zenith table top metal
 

20x1c36

pulled the HOT and the VOT did a slow power up, no issues, but the two lower B+ were non existant. Check the big 17w sand resistor on top, cracked. replaced it with a hollow tube 20w ceramic coated one, tried again but current went high on the metered variac right off, so stopped and checked the B+. 200 ohms on one one of the lower voltage legs, hmmm no wonder that big resistor cracked. traced the B+ around disconnecting here and there, all the way back to the pin cushion adj coil. It was ok so check the other side of the pin cushion, it went to a 6kT8 tube (part of the pic cushion) plate, which was bypassed to the ground with a .0033 blue disck cap.

hmmm this is odd the cap has what looks like a pimple on one side and a divot on the opposite. while watching the meter I squeeze the cap and the meter needle moves a lot. pull the cap and its shorted. replaced cap and B+ resistance goes to about 15k.

another slow start, all good this time current is nil (HOT and VOT still out) and filter caps are stone cold. so after about 1 hour of this slow ramp up, I decide to give it a go. HOT and VOT back in fast power up I hear the HV and then it all comes too life.

Color tint is too magenta, Talking it over Dan he suggest checking the phasing tube a 4 diode tube. Sure enough its weak on on and VERY weak on 3 other. Put a new one it and color is great, with full control of the tint.

while at it I check the other tubes, all test ok, I leave the IF tubes in order as I dont want to mess up the alignment. that pestky pincushion tube has a short in it (hmmm I wonder if there is a relationship in that short and that goofed up disk cap). Its also a burst amp tube so it may have been part of the color problem as well.

The vert is a bit jumpy, and it has a very slow hula on the right side. So I will prob have to pull the chassis and replace those HV tube caps in the vert circuit, and check my grounds. Oh and the tuner/controls need a good cleaning.

yikes on the third pic, thought I would upgrade that one

Anything that ugly has to be running for public office....

Nice set and a lucky score. A friend of mine has been looking for one of those for a long long time.

This is the kind of set I remembered as a young guy. I watched my first episode of Laugh In over at a friends, on a Zenith that looked a lot like this!

yep, I remember having one as a teen, my own color tv, that was a big deal back in the day.

I thought the CRT was cloudy (besides the green halo) turns out it was just filth on the top of the screen, a little alcohol took care of that.

Last nite it did something odd, screen started to fade from the edges and get darker over all. turned it off, for a few minutes, then tried again, all good.

That was odd. I will mess with it some more if it does it again I will start looking around. could be something as simple as a heater filament. I have not done a thing to this one besides that shorted cap in the pin cushion, so I would not be surprized if there is a dirty tube socket somewhere.

long term update. been watching MEtv, last night all of a sudden gets very contrasty... 1st check was the video amp tube, subbed, no change, next up was the AGC tube, a multfuction compactron, again no change. So I go to the AGC and reset it. Ok now I get the pic back but its VERY VERY touchy on the AGC either snow or blacked out and no sync over a range of only a few degrees...

Flip the TV on its side, remove the service saver bottom, start with a shot of tuner cleaner on the agc pot (the set has a lot of dirty pots). No real help.

Jumped a .15 AGC filter cap, no change, jumped the 4uf cathode bypass, bingo normal AGC. I replaced it by doing some pig tails on the new cap, atttaching to the cliped lead from the old. For fun I put the old cap on the cap tester, nada, wide open. This is one of the little tube electro used in zeniths, black body with a red end. The set is all orig but for the disc cap in te pic cushion and now this little electro. I know I could have avoided it by just shot gunning the whole set, but I enjoy finding problems and learning symptoms and fixes. So next time I run into a hyper critical AGC you can bet I will be checking the cathode bypass on the sync tube 1st.

The set still has a tint issue fully CCW is purple, but when CW rather than green the color just seems to say about corrent for tint but weaker. Fortunity the tint is fine, that is I dont need more green, but there is something wrong. I did notice I could get the green to work somewhat when the set was tilted up on its side (when I was checking for the AGC issue) Thats odd. Not sure why having it on its side would effect the tint control, unless just the flexing of the chassis or wire harness that connect the tint to the chassis had some corrosion where the plug harness connects up. Not going to deal with that for now. got to get the shop cleaned up.

while watching TZ, the pic starts to shrink horz.. turn off, nothing seems hot.

tilt out the cage, pull the reg and hot and put them both on the tester, both test weak. Grab a couple pulls that test much better, turn on all good again.

I will have to do an extended watch before willing to say all good. I can see why all those do it yourself tube testers and tubes were at every corner drug store and 7/11 back in the day.

I think this set is just going thru its next few stages of weeding out parts that have been idle for 40 yrs.

I had a major horizontal shrink on my 1971 Zenith hybrid. I turned it off let it cool for a while turned it back on several minutes later and it was good. The problem has not returned in the two or so years since then, and I have no clue what caused it.

Tom C.

Dave - those black "Callins" electrolytics are the bane of Zeniths. We'd always change those regardless of condition. Doing this saved us a ton of callbacks on heavy Zenith sets. Doug H (DRH4683) can comment on this as well, as he has replaced quite a few bad Callins caps.

Those Callins caps were dumped by Zenith and bought up by surplus outfits. I've got a PolyPak assortment of caps - all Callins, all leaky, low value, or both.


Cheers,

Roger that, I will be replacing them all soon.

Thanks for updating that third pic. Yikes!! Scary

whats kinda nice is there is only 2 cans, the rest (7) are single units. The cans are a 3 and 4 section, all 475v

my 72' Z had low HV which cause a pulled-in horiz deflection.