Zenith console
 

ok here is the deal, all tube zenith console. It had a brightener on it, I removed that, rejuv the picture tube and its playing now, decent pic, not the brightest but not bad, needs a mild convergence.

Question, do I start recapping or just leave it be. I has several of the plastic paper caps (the round brown ones) several white ceramic tube caps (1000v) and several electrolytics not counting the cans.

It's playing well but for how long....

it has the service save panel, so I was going to just lay it on its side, leave it all hooked up (no power of course) and start one cap at a time. I belive in do no harm but I also know that these caps are way past expected life.

Also it would be easy to just clip the old cap and pig tail on a new, I know not the prettiest but done neatly it would look fine. This minimizes the lead dress and stress on other parts that share the same mounting point.

Anyway just looking for some opinions, I rarely get a set that works this well to start with of this vintage.

oh and its a 20Y1C38 chassis

a couple screen shots, only thing done was to rejuv the pic (red gun only) and remove the brightener.

and I do have a replacement picture tube, I just have not replaced one before so am a little hesitant to jump on that.

crt looks presentable.save the other one just in case or something else might be in need down the line.as for recapping-my opinion is it couldnt hurt but if it is playing well?the installation is your discretion.i have done this either way and frankly it has worked out well.thats the beauty of this hobby,you can do as you please.i remember back in the experimental days,we would swap out crts just to get a certain look.so many tubes that were discarded because we didnt like the way something was.they were plentiful then.now-they are gold!that set looks good as is!

one thing that is nagging me is if there is a cap that if it fails will do damage to a part the is hard to find. I just check the vert out tube cathode, its not bypassed with a large cap (I was thinking if it started leaking or shorted it could foul up the tube bias and damage the vert out tranny). I am trying to find all those suspect caps to see what they do. Looks like a lot of screen decoupling which other than stressing the power supply does not seem too dangerous.

I dont change the caps on those zeniths until they fail. They are good quality caps. I have 3 sets with that chassis and cant say I have had a cap failure yet. You may have to tweak with the sound coils to get the buzz to a minimum.
Check the cathode current. Should be around 250 but always seems a tad higher like 275.
Check the HV, lowering the HV raises the cathode current and load on the flyback. HV regulation basically is achieved by loading down the 900 volt boost. I have been leaving my sets up around 26-27kv.

Thats good to know (that you have 3 sets with orig caps).

One thing I know it needs is a good tuner cleaning. I may get around to doing that. The UHF is jammed up jelly tight, the vhf needs to be jiggled to get good reception.

That is the same chassis I have on my big zenith console (the French provincal with the nice SS tuner with all the plug in transistors). I have not even tried that one out yet.

Is this a set with the concentric tuning knob? If so, that inner wheel for the UHF swells around the shaft over time and seizes it. You will have to take it apart and carefully hone the hole with a drill bit slightly larger than the hole, or use emery cloth/light sandpaper in a non extreme case. Any forcing of it will strip the gears (if used un-repaired). Apply a light coating of silicone grease to the shaft when reassembling.

yep thats it. I will do as you say.

while futzing with the set I noticed a pretty extreme reverse pin cushion (guess that it the way to describe it, the horz bends up on top and down on the bottom). 1st I checked the tube, checked ok on tube tester, and its new. Next I check the tube pin resistance mearurements to the sams, ok. I tried the pin cushion adj slug and was able to get some of it out but still there.

Its like it just runs out of adjustment ranges. The circuit controlling this has a pretty low parts count. I was next going to try checking to see if it has any plastic/paper caps still in it (the pin cushion circuit). Should prob try a tube substiution just to be sure about that as well.

while fussing endlessly with the convergencem, I decided that something must be wrong. I makes almost no difference when plugged and unplugged (dynamic convergence).

So I decided to check the diode pack, hmm a long crack runs the length of it.

Tested 2 of the diodes, so far both are open. Squeezing the pack makes for momentary resistance readings. I checked the voltages on the conv board before pulling it, no DC reading where there should have been but AC reading instead (which is why I suspected the diode pack).

Anyhoo I have some 1n4005 diodes that I will use (the orig are 1n536).

I hope this does the trick...

That was painless, just snipped out the old diode pack (all were open) left the little bits in but for the ground which i heated up the little solder pot, and pulled out the remnants as I would be having 4 diode ends going in that common ground. I put spagatti on the diodes (color coded) and installed.

Whats nice is now that I have a good diode pack (well after I test it anyway) is I have a set of reading that I can use in circuit to compare other convergence boards with. It will not be fool proof, but hope it finds open or shorted diodes in circuit.

I am getting tired and its dark in the shop as my lighting is not the best so I think I will just bag it for now and reinstall tomorrow. I hope my convergence woes are over.

With out having a lot of experience the problem is knowing when a convergence board is working right, marginal, very weakly.

zenith 17crp4 crt .
 

I have a new in box 17crp4 zenith crt in zenith box if someone needs it.

well it still did not work right, I found the convergence board was missing a jumper, I added that and it worked great, convergence went by the numbers.

after having it on for a while I noticed the vert was a bit jumpy, not rolling but rapid change in size. I cycled the serv-norm switch several times, seems like that cleared it up. will keep an eye on it.

at some point I will have t pull the tuner for a cleaning as it gets snowy now and then. I will try just working the tuner to see if it will self clean, but I am pretty sure its dirty as all get out (based on the dust and general filth of the rest of the set).

Im working on a 20xy1c38 right now and it has almost all the same issues. The most annoying is it acts like the hv regulation is slow. Between different brightness scenes the screen 'bounces'.
It has the pincushion issue and a vert linearity issue about 2 inches down from the top.

Otherwise good picture

yea the pin cushion was the worst it just seems to run out of adj before it gets all of it adj out. there is a RC in the grid circuit of that, not much else that can go wrong. is the pin cushion ok on the bottom? Mine looked ok on the bottom. the Linearity is just a touch off now, only see it in the last 1/2 from the top. I need to touch that up again.

vert is still jumping around, I cycled the norm/serv switch some more, but its still and issue.

there are quite a few coupling caps, a thermistor and various carbon comp resistors in the circuitl. I think I will let in run somemore just to see if use will help it settle down.

Have not tried tapping any tubes yet..

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buzzing, a lot of it that needed constant fiddlling with the buzz pot. it would need to be adj after warming up and even then it was not all that good.

now for some reason after watching it for a few days an hour or two a day the buzz is gone and no longer needs to be touched up.

Geez I wish other stuff would just "get better" like my car....

the volume on this set is still somewhat weak, I am thinking if it has a cathode bypass cap, maybe that is open and its getting too much neg feedback. I have not checked the tubes in the audio so I guess I should start there.

They do get better by running them dont they>?? I still cant figure that one out. The volume is weak on mine too. The buzzing has also got a bit better on mine.
Did you measure you cathode current yet? Mine was 190ma
Post a picture for us?

Great info Andy, thanks! I have run accross those with open resistors.
http://boxcarcabin.com/zenith-Y4520-4.jpg

That is a very fine television apparatus you have there!! I would love to shrink myself small and live in the list!
(At least small enough to disable my wife's soap opera addiction) :)

Thanks! the louvers and off centered crappy channel master crt really bring it all together. The cabinets walls are Masonite, that think dark very hard particle board stuff. Its a bit unique

Ahh, yes, but I too have a Zenith, with a Channel Master CRT. Very off kilter as well. Maybe it's your sets long lost brother? Got it from JPDylon in San Diego a few years back.

thats my set but for a french provincal cabinet. did you see how the convergence board is accessable from the front, under the speaker cover, clever guys those zenith engineers.

pics...

So who's the gal riding with Jim?

Lindey Wagner, think it was the pilot RTV just started over again, the early ones are the best. The pilot had a different Rocky, Noah Berry was much better than the pilot episode rocky.

I like your cabinet better. The extra decorative bulk doesnt do much for me. Most of the later tube zeniths I have seen have the convergence there. I wish they could put the focus in front on these consoles.

yes its a very nice cabinet, very clean, understated and solid wood.

Agree the focus should be upfront. That cab style is prob my favorite, it matches that zenith combo I have. I hope to get on that one next.

I think I will need to clean this tuner it keeps requiring jiggling.

great,great sets!we sold a lot of those back in the mid to late 70s at the shop.always the best picture and the chassis s were bulletproof!love to have one for myself!

the screen brightness flickes somewhat. comes and goes (periods of no flicker the flicer). I assume this could be the HV regulation? or I suppose a dirty pot noisey resistor in the brightness control circuit.

I have tried cycling the brightness control. and the brightness range.

Mine does the same thing. Mostly one scenes with lots of brightness changes and motion.

funny how our two are so much a like. I wonder if a recap would make any changes, I don't really want to since its cool that it has all orig parts and still works so well. I almost think that a recap would simply be putting in cheaply made parts that will not last as long as the remaing life of these old parts.

Not actually knowing what contributes to high voltage instability, my order of attack might be 1) caps in the regulator circuit; 2) high-value resistors in the regulator circuit.

Anybody with experience of what typically causes such flickering, please chime in.

I would like to monitor the HV but think I would need a scope to see if it is the cause. My guess is my analog meter HV prob would be to slow and damped to see it.

I am going to try a few other things, for starters I plan to pull the IF lead form the tuner to get a blank raster. if it still flickers I will put the scope on the crt and check the bias to see if any thing there is going on.

maybe I could use the HV prob in current read mode and use it in series with the scope?

Iv had my fill of this thing. The vertical jitter is the most annoying then there is there is the brightness flicker. Besides those annoyances its got a good picture.
To look at the hv on my scoped, i would put about a 27k resistor in parallel with the scope, connect the ground lead from the probe to the scope then the scope to ground so you are measuring the drop across the 27k resistor using the probe as your high meg series resistance.

Its going back in the barn and then next one is coming in. Maybe the ctc68 or another zenith multi state. I also got that philco roundie i need to get going.

I will keep futzing around with it, if I find out anything I will post.

the vert shakes and the flicker seems to come and go.

I am going to try some tube tapping, and then look into parts around the regulator circuit and the vert. Will also check the pincushion cap on the grid of the pin cushion tube.

on the x1c38 you can pull the regulator tube and it will just go to max, i dont know on the y1c. It typically only floats up a few k so long as the brightness is up.

The regulator works by loading down the 900volt boost, loading down a low voltage winding on the flyback.

Ill pull mine when i get home and see what it does.

just read in the service manual from zenith that jittering vert could be due to a faulty service switch (the one I tried cycling several times) said something about making an "air connections" I assume they mean to just jumper it, also said meter may not see the resistance, therefore the recommedation to "air connect".

there was also talk about a diode/resistor combo to increase convergence range that I may look into (the right side is still just a bit out).

Lastly I think I will check on the cap that is connected to the pincussion coil. No mention of a problem but since its a tuned circuit I was thinking that maybe a out of spec cap may account for the lack of adjustment range, although its more like a lack of amplitude than freq since I can see the center widen to a point but then it starts to shrink back before its completly flat.

I am going to study that pin cushion circuit a few more times to see if I can get my head wrapped around it.