Zenith Chromacolor console no video

[StratLou]

Hello guys,

My Mom's early 70's Zenith Chromacolor console is having an issue for the first time since the 80's. Not sure how to find out what model it is. I know she should probably get a new one, but:

1) The old console has sentimental value.
2) She uses it maybe twice a year (for "special occasions") and this is not her main tv.
2) It actually may be more costly to replace rather than fix the Zenith, depending on what's wrong with it (why I'm here for help).

The last time it was on (at least 2 or 3 years ago), all was well. Turned it on the other day and found the audio was fine, but the picture tube was black. No static electron feel when I put my hand on the front of the picture tube so no beam. I removed the back cover and found that there is the orange glow at the back of the picture tube showing the tube is receiving current. I'm hoping that since the end of picture tube is glowing that maybe there could be something else causing the problem.
Does anyone have any info idea what the problem could be and what it would need to be repaired including some thought on cost. Needless to say, if the picture tube is gone, it probably would be cost prohibitive but we'ld like to try to save it. Photos below:







Thanks very much.

Lou

[sampson159]

no high voltage.check fuses,tripler,hot,etc.this zenith is a keeper and in my opinion,the best set ever manufactured.i have been searching over 10 years for one of these.good luck,keep us informed!

[bgadow]

Although not highly valuable, this is maybe the best built color tv that has ever been made. I'm not well-versed in the repair of this chassis, but others on here are. Picture tube is way down the list of things this is likely to be. Probably one bad component in the HV circuit.

[radiotvnut]

Having a schematic would be a big help to you. The first thing to do is make sure that the horizontal output stage is getting B+ voltage. In the newer vertical chassis sets, there is a big 10 watt wirewound resistor that will open and kill the HV. I believe the older flat chassis sets like this one have the same resistor. If there is B+ voltage, check that the horizontal driver module is producing a drive signal and receiving the porper B+ voltage. Also, check the horizontal driver transformer that couples the drive signal from the horizontal driver module to the base of the horizontal output transistor. I have seen these transformers open. If all the above is good, carefully unsolder the lead from the tripler that goes back to the flyback transformer. With this lead moved so it can't arc to the chassis, power up the set and see if you can draw an arc from the lead to a screwdriver. If you get an arc; but, have no HV at the CRT second anode, you have a bad HV tripler. When these triplers fail, they generally either arc/burn or short and blow the fuse/trip the circuit breaker. In some cases, they can fail silently and kill the HV. Be careful in that if the tripler shorts and the TV is left on, the flyback transformer and horizontal output transistor will be ruined. I've seen it happen many times on the vertical chassis sets on once or twice on the sets like what you have.

[StratLou]

Thanks for the responses! It's nice to hear that some of us still have respect for the older technologies. I have a friend who repairs electronics but lives some distance away. I will try to get him to help me troubleshoot over the phone based on the recommendations. He actually mentioned the possibility of the high voltage being the issue when we spoke of this recently. I have working knowledge of and know my way around guitar amps but not tv's so I may ask what seem to be simple questions for you guys but complicated for me.
Sampson, is there a step by step anywhere that you know of that could guide me through the evaluation of the components you mentioned?
Radiotvnut,
1) You mention having a schematic would be helpful. Is the schematic that I show in the photo the one to help me diagnose the problem or are their others? The one in the pic I posted is attahced to the inside wall of the tv.
2) Can you point out to me, in the picture I posted, where the components you mentioned are located roughly? Would more photos be helpful?
3) Where would the model# be if I need to find more schematics.
4) Regarding the 10W reistor you mention checking if it's open. Would I be able to see that visually or is it something internal that would need to be measured.
5) You also mentioned if the tripler shorts and the tv is left on that the flyback tranny and HO resistor will be ruined. Did you mean as part of the testing procedure you outlined or now as part of the problem, because we have left it on for a minutes when we were evaluating the problem.
I can clarify further if any of my questions are not clear. Thank you guys again for your help. Your info is invaluable and hope it helps to save this set. Hope you guys can help walk me through this and I will try to confer with my friend to some extent if he's available when I get stuck.

[lnx64]

The paper you show is more of a diagram than a schematic. Schematics show how everything is actually wired up together.

[Gunslinger]

those sets were noted for bad service swictches

[StratLou]

Well, who is probably one of the last of the great tv repairmen in the Boston area examined the set today using only a long screwdriver and tapping around (it was hard to see where exactly, but definitely on the right side of the chassis as viewed from the back of the set) the chassis and his diagnosis from this was that the flyback transformer and the output trasistor were gone. He said he could attempt to search for the parts (but felt it would be difficult to find these) but instead discouraged us from repairing the set. He felt that even if these were the only components involved (he felt the yoke could also be involved but no way of knowing until the HV is returned and even then, the picture may still not be that great), it still is a 40 year old set that could have something else go at any time. I felt he was honest as he could've easily said to fix it and charge us a fortune.
What do you guys think of all this and do you have any other thoughts? Thank you again in our attempts to decide where to go next with this.

Lou

[sampson159]

gone as defective or gone as missing?there are clearly in the pictures.rare to see a flyback bad in these sets.hot yes,but flyback,no.possible though.more like a tripler issue.hope you find the parts and get this one going again.as i said before,the best set ever manufactured.period

[truetone36]

I have one of these that developed the same trouble as your set. My trouble turned out to be a bad HOT. There or the tripler is most likely the issue here as a flyback failure is rare in these sets.

[radiotvnut]

The only one of those sets that I've seen with a bad flyback was due to a shorted tripler. When the flyback shorts in these, the circuit breaker will trip within a few seconds of turning it on. The flyback could be bad; or, the technician could have simply told you it was bad. It's not unheard of for technicians to claim that a major part is defective when they really don't want to fix the TV to begin with.

What actually happens is the HV tripler shorts; which, draws too much current through the flyback. As a result, the flyback overheats and shorts; which, shorts out the horizontal output transistor. If you pull the HV input lead from the tripler and replace the HOT, the set will come on and you may get a little HV coming out of the flyback; but, the flyback will become warm to the touch and trip the circuit breaker on the rear of the set.

[Geoff Bourquin]

Good memories of the days when I worked on those. Haven't seen one around here for years.
The yoke is an easy check...a yoke ringer will send test pulses into it, and if the pulse continues to "ring" for a little while the yoke is almost certainly good. I think just about any TV shop that worked on CRT sets has one. I don't remember ever seeing a bad yoke on one of those. I do remember replacing lots of triplers though. I think this set also has a square focus resistor behind the tripler. I replaced a lot of those too, but they usually cracked open and hissed and snapped up a storm.
Did the repairman use a high voltage meter to see what was going to the picture tube?

[bgadow]

If you have trouble finding parts, get the Zenith part numbers and post them here. One of us can probably help. I know I have a nice size box of triplers.

[sampson159]

this had a separate focus "stick".i remember replacing with a focus block from philco sets in a pinch.also use a 556 tripler to eliminate the stick.radiotvnut is right on the money on this one.that set is worth saving!we will help you get parts.

[radiotvnut]

I'll add that it takes a little more than tapping around on the chassis with a screwdriver to determine if the flyback, HOT, and/or tripler are defective. These parts would have to be disconnected and tested with the proper test equipment to determine if they're good or not. The only good from tapping around with a screwdriver would be to find an intermittent electrical connection on the chassis.