new '78 Zenith console

Well, new to me anyway. Got it for our favorite price ZILCH! It's a model 25JC49,Z serial #350566 (might have another digit on the right, hard to see). Built February 1978

Anywho, it works sorta kinda. Here's a run down of the symptoms:

Shuts off with no rhyme or reason, although the on/off button on the control panel as well as the circuit breaker (on the rear) both seem kinda funky. The CB sticks in but will also sort of pop out as well, probably could use a cleaning. The on/off button seems not to have much travel when you push it.....feels like it responds from pressing it sideways as much as actually pushing on it. Just weird.

Then there's the "Master" on/off switch (on the control panel). Not quite sure what to make of this....it will keep the set from being turned on if it's in the off position, but once the set is running and you turn this off the volume level increases!! Not a whole lot, but it is definitely noticeable. What the hoo hah?

While watching a video tape the sound went away....changed channels and fiddled with fine tuning...no difference. Flipped to an on air signal and it was fine. Cycled set on and off only then to find that both picture and sound from VCR (channel 3) were now gone. VCR works fine with other TVs.

When the pic and sound from the VCR were working, I noticed some herringbone pattern to the picture which is absent when watching on air broadcasts.

Tuner seems to have lots of crosstalk...can receive the same station on an additional channel number (IE: channel 8 also comes in on 9 etc)

Small centered band of black at the top of the picture (linearity?) Stays the same size regardless of whether set is cold or been run for a while.

Haven't yet checked if remote works (is an electronic ultrasonic flavor)

Channel indicator light and Color Sentry lights are not illuminated....does this require pulling the chassis to get to these bulbs?

Below is a pic with more to follow. Thanks for any tips etc!

Anthony

Video output board shows darkening of circuit board near the resistor(?) which says "HOT" Is this normal or acceptable?

Bright orange cap on the horizontal power module, is this part of that recall I remember reading about? Apparently there were failures of some cap that lead to major problems like the picture tube's neck melting and shearing off! Anyone know what the hell I'm talking about?

Lastly, I noticed a sticker on the picture tube which indicates that its a 23VCMP22 ....so is this a 25" set or a 23"? The model number of the set leads me to believe that its a 25"


Does anyone have a Sams for this that they want to sell? Would this be considered in the Chromacolor or System 2 family? There don't seem to be any markings on the set to show this. Thanks again.

Anthony

[jstout66]

Nice set Anthony! My brain is a little foggy yet this morning, so I will post more later, but for now..... Your set has the "good" cap which means the service man did the recall procedure. Orange cap is good, white cap is bad. The set IS a Chromacolor 2 chassis. I'm pretty sure with that picture tube number it's a 23" set. Chromacolor's are great sets when working, but have noticed that they either seem to work fine, or have tons of minor problems that take awhile to correct.(there seems to be no in-between) I would start with carefully removing each module and replacing them firmly. Clean the pins if you notice any carbon build-up. In most cases that corrects alot of the problems. The module design is a weak point on this chassis. As for the fine tuning..... Are you tuning each station with the AFC button off? That is the correct way to do it, then when you have the best picture, you should be able to turn the AFC on and be fine. You could also have a bad 75/300 ohm adaptor. I've had that problem before on a few sets. Also, after you try re-installing the modules, if you still have specific symptoms it's pretty cut and dry on which modules will need to be repaired or replaced, just look on the schematic and it will tell you which function they control. I have quite a few NOS modules, so if you want, post a list of the ones your set uses and I will give you any that you may need. OH!! and last.... The module that has the "HOT" section on it. Do NOT get near that one with the set on! You'll get quite a zap.

Thanks for the offer of the modules and all the info! In my dim memory I was thinking that the orange cap was indeed the replacement version, glad that's one less thing to worry about!

Won't be able to dig further into this set until after Christmas at the earliest (is in storage right now)....in the meantime I'll try and locate a Sams for it. Got a line on another color Zenith, 1969 vintage original owner family, also for free!

Anthony

[peverett]

This set is new enought that it may have a high voltage shutdown circuit. If the high voltage get high enough to cause X rays from the CRT, the set shuts down.

Problems in the low voltage supply, the high voltage supply or the shutdown circuit itself can cause this. I found a bad electrolytic cap in the low voltage suppy of an early 1980s Zenith that caused this problem.

Originally Posted by peverett

This set is new enought that it may have a high voltage shutdown circuit. If the high voltage get high enough to cause X rays from the CRT, the set shuts down.

Problems in the low voltage supply, the high voltage supply or the shutdown circuit itself can cause this. I found a bad electrolytic cap in the low voltage suppy of an early 1980s Zenith that caused this problem.

Well I suppose that's possible, but the picture doesn't display any anomalies except for the very short shrinkage (black band at the top. and only in the center third of the screen...maybe about 1" tall) which I think is probably more of an adjustment issue. There is a small module not shown in the picture on the right side (as viewed from the back) which has a relay......I had an 80's Zenith console which developed an intermittent shutdown that was due to such a relay going bad....have heard that this is somewhat common for Zeniths that use this arrangement. Then again, it could be a funky circuit breaker or even the on off switch itself.

When I get a chance, will inventory and identify all the module numbers, clean the chassis, reinstall the modules (check and clean the pins as needed) and then attempt to make whatever adjustments I can. I should be easy to spot when I'm done.....I'll be the guy with the Marty Allen hair-do (who remembers him?) Hello Dare!

Anthony

[Sandy G]

Hey-...Didn't Marty get a new gig as that Beauzeau who runs North Korea ?!?-Sandy G.

[bgadow]

Hey, I just might have a Sams for that thing. (anythings possible) Too cold to go looking out in the shed tonight, but I'll let you know.

All your bases belong to us! (so sayeth diminutive impotent North Korean madman)

[bgadow]

Hmmm...just what DO all these Sams go to? No, I don't got that one, neither. Looks like its in #1744.

Thanks for checking Bryan!

Anthony

[peverett]

The two that I have seen with this issue did not have any problems visible in the picture either. They would just shut off without notice. If the set was unplugged or turned off for an amount of time, they would come back on.

I determined that the high voltage was shutting the set down by lowering the line voltage using a variac and meausing it. It was close to the Sams noted limit at the nominal line voltage. The sets would play forever with a reduced line voltage.

[Eric H]

The vertical shrinkage may adjust out, isn't that the vertical module down in the bottom right corner? the one with the big aluminum heat sink.
Or maybe one of the electrolytic caps is getting tired.

If you only watch letterboxed movies you'll never know the difference