Zenith A1512J restoration

[bandersen]

A friend has four or five of these "bug eye" sets and has been very anxious for me to restore them. So much so, he went ahead and pulled the chassis and dropped them off at my doorstep. That's why you'll only see a chassis in the next few pictures. I don't have the CRT or speaker either, but I think I can rig something up.

A couple days ago I decided to tackle one while I wait some parts for my Tandem set. It has a 15A25 chassis and I dug up a schematic in a Beitmans from 1958. Looks like a typical series strung set with a voltage double for B+.


They used little solder "cups" rather than terminal strips. That's a first for me, but I quickly got the hang of them and replaced the dozen or so paper caps.


I pulled the selenium rectifiers out and mounted a terminal strip for new diodes and electrolytics.


There are seven controls mounted facing up which were all very hard to turn. Likely a results of dirt, grim and moisture working there way in. The contrast was so bad I had to resort to a little surgery to free it up.


Time for a power up The proper CRT is a 14XP4 with a 450mA filament. I'm temporarily using a 600mA test 8XP4.

[bandersen]

That got me sound , but no HV.
I powered down the set, did a little poking around and noticed the 17DQ6 HOT was really hot.

The components around the horizontal oscillator seem to be OK. Then, I checked the HOT circuit and found a 100 ohm resistor was measuring almost 200. I'll replace that and see if it makes a difference.

Does anyone have a copy of the Sams for a Zenith 15A25 chassis (388-4) ? The schematic I'm working with has limited voltage info. Thanks!

[marty59]

I had to laugh when you mentioned "solder cups"! This must be a first for you to tackle some Zeniths. While those terminal strips may have been handy on a production line they don't make component replacement all that easy when there's multiples of leads at any one point and nearby wiring. Sometimes I will resort to some "J" hooks to minimize any connection/part damage in those cases. Plus, why heat up a nice solder joint if you don't have to.

They are handy though for exposure to test points on both sides of the chassis!

[tvtimeisfun]

Hello is that the set that has the big handle that folds out from the front so you can carry it??? I have one for sale at my shop that needs tlc pictures hopefully will be posted after turkey day...Timothy

[bandersen]

I obtained a copy of the Sams service info and quickly tracked the problem down to a bad coarse horizontal hold control. I worked on it with some DeOxit and managed to get a small portion of the rotation to conduct.

That got the hor. oscillator running and I have HV. No vertical tough.


Not surprisingly the vertical hold control also appears to be shot except at one extreme.

Mounting all these controls so they face upwards seems to have been a really bad idea


After tweaking the AGC and fine tuning I finally got an image of sorts.


Next up I'll work on those controls some more and try to dig up a 14XP4 CRT.

[bandersen]

I popped open the hor. and vert. controls and confirmed my suspicions. They're a rotted out mess There's plenty of corrosion and the carbon tracks have fallen apart.

Time to go hunting through my junk boxes for replacements.

[bandersen]

I found a couple controls close to the right values and wired them in. That got me a stable raster but the cabinet won't fit unless I cut the shafts down.

[bandersen]

Does anyone know where I can get twist tab panel mount pots like this ? AES only has 250K and 500K, but I need 25K and 750K.

http://www.tubesandmore.com/products/R-V500K-N2

[kvflyer]

Originally Posted by bandersen

Does anyone know where I can get twist tab panel mount pots like this ? AES only has 250K and 500K, but I need 25K and 750K.

http://www.tubesandmore.com/products/R-V500K-N2

Bob,

May be expensive but I would bet that Mark Oppat can make any type of pot that you need.

http://www.oldradioparts.net/

[Kevin Kuehn]

Tried Mark Oppat? http://www.oldradioparts.net/

He can probably make those from NOS parts.

[edit] oops, posted same time as kvflyer.

[dieseljeep]

Originally Posted by bandersen

Does anyone know where I can get twist tab panel mount pots like this ? AES only has 250K and 500K, but I need 25K and 750K.

http://www.tubesandmore.com/products/R-V500K-N2

I would try soldering a control nut on the original pot mounting plate.
Then you can thread on the replacement pot. I've done it before.
Get out the old 200 watt American Beauty.

[bandersen]

Thanks. I'll give Mark a try.

[bandersen]

I finally got my hands on the rest of the set. The CRT turned out to be a headscratcher.

It's been rebuilt and the label indicated 14R/XP4. The 14RP4 is 600mA while the XP4 is 450mA so how could this CRT sub for both ?


I hooked it up to a CRT tester and it does draw 600mA which made me wonder how well it would work in this 450mA series set. Only one way to find out.

So it does work, but I have the brightness control nearly maxed out.


Now for a bigger issue. Serious lack of width. It's only about 50%. The schematic showing something called a "width sleeve" but gives no indication how to adjust it.


This is the first time I've encountered one of these. I assume it's this grounded ring around the neck Moving it around has little if any effect.

Any ideas ?

[Kevin Kuehn]

I've seen some sets that have what looks like one layer of brass shim stock wrapped around the neck. Sliding that in or out of the yoke changes the width. I wonder if that ring originally kept such a sleeve from shifting location?

[IsthmusTV]

My Zenith T1816 bug eye also has a width adjustment sleeve. I was able to vary the width by a combination of rotation and sliding it in and out. But the range of adjustment was relatively small. I don't think that it would be enough to fill out the width in your case.

I just saw Kevin's post. And yes, mine has the wire ring (with a ground wire) over the brass sleeve to hold it in place.

-Clark