Westinghouse TV no picture : Strip or fix?

[Old1625]

The "gassy" sound you were hearing was likely high voltage arcing and leakage. It is a "hsssssss" that may sound like gas leaking from a crack in a pipe or cylinder. If the HV leakage is severe enough it will keep any image from forming on the screen at all. As the leakage diminishes then whatever image can show will show on the screen. Perhaps the warming of the set has driven out the moisture that enabled such discharge to occur.

As for the gray raster with no snow you may want to examine the sound output tube--believe it or not. A lot of these old sets used the sound output tube as a series voltage regulator, where all the picture IF stages and the tuner would feed off a 130 volt supply right off the cathode of the sound output tube. If the tube is flashing over then it is possible that it is weak or altogether bad, or that the electrolytic capacitor on the 130 volt line is shorted or severely leaky. Either way the result is that there is low or no 130 B+ supply to the tuner or the picture IF stages. Sometimes with this problem one can turn the volume control way down, and then turn it up rapidly, and the raster will suddenly brighten and produce snow for a brief moment. The output tube can be weak enough to supply insufficient B+, but still have enough life to produce sound.

(Edit) Reading your last posting where you get sound but no picture at all leads me to want to re-examine the video amp stages.

[jpdylon]

The vertical output tube needs to be replaced. the blue glow indicates a gassy tube (air has gotten inside the vacuum.) If you're hearing sound but only seeing gray, there is a problem in the video amplifier section. Could be a tube, but more likely some bad capacitors. If you haven't replaced the paper coupling caps in this set you can't really judge its operation condition or really begin to troubleshoot until you do.

The vertical linearity interacts with the vertical height adjustment to make the picture vertically symmetrical and not too stretched or compressed at the top or bottom.

[JesusJones]

Alright well I have the tubes I need.(Courtesy an AK member, Thank you very much)

So I can switch them out, I am just concerned that I may destroy the new tubes I put in. Roughly how much bad operation can a tube handle. Will they be destroyed within minutes. Or should I not worry.

And yes I was getting arcing. From the top of the HV coil. I mentioned it was chipped there before. Last night I finally saw it jump from that point to the frame.
Here was my simple solution to add insulation. Hot glue gun. Its rubber, rubber insulates and it's fast and easy. Maybe some one else will find that trick handy.

Rudy

[jpdylon]

THe hot glue gun is ok, but most will use a silicone RTV designed to work around HV. They usually stops the problem in the short term. Make sure the HV cage around the coil is clean and without dust. Dusty cages will cause corona discharge and arcing.

If the tube is glowing blue - its usually the fault of the tube and not the support components. However, arching inside tubes can be either the tube or the supporting components. You're gotten this far, I would really consider replacing the capacitors in the set. They are not expensive and it will mean that in the long run the set can be operated in a reliable state.

[JesusJones]

The dust I have cleaned off with a toothbrush The cage I washed. It's spotless.

I've put new tubes in where needed. And am going to test it out. If I see blue or arcing the caps will be changed. I changed all the electrolytic already. But some are axial not radial.
The coupling caps looked like inductors to me. It wasn't untill after I made my cap order I realized they were coupling capacitors. They are radial type. Not electrolytic. They look good but....yea your right They probably need to go.
There's also a black beauty near v15. I suspect he MUST go. But I can't figure out its value. It only has three lines on it. Starting from the end with a blob of solder It's blue orange brown. And very faintly they're may be two more brown lines on each side of the orange band. Any one know what value this may be. Cause I don't think its coincidence that the tube that glows blue has the only bumble bee cap in the whole circuit right next to it.

And here in Winnipeg caps aren't cheap!! I went to a place some one told me it was cheap to buy from. It was $17 for one electrolytic rated at 450 volts and low mfd.
Another place offered me electrolytics for around $8 a cap. I had to order mine online in order to get my money's worth.

[JesusJones]

Definatley works better. There is no blue. There is no arcing in the audio output tube. And you can actually hear stuff better. But still there's no picture.
I guess it's time to get some more caps. Bummer

And cathode of the audio output is at 144 volts according to my meter. 12 volts too high. Any suggestions on how to get this down? Or no worries?

[nasadowsk]

12 volts isn't gonna make a huge difference, or at least shouldn't - measure the cathode/grid voltage and see what it is. But if you get decent sound, I'd not worry.

Trace out the BB's wires and see where they go - you can use that to figure out where in the circuit it is.

As long as you're getting a raster on the CRT, you've got the basics and it's just capacitor replacement and checking things out. Don't worry that you're not getting a picture - it's in there you jusdt need to find where it's getting lost.

Seriously, at this point, you're gonna need an oscilloscope (and an isolation tranny to keep from blowing up a scope). With a 'scope, tracing out these issues is really easy and fast - you SEE what stage the video gets lost at, or what the vertical signal looks like, etc. A used one shouldn't be too much, and it pays for itself fast.

You've got a TV set that's got the basics working, it just needs some cap replacement and some targeted diagnostics. But unless something's grossly wrong (and there shouldn't be at this point), you'll get a picture if you just keep at it.

[JesusJones]

Anyone have a spare oscilloscope...?

Ha ha. Yea I've always wanted one but brand new they are not cheap. Used though could prove to be very cheap and useful. And an isolation transformer would just be 120 ac to 120 ac correct? Just stops it from getting a full 15 amps if it shorts out right?


And I looked on fleabay. Would something like this be good enough
http://cgi.ebay.ca/Oscilloscope-B-K-...QQcmdZViewItem

I have 40$ for anyone who has one maybe more...

[nasadowsk]

No, an isolation transformer gives you isolation from the power line, which prevents the chassis from being 'hot'. It serves a very important safety function when servicing series string TV sets, especially when you have test equipment involved.

For a scope, look for an ability to go up to 10 Mhz or higher, calibrated timebases and voltage scales, and a 10V per div input range.

[JesusJones]

Is the way the bottom of the screen is black normal to an extent?

Or could a coil be fried. I checked the orange and green wire coming from the bottom of the crt. (I figured they were responsible for the bottom vertical half of the sweep) Ans it had 700 ohms which I think is right.

Some sort of the other adjustment maybe. Yoke or something.

This picture was taken tuned to a working channel.

The bumble bee was hooked up to pin 9 of v15. The only one hooked up to pin 9 was one that said . 0547. Seems like an odd value to me. Also the .15 and .1 caps to the right of v15. How important are these two caps. Will they make a large impact.

And is there any way to test a cap just with a voltmeter? Doubt it but I figured if anyone knows it's one of you.

[jpdylon]

The condition you see is called fold-over. The bottom part of the vertical scan has folded over on itself causing the black bottom and bright band. Its usually caused by leaky or shorted capacitors, occasionally a resistor that has gone up in value. Look in both the vertical oscillator and output section.

You would have to pull out the cap to test it on an ohm meter. You would also need an ohm meter that put out a high enough current to test the cap for leakage. Since you have to pull it - just replace it.

Trust me on this. Replace the coupling caps in this set and most if not all of your troubles will disappear. I wouldn't even bother to waste your time further. The set basically works - so why not just restore the chassis completely? I don't understand why you might want to have to keep servicing it in the future when another problem pops up from leaving original parts in.

[nasadowsk]

Ok, you've got poor vertical linerarity. No surprise there. I wouldn't be looking at the yoke, yet. That'd be far down on my list.

Rather:

* Go through the vertical section. Replace ALL paper caps, and check resistors. Make sure the voltages into the Vert board are right (+- 10% or so).

* The black bar at the bottom? Centering That's what those centering rings on the yoke do.

* Don't finger the yoke, it's not likely to be bad if it's not open ad the resistance is close to the listed value.

You've got pretty good horizontal and HV and the CRT looks decent.

That bumble bee is a .0047 If it's leaky, it could mess up your vertical pretty badly. The .15 could be a problem, too. The .1's not as critical, but replace it anyway.

The .047 and other caps on the vertical board should be replaced, too.

With these caps replaced, try adjusting the height and lineararity controls to see if you can get thee raster looking right. They interact with each other. Height controls the height, and linerarity controls how evenly it sweeps. In your case, it's going real fast at the top of the screen, and slowing as it gets to the bottom. When everything's right, it'll adjust to be a smooth sweep all across the screen, and the picture will look right.

Once you get all that working good, you can attack the picture issue. Remember, the sweep sections of a TV set use the most power, and if they're not working correctly, everything else is moot.

You said you were getting sound. How strong is it? Is it staticy, or does it 'pop' a lot? With this set, a good strong sound from a TV channel should give you picture, too, unless something's messed up in the video amp's output wiring.

[JesusJones]

Well yea that's why I'm confused. The sound is very strong with the new tube in. I have a very inefficient speaker hooked up to. But the picture just isn't there. I've tried adjusting things till the screen is completely covered then adjusting everything else to get it still. You can not get it still. But the screen can be covered. And can look Grey. But with a channel its all over the place. And you can't see any distinct picture at all. Until you've stared for to long and start imagining.

The sound is not perfectly clear, I guess. But it is descent.

And I have that .15 to put in. So that's good.

And I am curious. The height control. IS(?) it supposed to be 2meg on one side and 6 meg on the other. Because this pot does not check in equally on both sides. Its over 2 megs on one side so my meter says its not connected. Maybe this my problem I already had one bad pot, That caused no HV.

I also found a 22k resistor that goes to the cathode of the 3au6 v12 that only checks in at 15k! And I should have 22000 ohm res.
And I have a 22k resistor. But it's a newer type. The bage very very light brown ones. About a cm long. Can it handle a watt?
Also found a wax covered mica. Real skinny and flat. It shows 00 resistance. So I will start with that and the BB. Also the resistor if it can handle the current.

And any one have a say about that vary pot?

[Old1625]

The area you may need to look at more carefully is the video amp stage. Is there a video signal at the output (plate) of that tube....? If so then trace along the network between there and where the signal reaches the cathode of the picture tube. Possible culprits would be any defective component in the network of peaking coils, capacitors, resistors and whatever.

Also--heaven forbid--is the possibility of a heater-to-cathode short in the picture tube itself. Although in a series-wired set this would likely lead to a raster full of horizontal hum bars....

[JesusJones]

What would horizontal hum bars look like?

That bumble bee cap must have been a replacement or something.(Its the only one in the whole set) It says it is rated at 60000pf If I did it right. (From the point with solder,Blue, black, orange, black, brown) This would be .06mfd.
Which makes me ask again. Is the cap just above v-15(12b4a). Rated at .0547(or is that unheard of) or .0047 as previously stated. I will trust your judgement over mine. And I cut it out already. So I need to get a new one.

So I went to Radio Shack and did not find anything useful. HAhahaha...Figures. But I found one descent thing there. A new voltmeter. This one can test hz and capacitances. Paid 44$ and I'll be able to right it off as a work expense when I start work as an electrician. So score for me.

That bumble be came in at 15 nf. This is wrong. Wrong as can be. So I made a .544 up. With two .022 caps and a .01 :P
I also did the .15
Testy testy time:
Also still wondering about the variable pot. Is it an audio tapered one or something. Because with my new tester it goes up to 500k then on the other side It goes up to 3 megs then says there's no connection, also across the whole variable pot there is 13 meg . Change it? for what?

Minutes later
The picture is still roughly the same. Maybe a bit better. But no sudden people on the screen.
And man you can feel this thing power up. Makes me feel really wack.

P.S. The pot is just screwy. On one side it won't even show 0 resistance . It'll go as low as 315 k then up and beyond 2 megs.