Checking Vertical Output Transformers??
 

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.

[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

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!!!

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 ?

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

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...

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.

Sorry for the delayed response and thank you for showing interest.:thmbsp: 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. :scratch2:

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!!!:no:

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 .:thmbsp:

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 .

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.

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,

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 ?

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..

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 .:thmbsp:

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...

Zenith space command
 

I have a schematic for the space command remote chassis .
Does yours have 3 6AU6s and 1 6AL5 1 6CM7 ? If so Ive got the info for it.
these were in canadian models in 1958-59
I would say it would be safe if you pulled the horizontal output the flyback will be protected and there would be no high voltage .
the hum , what cycle is it ? is it 60 cycle or is it different ?
that's good that your set has the same vertical circuit as my schematics
it's probably the same circuit . you might be right about the remote chassis
causing problems and I have the info for the chassis plug and the socket wiring into the tv chassis .
Does you socket have 8 pins all around then the 9th is more towards the center ?

I can get you copies of this if it's the one that fits your set .


Any susgestions or comments please , if disconnecting the horizontal output tube would be allright ?

My remote chassis uses 3-6AU6, 2-6CM7, 2-6AL5, and 1-5Y3GT. The power connection is a 3 wire rectangular plug that inserts beside the main power transformer, also there is a 5 wire round socket for the wires from the tuner motor.

I think it would be safe to call the hum a 60 cycle. It is similar to what you hear when you have bad caps in a power supply. Actually I didnt know that there were different kinds of hum. I started in working on old radios and I have heard many a radio with a similar hum.

What method do you use for measuring voltages when a chassis must be separated from other components? Maybe I know the answer to my question. You could use jumper wires or extentions and a test crt in order to have the chassis doing what it is supposed to do on the bench. In my situation again the crt, the tuner, and remote chassis are out of circuit when the main chassis is removed.

Tubejunke , I got that schematic too, the rectangular pin has , black , gray , blue wires on it ,it should be blue they are coded as BL im assuming they are blue . Two of these go to a power trans then the 5Y3 , that operates the remote system . there appears to be a 5 pin plug for the motor however I can only find 4 wires , the 5th center terminal has no connection . there is also 1 selenium rectifier in the power supply . does yours have that ?
Would you like a copy of these schematics ?
When I have measured voltages in the past I have had the tube out , some sets you can flip the chassis and connect it to the picture tube . but this might be easier said than done , alot of the TV's I have are not bigger than
17 "
How would it be to remove the controls and the CRT ? your best bet is the extentions like you said earlier .

Like I say , I have the schematics , If you want them send me a PM with your address and I will get you a photocopy of them .
I would scan them but I still havent got a scanner yet .

murray

TJ, did you change all the can type capacitors or just the one for the power supply? (usually C1)

One of the cans is connected to the vertical and will kill it if it's bad.

I just got done with a Zenith Flash Matic and it was a bit of a pain, I had to remove the tuner and remote chassis and hook them up on the bench.
It wasn't as bad as it sounds, my tuner just had two screws holding it in the back and a slotted bracket up front, popped it right out and hooked it up.

A test CRT like this one is a big big help:
http://cgi.ebay.com/Vintage-NOS-GE-G...QQcmdZViewItem

Same thing but in a box: http://cgi.ebay.com/Tele-Check-Model...QQcmdZViewItem

It gives you a place to hook the second anode up and you can see what the set is doing while you work.

Hi Eric, yes I changed all of the multi-section cans on mu chassis. As for the test crt I have known that they were once available when shops still repaired what we now consider "vintage". Thanks for the link. For those of us who do not have one and want to check some voltages a couple of us are wondering what the right way would be to aproach doing this on a chassis that has been separated from the crt and tuner. I know jumper wires are one way. However it would be a pain to extend the yoke wires to a remote location.

Obviously you wouldnt want 2nd anode voltage flopping arond loke a Cobra snake. I have heard to remove the horizontal oscillator tube to disable HV and avoid some kind of damage to the flyback. Does everything have to be hooked up to check power supply, sound, and vertical circuit voltages?

To my friend Murray I am sending you a PM and for the thread no my set does not have any selenium rectifiers. Transformer and tube all the way here..

Tubejunke, I got your PM this evening , I will mail the remote chassis schematics the next time im in town .
probably in a few days .

Murray.

Thanks a mill Murray!!!

The original diode sounds good . Im not sure if you already know a easy way to test diodes , but this is how I do it . a analog meter is easier for this .
Touch one lead onto the anode and the other one on the cathode .
depeding on the polarity it will read about 2 k or if it is in the other position it will read anywhere from 40 K to 100k .
for example , you touch the test leads on the diode , it read 2K
you reverse the leads red lead where the black was , if it then reads 40K the diode is allright .
If it was defective it would read for example 2k and when it is reversed 2K .
The other thing that happens is the when it is open it will read 100k or more either polarity .
then there is the shorted diode where either polarity reads 0 ohms or 100 ohms .
the main thing you want to look for is this ohms variance between the polarities , this indicates that the diode is allowing current to pass in only one direction .

Im glad to hear that your Zenith has the same schematics . I got the scanner last week I could send you the alignment info for it once you get it running .
I looked the # of the diode that you bought in my ECG cross referance , I have no listing on it , I am surpised that it was not in there .
A rectifier diode out of a old transistor tabe radio or other small Item should have one that will work .
It seems to be for the bias for some of the tubes " 19 volts 12k ,22k 26volts"
note on the resistor next to C17 , just ahead of the diode . it dosnt seem to handle any great current
what was the schematic # on bipolar capacitor you changed ?
Then I will know where it is in the circuit .

Tubejunke , Is this like your chassis layout?

Tonight I used a better meter and got some odd results. The old diode measures 10 meg ohm one direction and about 5 or 6 meg the other direction. The real weird thing is the old diode seems to have a capacitor like effect on the meter, only backwards. The scale actually counts down if you hold the leads on it for a minute.

The new diode measures a rock solid 250K one way and infinity the other. I smell trouble with those high and erratic readings with that old diode. I have always heard that a rectifier diode should pass virtually no current one direction. My readings are far from that.

As far as my new diode being correct the package mentions that the diode replaces ECG116, GE-504A, And SK3313.

The non polarized cap I mentioned looks like it says C25. Getting the c25 was probably dumb as far as WHERE it is on the schematic. I mean it is across two relays and eventually goes into the motor socket. Obviously something to do with the channel select signal process. I bought it mainly because I wanted to replace all of the electrolytics and that diode on hope that something might come of it. There are only 3 or so other electrolytics that I already have in stock.

fun with the Zenith space command !
 

That reading sounds funny to me also , the replacement diode is good for 1 amp of forward current max . It will work fine in there , the old one might be feeding AC into the bias section causing the 60 cycle hum and also weakening the vertical oscillator causing the output to be less . I would say change it , you have nothing to loose on it .
let me know how it goes .:thmbsp:

Tubejunke , Does that look like your tube list and chassis layout in my previous post ?

I'll try it out this weekend. Your last statement is exactly what I was thinking. I just have a rudimentary knowledge of electronics. So I wasnt sure if I would have been making a stupid statement. I understand a whole lot but I have a long ways to go. Thats why this site is do great. I can ask for advice and sometimes give advice.

What we are doing with vintage equipment is not taught in school anymore. Most young techs with a degree and a fat wallet would look at you like you were crazy if you slapped an old 50's tv on his bench and said fix it...Its great we can keep this knowlege alive.

And yes, the last tube layout is what I have...

Thanks
Tube

fun with the 58 space command
 

I have the same problem here the last tech retired last year , and he was not interested in tubes that much , I always get told , " why do you want to fix that , its B&W and it old ?" All I tell them is , " Thats the whole point or my collection " .
Audiokarma is a great place , I really enjoy discussing old tv's and doing what I can to help out a fellow collector .
I ran into a previous thread from 2004 , since then have you changed the electolytics ? and the 5U4 ?
If you want to leave the cans , there is a great unit for testing them .
A Heathkit capacitor checker ,the C-3 is a great unit and will test for leakage using a voltage source it suppies to the cap at the proper working voltage .then it determines if the cap is leaking or not ,plus it has a resistor checker in it also , it uses a magic eye . They sell for 35 buck usually .
It would pick out problem parts in a hurry .
I have the sencore LC2 leakage checker and I dont know how I lived without it .
It's the best $ 28.00 I ever spent .
I will go throught the schematics that I have and see what I can find that is perhaps powering the vertical , and also the sound circuit .
Good luck with the diode . :thmbsp:

Yes I changed all of the elecrolytics. When I brought it home and heard the hum and saw the lack of vertical sweep I knew (thought) it was time for a simple cap renew. Now here I am a few years later with the same symptoms.

I changed the bad diode tonight. No change. I really had some faith built up in this and STILL nothing. I just dont get it. Actually the oscillator sounds like it is running at a more normal speed and I have maybe 3" of height. Still no signal at all. I've checked and or changed all of the tubes. This one is for a pro I guess. If the set were of the type that the chassis and crt pulled out together I could at least do some voltage checks. This set is in pieces every time I yank the chassis.

Too bad there are not many pro's left. If so I would just take it to a shop and say FIX IT. Someone who is set up to do this and has the knowledge would likely figure this out in no time at all.

I hate this failure because the set is in like new condition and its a waste to have it sit around useless or worse a shame to scrap.

I would love to have one of those capacitor test units. I have a couple of DVOM's that have a capacity setting but there is no load applied, which is the key to a proper test.

Tubejunke , try this , just to see if the vertical oscillator is running , once you have the set on , turn the vertical hold control and listen to the vertical output transformer you will hear that typical buzzing sound ( pull the wire off the speaker if nessisary ) turn the vert hold , the buzzing sound should change in speed , slower or faster it is normaly locked in by the sync at 60 cycle produced by the oscillator , The vertical oscillator creates a sawtooth pattern , but a sine wave will drive the vertical output . there could be a signal comming off the power supply that is interfering with the vertical osc but still creating some raster because the line current is 120 V 60 cycle .
If the sound from the vertical oscilator varies than this would indicate that it is oscillating , if not that is would mean that there is a loss of voltage in the power supply or a loss of a bias volage in the oscillator perhaps .:thmbsp:

I have been taking note of the presence of the sound of the transformer. Earlier on in all this I remember the hearing the sound but it sounded oddly slow. Now the sound is much faster. It sounds like any of my other working sets. I just can't get the sweep, or not much anyway.

One thing that I noticed is that what height I can get seems to go from the center of the crt up, if that makes sense. I can tweak the vert lin. and vert. height controls and I notice that only one of them effects the sweep. What it seems to do is raise the height from a collapsed line up, never down. I always thought that the lin. and height controled separately the upper and lower portions of the raster.

I guess my next step will be pulling the chassis again and doing a piece by piece check on resistors. I have done this once before but perhaps I missed something. Of course I have tried different tubes in the vert, sound, and tuner sections.

Thanks for sticking with me on this. I guess the subject is getting boring by now. Maybe I'll have good news one day.

Do you think you could find a Thordarson or Merit yoke cross reference for me? I have a supply of NOS Flybacks and Yokes. If I had this one in stock I could pop it in just to see if the yoke is the sweep problem and the lack of signal and hum is a whole different problem.

Tubejunke , Im not bored with this thead yet , im actually having fun:banana:
have you checked the filter \ choke , it's on the start of the B+ line just after the 5AU4 .
while you got the chassis out check the B+ voltage and see how much it is putting out according to my schematic it should be producing +265 volts .
I was looking at the schematic that I have and it looks like it would be allright to pull the horizontal output tube to stopp the high voltage supply .
That way we can eliminate the B+ as a source of the problem .
It might be hard to measure this because of all the remote circuits , but it might be worth it to do .
Let me know how thing go with it .:thmbsp: