be audible through the speaker. I've recorded a video of the issue, but will have to link it later.

Work Done: I replaced the Horizontal module (9-57) back to the original one in the set (had replaced with NOS). Initially, this brought the brightness back up and it held until power down of the set. Since power cycling, cannot get this to reoccur. I measured the 24V (24V read) and 125V B+ (123V-125V tuned to blank channel, 135-137V tuned to active channel). High Voltage reads dead on 26 kV. No arching or abnormal noises. Percussive maintenance did not reveal and lose or intermittent connections. All pots have been thoroughly cleaned with DeOxit and Faderlube.

Appreciate any ideas on this! Its so close to being finished (until something else thats 50 years old fails).