Since I couldn't GIVE it away, I guess I will do what I should have done in the first place and find out where the mystery short is in my 1959 24" Zenith Space Command. I have posted about this set plenty of times, so for those who have already heard my woes, please overlook while I bring the story up to date.

When I brought this set in, it had the usual coating of dust, but under that dust was a super clean chassis with all stock Zenith tubes and the CRT tests like new. Just that made me feel like the job would be a breeze if not a "plug and play." Well, no such luck! After a slow warm-up I powered it up and had a volume adjustable hum with no vertical sweep. So, I bought all of the capacitors that I would need and installed them. I replaced everything but the ceramic discs. I was surprised that after the job was done I had exactly the same symptoms!:thumbsdn:

That was a couple of years ago. After carefully looking for any solder bridges and bad resistors I wrote the set off as one that "stumped" me. THAT was before I attended college in a electronics degree program. If the program taught me nothing else it taught me that there is no such thing as "stumped"! When a problem exists, I should be able to figure it out! One thing that holds me back in troubleshooting THIS chassis is the fact that there is no way to check voltages with everything hooked up unless Zenith had sense enough to design a voltage check chart so key voltages could be checked from the top via the connection strips. If the DID do this, I would like to find a copy of the information. Also, here at home I do not have some of the professional equipment that one may use in troubleshooting, so I am stuck with a DVOM and a tube tester.

I must ad the fact that in my last component check I did that I found a weird looking coil that looked more like an insect larvae than a component; it was open. It was located somewhere in, if memory serves me correctly, the video circuitry. The only marking was a GREEN dot on the blackish gelatin looking exterior of the thing which protrudes through a hole in the chassis and is more or less hidden by one of the cans where a larger adjustable coil is mounted with a small ceramic disc and a solid state diode connected. Anyway, I doubt seriously that this is the heart of the problem, but if I ever get vertical sweep and proper sound this coil WILL need to be replaced and I am not sure how to identify it.

What led me to start this thread though was an afterthought that I had concerning what symptoms may arise as components become faulty within the remote control chassis. I mean, after all, it is directly connected to the main chassis, so I would think that it could have at least some effect. However, you can turn the remote unit off and you would think that turning it off would eliminate this possibility. I would like to know as not too many people talk about remote control issues. I am not concerned at this time in getting the remote working as the control is missing. I just want to make sure that it is not the issue that keeps me from repairing this set.

If anyone had any tips one these Zeniths I would really appreciate the lead. My next step is to remove the vertical output transformer and check for shorted windings as best I can with an ohm meter and no specs. At least I can tell if either lead is shorted to ground or open. I would think that a dead short to ground would have something heating up and/or smoking out which is not the case. I think that a Megger is the best thing for really checking windings. I also need to check tube sockets for bad connections. Other than that, I hope someone here familiar with what is supposed to be one of the best performing chassis ever made will have some ideas! :thmbsp:

Thanks in advance!

One thing that holds me back in troubleshooting THIS chassis is the fact that there is no way to check voltages with everything hooked up unless Zenith had sense enough to design a voltage check chart so key voltages could be checked from the top via the connection strips.

These socket extenders can be quite handy.

http://cgi.ebay.com/Two-Socket-Test-Vector-T80C-Peco-TVS-9-Nice-Condition-/150521728598?pt=Vintage_Electronics_R2&hash=item230bcb4e56
not affiliated,
jr

I have not seen this model personally but it's chassis mounts vertically, correct? You should be able to remove the chassis being mounted to the front bezel and CRT as an assembly so you have exposure to the backside. If you have the Howard Sams, it should have some specified test points on some of those terminal strips.

As for the remote chassis, there may not be any schematic info for it. I have an older model Zenith than yours (Z3000 chassis 17Z23Q/ Howard Sams 343-18) with remote and no data is supplied or listed as a suppliment either. I'm sure it may exist in some Zenith book somewhere....

Those tube extenders are handy to have though!

Wow, thanks for reminding me of those folks! I remember seeing them in the Antique Electronics catalog, but just never really thought about using them. I could check a lot of voltages with the chassis in place that way! Zenith may have mounted some of their chassis vertically somewhere back toward the mid-fifties, but I know that they used variations of my Zenith's 18C24Q chassis till up around the mid-sixties and it is mounted horizontally. I have seen schematics of the variations of this chassis and they just changed a few of the tubes that they were using and eventually eliminated the vacuum tube low voltage rectifier in favor of the germanium diode.

There is no way to remove the chassis and CRT together at all. A shop would have had one of those small universal test CRTs and other extension cables to use in situations like this. It would not be too hard to just make a test jig just for this job which would entail setting the chassis up vertically and holding the CRT, chassis, and yoke firmly in place. It might be a good idea to find a plug and socket that will accommodate the leads to the yoke and make an extension there. If nothing else, it will be good to have a way to disconnect the yoke from on top. Many manufacturers did things like that in the early days because almost all repairmen were learning the television end of electronics at the same time, the manufacturers wanted armys of competent techs that could keep their product lines going. A television purchase was once a fairly big deal as far as investment, and it certainly was not tossed in a dumpster when it went on the "fritz." I think that American product manufacture and the product support of the old days was beautiful, and it's LACK is a big part of what is so very WRONG with the American business world and the business ethics of more recent decades and certainly today.

As far as remote chassis' go, normally if a set was manufactured with remote control capapbility, then it was reflected in a Sams or Riders folder somewhere. I have a schematic of mine. I am just curious as to the troubles they can cause as they are certainly interfaced with the main chassis. Perhaps someone here can point Marty in the right direction for a schematic on a PDF file for his 17Z23Q chassis.

Anyway, the series of chassis that I spoke of (18C24Q and similar) was supposedly pretty notorious for high use with little or no troubles. I know that I need to post a picture of the chassis to give this thread some zip.

The Sams should be a 343-18
I think the first priority is to get one scanned so we can all look at it and follow along.

Next would be some pictures of the chassis front and back along with a detailed description of what the symptoms are.

Most older consoles the chassis and CRT were all one unit that slid out of the cabinet, you are saying this isn't the case here?

It may still be possible to turn the chassis enough with the cable attached to work on it.

Um Eric, my first (very long) post was pretty well detailed. I wouldn't know much else to say. Sure, pictures always help I know, but I have dial-up Internet and pics take a LONG time to upload. The set is already pictured in at least one other thread of mine. I will try to find out which.

Frankly, I am surprised that so far nobody is familiar with one of Zenith's most popular chassis designs that again was used in variations for several years if not a decade. I have some old sets that the chassis comes out with the CRT and others that don't. The older ones usually do come out as a unit because most CRTs were 19" or less. Then the larger 21" took over and sort of became a standard during the mid and later 1950s. My set has a 24" CRT which was rather large for the time, so they bolted all of that weight to the cabinet thinking that repair would be easier on the repairman's back. Again, a shop would have the necessary extension cables and test CRTs for this type of set. I just don't....

It's been a while since your original post, I couldn't find it, if you can find it and link it it would be helpful.

I didn't know the tube was attached to the cabinet, that makes it more difficult.

A Sams will still be helpful, I don't think I have that one but perhaps someone else does and could scan it?

Can you stand the chassis behind the cabinet and scoot it close enough to hook things up?

http://antiqueradio.org/art/RCACTC-11ChassisOut.jpg

Or, perhaps you can slide it partway out and still make connections. In this case, I only had to extend the speaker leads.

http://antiqueradio.org/art/21t2276.jpg

In another case, I temporarily soldered wires to test points and ran them out to where I could access them when the chassis was fully installed.

Just some ideas . . .

Phil Nelson

Can you stand the chassis behind the cabinet and scoot it close enough to hook things up?

Or, perhaps you can slide it partway out and still make connections. In this case, I only had to extend the speaker leads.Phil Nelson

Hi Phil, thanks for the good ideas! I have tried one or two in the past, but it's been a while. Two problems I face with this chassis are: one, the yoke is mounted to the top of the HV cage by a steel bracket and is on very short leads; and two, the second anode connection to the CRT is so short that there is little or no room for manipulation. I am almost certain that sets like this are the reason why they made that universal test crt that is very small. It would be perfect in this case! :thmbsp:

[QUOTE=Eric H;2987875]It's been a while since your original post, I couldn't find it, if you can find it and link it it would be helpful.QUOTE]

Hey Phil, I looked too and found no pictures. Maybe I posted pics on AudioKarma before the split. Anyway, you mentioned cut and dry symptoms so I decided to re-list them to avoid confusion:

1. No vertical sweep. Turning the LIN and Height controls way out of range will get maybe one inch of sweep.

2. Volume adjustable hum for sound with no evidence of signal presence.

3. Open coil that I am not sure how to identify. Black rubbery coating with a green dot on the side. Around 3/4" in length by maybe 3/16" diameter. I am pretty sure it is in the video section and it is mostly hidden inside one of the coil cans. I have a schematic coming and I can be more specific concerning location. It seems like I saw a schematic once before and no part# was given for the coil; only a resistance value.

This is the way the set was when I got it AND after replacing all of the capacitors except ceramic discs. I wish I had an LCR (?) meter! I have DVOM's with capacity function, but I am told that they are not accurate.

Right now, I am primarily focused on getting the sweep and finding out what the constant hum is about. Since they are both such persistent symptoms I figure that somehow they might be the same problem.

Two problems I face with this chassis are:
Yah, I just got a DuMont RA-113 with similar issues. The yoke hangs from the cabinet ceiling and all of the leads are short. Impossible to play on the workbench unless I build a stout frame (almost a box) to hold both the yoke and CRT, which ain't gonna happen. I found a guy with a test CRT. He wants $75 + shipping. My plan is to finish recapping and then see how it works in the cabinet. The top of the chassis is quite accessible when it's installed, so maybe those hijinks won't be necessary.

Phil

I found a guy with a test CRT. He wants $75 + shipping. Phil

If you find another test CRT please PM me! I think that this is the REAL way to win the battle. Those DuMont's are bulletproof and EVERYTHING is heavy! I would hate to be trying to buy, or have built, a power transformer for something like an RA109-A!