Checking Vertical Output Transformers??

[Tubejunke]

I am still battling the 1958 Zenith Space Command (18C24Q) that I have posted many times on being stumped on a recap that produced no improvement in the set with little vertical sweep and hum for sound.

My latest efforts have been disconnecting the transformer leads and yoke leads in order to take some resistance readings.

On the transformer I get 317 and 326 ohms across the two sections and 9.6 ohms between the two. Infinity to chassis. Does anything sound off?

With the yoke its hard to know what to do. Inside the back cover are several resistors and a capacitor. Best I can tell two 560 ohm resistors work in the vertical winding portion. Neither of those 10% resistors was higher than 609 ohms. I disconnected both resistors to attempt getting winding measurments. I came up with 22 ohms between three different points. From a similar set schematic that I have 22 ohms is a good reading but shouldnt I get that reading at four sepearate test points if reading the resistance of two seperate windings? Does that make sense?

Anyhow that's where I am at with this great looking DISASTER..

This set is in such great shape it is unbelievable. It looks as if it was only ever used a couple of years with nearly all Zenith stock tubes and a super healthy crt. Someday I feel like whatever crazy thing is keeping this set from working will surface and the set will be a good one for normal use with the large 24" crt and remote control. Not quite run of the mill.

If anybody has a remote for one of these I need it.

[cbenham]

[QUOTE=Tubejunke;1359383]
"On the transformer I get 317 and 326 ohms across the two sections and 9.6 ohms between the two. Infinity to chassis. Does anything sound off?"

Sounds OK. Your yoke readings sound OK too, but make sure the vertical windings aren't shorted to the horizontal windings or to ground if there is a groundwire to the yoke. Do you have the right B+ voltages on the vertical circuit for the Osc. and the output?

Best Luck,
Cliff

[Tubejunke]

Actually I don't know. To be honest I do most of my work with an ohm meter trying to weed out faulty components. Not that I can't check voltages but with some sets I refrain due to having to separate the chassis from the crt and in this case the tuner. I am afraid I will screw something up operating a chassis with a bunch of stuff unplugged. Would it hurt to fire this chassis up by its self long enough to check some voltages?

Also I dont like that 2nd anode HV lead flopping around! I know I can disable the HV by pulling a tube. I heard that you can mess something up doing that. I forget if it was somehow messing up the flyback by some kind of oveload caused by the horizontal oscillator or what. I may not be making sense.

Yes a lot of my repair work is fairly crude. At least in method. The actual job I do is fine. I wish I could use scopes and all that good stuff. I probably would have had this set licked in a matter of hours, instead of years.....

Any help or advise with this old news is greatly apreciated!!!

[Tube TV]

If you can, get a B&K television analyst in can create it's own vertical and horizontal currents , I bought one on e bay and it was the best money I've spent . Could there be a black beauty capacitor that was overlooked as a resistor ? Your ohms reading sound ok . can you hear any vert oscillator sound? also check for parts touching in the sound circuit .
Does this set have selenium rectifiers ?

[fsjonsey]

$2 worth of rectifier diodes did wonders for my bugeye.

[bgadow]

Tubejunke, if you do want one of those analysts let me know...I have a couple. They both need some caps. I could send one down with the crt...

[Tubejunke]

Hi Bryan, I just sent you another PM. However with everything going on I forgot to mention the "analyst". No I don't have one. It sounds pretty cool. If I did have it I would not know how to use it. That is no matter, I'm sure you or someone here would be able to enlighten me on its use. I don't know what they are worth so I don't know if I should tell you to send one down. By the time I will be back on here you will have already met Charles for the crt pickup. What to do?

By the way I just picked up a Mercury Model 204 tube tester. It is one from a local electronics shop with the lit sign above the scroll. I have actually used it over half of my life. It has a small problem that I hope I can fix because this setup will test almost all tube #'s. My older Sylvania only has specs up to the late 50's.

[Tubejunke]

Originally Posted by Tube TV

Your ohms reading sound ok . can you hear any vert oscillator sound? also check for parts touching in the sound circuit .
Does this set have selenium rectifiers ?

Sorry for the delayed response and thank you for showing interest. To answer your questions: Yes I can hear the "oscillator sound" but to me it sounds very slow. I have looked and looked for something touching and causing this whole thing. So far nothing. The set has no selenium rectifiers thank God. It is a transformer set that employs a 5AU4 tube. As far as the power supply goes everything seems fine. The 2nd anode high voltage and the sound (HUM) will work fine and produce the line on the screen (almost no vertical sweep) without fail. This to me indicates that the power supply is up to par and producing DC as needed. When I say "almost" no vertical sweep what I mean is I can only squeeze maybe a 2" high raster by tweaking the size and linearity pots.

I keep wondering about the remote control chassis and what effect it could have on the main chassis. They are interlocked and neither chassis will power up without the other plugged in. I cant see any way that the remote circuitry could effect vertical sweep though. Now I can see it effecting the sound possibly as it does control volume.

I hope to soon figure something out with this. It has been haunting me for a few years now. If someone here was big into the old Zenith remote sets particularly I would be in luck. The sets are actually known I believe for being good performers.

Oh, I forgot to add that the other night I pulled a 6EA8 from the tuner for a test and there is some indication of a short. Its weird, the short light shows up very dim, if at all until I put my hand on the tube and then the light glows brighter. Thats weird. The tube is the Mixer/Oscillator. I have not yet checked the other tube, the R.F.Amplifier.

A short ANYWHERE has been what I have expected to find as far as getting rid of HUMMMMM and possibly restoring a signal which so far I am not getting.

LOTS of issues from a set that LOOKS brand new!!!

[Tube TV]

I've got the manual for the 1076 model , they are pretty much the same of the 1077 ,just the contols are in different places . I could get you copy in the next couple of months when I get the scanner . they are really handy . I use mine quite a bit .

Hey fsjonsey did you see the bug eye on ebay? it's in texas ,it is the same as yours , last time I checked there were no bids . nice parts set , lots to ship though .

[Tubejunke]

What is a 1076/1077? Is that the "bug eye" someone de-selenium'd? Yes, I have heard that there is a certain # diode that you can buy from Radio Shack (if the kid knows what you are talking about) and wire them in the place of the nasty selenium rectifiers.

I tried it once based on some info given to me and all I got was an instant loud POP. End of diode! I dont know if the info (value) was wrong or if I reversed the polarity. You can also take an octal tube base and turn a rectifier tube like a 5U4 into solid state with diodes of a given value and a resistor to duplcate the tubes internal heater resistance.

I need to look up the 5U4 conversion and get the right formula. If I get it I'll post it. Those things arent getting any cheaper. They last forever and a day but bringing home a set full of long dormant electrolytics can cause you to cut through several before you (I) get sence enough to forget any thoughts of plug and play and change out all of the power supply filters.

[Findm-Keepm]

The 1076/1077 are B&K Precision TV Analysts - you can use them to substitute signals (Vert and Horiz drive, Video, IF/RF, even color signals). Here's a link that explains them better than I ever could.

http://www.wkinsler.com/radios/analyst.html

Not me, and no, I don't know them either.

Cheers,

[Tube TV]

I had the same problem , I bypassed the seleniums and put in diodes and had the same problem . I had salvaged them out of a stereo . It turned out that one was connected wrong , seleniums are hard to find info on and I fried one diode . I didnt have the schematics for the set .


The 6EA8 should be fine . my tube checker is a sencore mighty mite and it does this sometimes and it will also have the wrong grid leakage readings when the humidity is high .

the vertical hum , is it strong or weak , check the controls for vert size , vert line ect. and see it they are changing in ohms , you may have to remove the wires on them to do this . I would also look through the resistors especially anything from the power to the vert circuit . something in there might weak in there. If you have the schematic check the voltages in the set and see if there is somthing running low .
when you done the recap , did you do the filters?

If I was going to put my finger on the problem I would say it was in the power supply .

Is the remote system tube or transistor ?
Is is switched on with a relay ? of does it only change channels
I doubt that it is in there .

will the TV pick up stations at all ?

[Tubejunke]

The hum is strong but volume control adjustable. Yes, the first thing I change in any set is the power supply filtersso that is done. No, the tv doesent seem to pick up any signal at all.

Now, you can alter the sound of the hum with the "buzz" controlon the back of the chassis. As for the remote chassis it is a tube setup that has on/off, channel select, and volume control. It IS directly linked into the power supply. The set wont come on without plugging the remote chassis in. That is what made me wonder if a short in the remote circuitry could come in through the power supply somehow. This is a 1958/9 model by the way.

The reason I don't think its the power supply is the fact that what does work works well, and that is the horiz, HV, sound sections. All of this is stable. Would that not indicate that enough dc is being produced. Nothing is running hot also. Power transformer is nice and cool. All caps are cool.

The whole thing has been strange. Again the set is NO different in what it does do now than before I changed the first part. Its really heart breaking to replace all those caps and resistors and achieve NOTHING at all. Know what I mean? I think something went wrong with this set early in its existance and it was not figured out then. So the owners stored it for years and finally it ends up in a thrift store. Back then you didnt toss everything that broke and a 24" Zenith with a beautiful cabinet was somewhat of an investment. Probably $300-$400....

Again thanks for the interest. I have mentioned this thing a few times over the past few years and never get much feedback. I have found that surprising since Zenith is a common name and they used very similar chassis for a fair amount of years. Also being an early remote set I thought there may be some interest in these......guess not..

[Tube TV]

I know what you mean , I have a General electric like this exept it's the horizontal . and it is enough to drive you nuts it has had new caps ect. still not working .

It might be in the remote circuit .

im looking at a schematic is for a Canadian Zenith (19B20 , Q) Just using it as a reference . And the power supply is fairly simple . if it's like this one , it should be developing + 265v at the 80 MFD filter this is the B+ voltage
this voltage goes to the plate on the damper , after going through a spook coil assembly . This would cause me to think that the power supply is good as well , however this might be enough to run the horizontal but not the vert oscillator at full capacity check your voltage on your chassis .
does your set have ,
6CG7 VERT OSC .
6CK4 VERT OUT . ? that's what is on this schematic

is the HUM , a 60 cycle hum or does it's frequencey change when moving the vertical controls ? Im begining to think it might be a bias voltage that is low or a weak power resistor somwhere in there .

Do you have schematics for your Zenith ?

eventually it will run .

[Tubejunke]

My set has the 6CG7/6CK4 combination. I have a schematic but it not a Sams and it is not for my exact model. However if I remember right the tubes are all the same which should make all or most of the specs and component values the same. It leaves out info on the remote chassis all together.

I mentioned somewhere before that I was skeptical about checking voltages on a chassis sitting on a bench with no crt. The only way I would feel safe would be to disable the HV to the CRT second anode. There is a proper way to do this and I think it is to remove the horizontal oscillator tube as opposed to just disconnecting the cap from the top of the tube. This is to avoid harming the flyback somehow I think. Is this correct? Also will a chassis operating with various things disconnected cause other harm to the set or give incorrect voltage measurements?

About the hum, the frequency is not effected at all by any vertical controls. Only the volume control or the "buzz" control effects the sound of the hum, not the frequency though.

About the remote chassis somehow causing trouble, I still wonder. There is a switch to cut the power to the remote chassis and use the set manually. You would think that IF the remote chassis was causing a problem opening that switch should isolate it and thus eliminate the problem. Still it is funny how they set up the thing so the power supply is disabled unless the remote chassis is plugged in. I guess if the set were NOT a remote set there would be some kind of jumper in that socket or no socket at all.

Thats it for today. Thanks a mill for the positive outlook on this set...