Zenith console - Videokarma.org TV - Video

DaveWM · #1 05-23-2010, 06:04 PM

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.

DaveWM · #2 05-23-2010, 06:17 PM

oh and its a 20Y1C38 chassis

DaveWM · #3 05-23-2010, 06:33 PM

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.

sampson159 · #4 05-23-2010, 06:56 PM

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!

DaveWM · #5 05-23-2010, 07:05 PM

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.

ctc17 · #6 05-23-2010, 08:12 PM

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.

DaveWM · #7 05-23-2010, 08:37 PM

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.

*zenithfan1* · #8 05-23-2010, 08:46 PM

Quote:

Originally Posted by DaveWM

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

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.

DaveWM · #9 05-23-2010, 08:51 PM

yep thats it. I will do as you say.

DaveWM · #10 05-27-2010, 12:33 PM

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.

DaveWM · #11 05-31-2010, 05:37 PM

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...

DaveWM · #12 05-31-2010, 06:47 PM

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.

tvdude1 · #13 06-01-2010, 06:08 AM

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

DaveWM · #14 06-01-2010, 09:07 PM

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.

DaveWM · #15 06-08-2010, 09:28 PM

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).