1970s Zenith Console - Troubleshooting

[ThePlague]

Originally Posted by zeno

The pix is not up to how they looked. I think the CRT is a little weak.
That will make it hard to set up. Cant tell for sure from up here in NH. !

Check a few things.
Boost, 1K resistor on focus pin if CRT, be sure instant on
is working. Also for laffs check the CRT date codes & EIA ## to
see if its OEM. Check diodes on convergence panel.

73 Zeno
LFOD !

Too bad I didn't get this far on it while I was still in CT last year!
I am not sure what you mean by "Boost" but I checked the resistors out when I had the socket apart, all good there. Instant on is working.

I attempted to re-do my purity and I think that helped a bit. I re-seated all of the Semis. The 221-46 Semi on the Chroma Duramodule had two legs fall apart. Thankfully I had a NOS one from another Duramodule and that did the trick.

The CRT is OEM and an AG125VB0P22 (if I read the faded label right) with a date code of 4-13 punched out. Early on I complained of faint letterbox burn in. It never came across in the pictures, but it is certainly there. It wouldn't surprise me that this is a high mileage set. The red gun certainly seems weaker/more orange in comparison to blue and green when turning each color down.

Below are my best shots so far. I'm going to order some convergence strips for the left side. But other than that this may be where the set sits for awhile as I am bit burnt on it.

Is it feasible to source an Chromacolor tube for this unit? I have heard of people who hoard them.

[ThePlague]

I'm 95% I am dealing with a weak CRT. Hopefully I can find someone with a tester near Denver area.

Would replacing the HV tripler help at all? If that HV divider was destroyed its a possibility the tripler took some damage. I am not sure what the symptoms of too low of HV would be though.

[old_tv_nut]

In the earlier picture with crosshatch and circles, the height is way too big. If this is still true, it will affect convergence. Make sure the height is correct before proceeding.

[ThePlague]

Hello all, been awhile!

I've got a good Sylvania 25VAQP22 from ETF sitting in the garage ready for an install. I will begin chassis and picture tube removal in the near future. I will be taking my time and attempting to restore the cabinet at this time as well.

I've located the disassembly instructions in the service manual and it looks more or less straightforward. Does anyone have any tips/tricks/gotchas when doing this kind of work? And with this 25DC56 chassis, are there any items I should touch while the chassis is out of the console? I plan on installing a new voltage tripler given how destroyed the divider was.

[zeno]

Originally Posted by ThePlague

Hello all, been awhile!

I've got a good Sylvania 25VAQP22 from ETF sitting in the garage ready for an install. I will begin chassis and picture tube removal in the near future. I will be taking my time and attempting to restore the cabinet at this time as well.

I've located the disassembly instructions in the service manual and it looks more or less straightforward. Does anyone have any tips/tricks/gotchas when doing this kind of work? And with this 25DC56 chassis, are there any items I should touch while the chassis is out of the console? I plan on installing a new voltage tripler given how destroyed the divider was.

Most sets the CRT comes out as an assy with DGS shield, conv, yoke etc.
Lift out by sides NOT neck. To have grab room put a box a little smaller under the face of CRT. The cabinet will drop away. Move to a table & transfer parts.
Install.
A helper is good, he can lower the cabinet slowly & hold it up to
get the MTG screws started.
Have fun

Zeno

[zeno]

One other thing. Xcelite used to make an extra long 1/4 inch
magnetic nut driver. I would guess its 25" - 30" long. If you can find one its a must for some sets. Also comes in phillips & #10.
I will see if I can find mine & post the model ## for the group.

Zeno

[init4fun]

Originally Posted by ThePlague

Does anyone have any tips/tricks/gotchas when doing this kind of work?

Just one.

Take lots & lots of pics of everything before, and during taking it apart.

[zeno]

Model for driver is Excelite LL-8-M- 1/4
Overall 21" long. Its needed for 19" Zenith hybrids. CRT screws & tuner screws very hard without it.
I have two of them. Cant make up my mind weather to leave each son
one or get buried with one & let them fight over the other !
They are on E-bay sometimes.

Zeno
LFOD !

[ThePlague]

Originally Posted by init4fun

Just one.

Take lots & lots of pics of everything before, and during taking it apart.

Most certainly!!

Originally Posted by zeno

Model for driver is Excelite LL-8-M- 1/4
Overall 21" long. Its needed for 19" Zenith hybrids. CRT screws & tuner screws very hard without it.
I have two of them. Cant make up my mind weather to leave each son
one or get buried with one & let them fight over the other !
They are on E-bay sometimes.

Zeno
LFOD !

Thank you for the tip about the box, sure that will come in handy! I was able to snag a 21" LL-8-M 1/4 on today, its going to save my bacon.

While I was looking around, I figured I should probably get some proper tools. I picked up an B&K HV-40 probe as well.

I am currently looking at NTSC Pattern Generators and I was wondering if you had any recommendations? I am between the B&K 1246 and the Leader LCG-396. I am leaning towards the Leader for the color bar ability, but thought I would ask around before committing.

[zeno]

Look at the Sencore VA48 & VA62 also. We ran them with good
luck. They will do almost everything. Be sure it has BOTH manuals !

Zeno

[ThePlague]

Hello all,

Here for the yearly check-in! Glad to see that Videokarma is back up and running. Was a bit worried all of this thread was lost to the wind. I backed it up manually just in case.

Anyhow, finally had some downtime to get into this set again. Turns out my replacement tube is actually a Motorola MV 25VAQP22. Hopefully it works well, at least it is not a rebuild to my knowledge.

Looks like the Tripler was replaced with a "SCI 212-139" at some point. I still plan on replacing it with my NOS Zenith universal Tripler. I did notice that it has a "focus" lead, but the current setup has the focus running through the divider instead. Unfortunately it did not come with the usual documentation in the box so I am unsure the best way to handle that.

Currently repairing the base with some epoxy and giving it a repaint while I work on the electronics. Fingers crossed the swap goes well.

[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 resecure. 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 exisiting 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!

[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.