Should i bother restoring a zenith?

[kramden66]

picture of the channel selector please

[Electronic M]

If the plastic forms are of the same dimensions you could always get his coil remove the wire from it and rewind your wire onto a good form...It takes patience, but if the wire is thick enough the risk of botching it becomes low.

[Tubejunke]

Originally Posted by kramden66

picture of the channel selector please

I will get one a.s.a.p. I am fairly certain that the same one was used for several years.

[Tubejunke]

Originally Posted by Electronic M

If the plastic forms are of the same dimensions you could always get his coil remove the wire from it and rewind your wire onto a good form...It takes patience, but if the wire is thick enough the risk of botching it becomes low.

I assume that there is an adjustable iron core to think about, but either way it goes I don't have any other forms. I am pretty certain that I can order one.

[Tubejunke]

OK, I have an efficiency coil on the way! These things are going like hotcakes to somebody and from the standpoint of a retail purchase of an N.O.S. replacement, there seems to have been FOUR of these in the WWWorld! Wow! Moyer had two about a month ago and had quoted me so in an email. Thinking that I am probably the only person on Earth knocking at a supplier's door for obsolete beyond obsolete TV parts, I didn't react immediately. Should have because they are sold out! I'm thinking that these coils sat around in inventory limbo as long as I have been alive and then sold out two units in a matter of weeks. Interesting to say the least.

At any rate, someone gave me a link to another supplier who just happened to have two as well, but for $13 more. I figured I better jump on in this time or else I may never get this Zenith going due to wishy washy H.O. cathode current. So, as long as U.P.S. doesn't fail me I am good. Frankly, the guy on the phone at this place didn't seem like he cared at all if he sold something or not. Yeah, one of THOSE inside sales guys! Supposedly they no longer really sell to private citizens, so I was sort of out of line even asking to buy their product and have it sent to my house. or that's the feeling I got. He asked me about 3 times what company I worked for. Geez! I kept saying that I work for a company and I am an electronics tech for that company, but I am not buying the part for my employer. So anyway, he finally took my credit card and shipping info. He never read it back to me to insure accuracy, so I hope that works out. Sorry folks, I didn't mean to go on a rant. I am actually happy to announce progress on the Zenith. However, I did a stint once as Inside Sales for an electronics repair/supply place and we were trained to be polite, AND reassure the successful execution of the order through relaying back all of the key data. On the flip, you get a lot of tards most particularly in "parts" related sales. It's sort of the nature of the beast I have learned as I also did auto parts once which is a road that I don't even want to begin to go down here.

So, I throw in the coil and hopefully the crystal replacement for the color will work. That info is in some other thread that I wish that I could locate. I have a bag of common value orange drop caps which I hope will cover many of what I will run into. Might as well replace whatever is left, but I will probably keep the electrolytics. I'm not going to do a play by play with pics and all, but I will definitely try to throw in a few.

I thought about going and picking up that vintage RCA color bar, dot, crosshatch generator that is sitting at the antique mall for another $35, but supposedly you can get DVDs with everything needed for alignment which would be a lot easier. I love old test equipment which A. is necessary and B. is working. Can't say I would ever use old color TV equipment again as I prefer old black and white sets. So the DVD sounds like a plan!

[kramden66]

I have an RCA generator that I think all it needs are the electrolytics , it seems to work but I have a newer b&k that's less then half the size and does the same things as the rca , I was hoping the rca had better color bars but its just like the b&k , neither produces the crosshatch and dots at the same time which is also a little disappointing , it does come in handy , I even use the crosshatch on black and white sets to get an idea of the linearity.

still no picture of the knob

mike

[Tubejunke]

Originally Posted by kramden66

still no picture of the knob

mike

Sorry Mike, no picture yet. It's not a really big thing and as a matter of fact I took the knob that I have and a piece of scotch brite and it cleaned up rather well. I was surprised frankly! Now the little door that covers the controls is a different story. Mine has a few small dents and dings in it that are not going to come out. I would really like to replace that! Do you think you might have one of those if I could provide a picture?

And to everyone else looking at this thread, I got my "horizontal efficiency" coil in the mail the other day. Nice, solid N.O.S. Thordarson part. I need to get specifics on the setting of the coil which supposedly effects the horizontal output tube's cathode current. In another thread this is being discussed as far as running a remote test point for regular checks on what is supposedly a critical measurement on these early color sets. I recommended putting in a fuse holder to have the circuit protected AND as a breaking point to put an amp meter in series to make the measurement.

We (I) need to get specifics on what current measurement would be acceptable on my Zentih and figure out a good fuse size based on that. I hope to find that there is a more or less general fuse size that would work on most early color sets so that I can relay this information to others, or they will find it in this or the other thread.

[Tubejunke]

I got the horizontal efficiency coil in the mail, but haven't started the project of putting it in yet. I am wondering if there is a way that I can install the coil and have it pre-set if you will, so that the current on the horizontal output tube is not crazy high. I guess I can go through getting a amp meter hooked into the cathode circuit which is evidently what needs to be done anyway to make sure that it's not too high.

But I read in another post someone saying that you want to get the current as low as possible and still have good linearity. With that being said, you would think that you could simply run a set and turn the coil down until you start to see the picture distort and then go slightly back up just to the point of having a correct looking picture. If this were correct it would be a heck of a time saver. Not to sound lazy, but I want to get the set up and running to get a better evaluation of what is going on with it, or not.

I do eventually want to put a fuse in the horizontal output circuit and that would give me a perfect place to put a meter in series with the circuit, but that's a bit down the road. Main thing is I don't want to throw this coil in and be instant red plating.

[Electronic M]

In my experience the correlation between horizontal image linearity and HO Tube cathode current is very weak at best on roundy color sets. When performing the adjustment I have not seen any change in linearity while adjusting current from previous tech's setting to the setting that would yield minimum current, but I have read that good linearity and current can be in conflict in sam's folders for some of my sets.

My advice would be to monitor the cathode current on the first power up after the change and as soon as it starts to stabilize adjust the lin coil for minimum current.
I would look at the slug position of the old coil and try to roughly achieve that in the new coil before power up.

Under a minute of redplating should not damage anything(it is when the fly begins to heat up that bad things happen). But I doubt the lin coil could produce redplating unless there were serious circuit problems.

[old_coot88]

If you seriously do not have a meter, there's a 'quick & dirty' way of dipping the efficiency coil. Connect a #44 bulb (which is rated at 250 ma) in series with either the plate or the cathode. Adjust the eff. coil for minimum brightness. The bulb should glow at signifigantly less than full brightness, indicating the current to be well below 250 ma., and in the "safe" range.

We used to carry a 'magic light bulb' adapter in the tube caddy for this purpose; just clip it in the plate lead of the tube. It was surprizing how many sets in the field were 'off the dip'. In the shop we always used a proper (analog) meter.

There was never any observable correlation between eff. coil setting and linearity.

Red plating of the tube should be avoided at all cost. It can kill the tube quicker than it can kill the flyback due to the tube's small thermal mass. I've seen HO tubes with holes melted thru the glass and the flyback was still good.

[Tubejunke]

Thanks Electonic M and old coot88 for the ideas. I guess I know the right way to do such a job, but often there are 'tricks of the trade' that are guicker and/or easier, while being just as effective. I think old coot88's tip is one of those very ideas, for those without a meter at least, but like a meter the circuit still must be broken and the bulb wired in series.

As for me, I have one of the monolythic Hickok Model 209A "volt-ohm-milliammeters, which is primarily for show since I can't find the proper size lead plugs for the small leads which I may have one of, but I would need two for some functions. The lead that I have is brittle, but I could re-use the ends. I have the large screw in lead in good condition. I love the look of this unit and would like to put it to use some day, but that's likely another restoration in its self. I also have an old Simpson VTVM that needs calibration or something as well as a later solid state Simpson that works great. I like to take that one to work to confuse the 'super techs' and even engineers these days. That is what I will probably use for this horizontal output job since analogs supposedly do a better job at giving a good, steady readiing. Of course there is always a dime a dozen digital meter or two around. Mine is decent, but frankly I don't see a big difference between my KAL Equipment job and the ever so popular Flukes we use at work.

I think it is in another thread that this H.O. current is being mentioned and once I read to disconnect a pin that is grounded to the chassis and add a small value capacitor. Then someone else wrote that he didn't get a reading with a capacitor, but he did when he removed it. No doubt, with these threads you can't take every little thing to heart or you might never get a job done. There are too many variables like human and equipment error. But V-K sure a great place to get tips from the best of the best; many of whom were doing this for a job. That sure must have been a great time to be in the electronics profession as all of the home entertainment repair is gone. There are a few bench jobs in industrial equipment repair these days, but I will refrain from getting on that boring topic.

Thanks again folks! I'm feeling the Zenith exitement coming on! Once this coil is in place and with hopefully good results, I will probably be talking about getting the color back. I think I mentioned once before that someone sent me a crystal that is supposed to work as a replacement for the old type that supposedly often go bad. The new part looks almost like a blue disc capacitor. Hopefully this repair will be easy since the set had great color to be at least 20 years dormant, then it just went away completely to black and white, so probably not too difficult. I think its a capacitor frankly, but that's just because they are usually the problem with a long dormant set.

[kramden66]

I had to remove the capacitor that is supposed to be added when doing the ma test on the cathode because the meter I was using wouldn't pass the current to ground with the capacitor there, once removed it went from the cathode to the meter to ground completing the circuit.

[old_coot88]

Tj,
If the HO cathode current was within spec before the eff.coil went springy, very probably it'll be within spec with the new coil once you dip it using the 'magic light bulb' method. Does the HO tube look beat up with heavy black deposits inside the glass or other obvious 'burnt' looks? If not, it was probably running in the safe range.
RS still sells #44 bulbs (cat.# 272-1108).

Kramden66 mentioned using a cap with the meter causing an open-circuit condition (in the cathode leg). He mighta had the cap in series instead of in parallel with the meter.
I never used a capacitor with the meter or saw any need to, since the meter presents a very low (effectively nil) impedance. Like a near-dead short.

Back in the day, there was an adapter (Pomona?) you'd plug into the HO tube socket, then plug the tube into the adapter; it breaks the cathode leg, and two leads coming out of the adapter connect to your milliameter. Doubt if those adapters are still available today, though.

(EDIT) Just a thought.. i never done it, but it might be possible to use a
digital meter for cathode current by shunting it with a very large capacitor to smooth out the raggedy waveform. Several thousand mfd. might keep the meter from going nuts.

[Tubejunke]

Hey kramden66, we have a good and valuable friend in old coot88! It's easy enough to tell that he did this for a living! I do it for a living as well, but I'm sure everyone has read enough of my soapboxing of the "dumbing down" of electronics. It's more or less a plug and play, or throw away world ever since the microprocessor was integrated into electronics. We don't really have a big need to know what used to be almost a given and really is just the fundamentals of electronics. Our knowledge base and training give us the capability and credentials to gain employment in the field; and yes I guess I take a lot of the knowledge for granted and I tend to forget that the average individual without some training doesn't know the difference between alternating and direct current.

Even we tend to forget aspects of the two types of current and their effect on capacitors as was proven by old coot88's reminder of a capacitor's behavior as an open circuit if placed in series with an ammeter and a DC supply. I hadn't really thought of it (or remembered), but it makes sense. With DC a capacitor is charged to its full capacity and then behaves like an open circuit with AC because of polarity reversal this charge and discharge cycle continue and the current continues to flow in the external circuit. There is no frequency with direct current, so there can't be capacitive reactance. X sub C = 2 x pie x frequency x capacitance if I remember right.

My HO tube doesn't look burned up, but when I first brought the set home there was no HV and the tube was red plated. It's been so long I don't remember all the specifics, but I think one of the tubes was damaged, maybe cracked. Seems like it was one of the tubes inside the HV cage. I replaced that and I think one other tube extenal of the cage that's related to sweep and gained HV and no red plate. It wasn't long before I discovered this coil and haven't had much power up time at all on the set. I didn't want to risk any flyback damage since I have read so much about it with these color sets which I typically never mess with, so my knowledge on a lot of the particulars of these sets is very limited.

[Tubejunke]

OK, I installed the Efficiency coil finally. No real change, but there wasn't really a problem other than knowing that there was a broken part in the set that could cause damage to the set that could be avoided. I didn't work the set long as I still haven't wired in an amp meter and checked the cathode current.

I did notice a bit of hissing in the H.V. cage that led me to play with the slug a little. I could adjust a little and it would go away along with the on screen jitters that come with corona discharge. The discharge is very light; not a loud hiss or snapping like I have heard. I turned the H.V. adjustment down a little and it didn't make any difference. I need to get a meter on this puppy.

I have heard of moisture collecting in long dormant sets and noise from the cage being an issue until the set works long enough to dry out well.