Can't find my book!
 

I have one of the books that helps you diagnose a tv by the issues on the screen , like foldover.
Well, I just moved and can't find it...
OK, that leaves me two questions.
First I have a set that has both dark and bright (compared to the rest of the picture) lines on the left side of the screen that start at the top and work their way down but not all the way down the screen. they are just darker or brighter than the rest of the image. My phone just does not want to get a clear image of it or else I would post it.
Any ideas? I did put a new yoke in this set and removed the caps in it because it's directions stated to install exactly like the original. I am not sure if this is a cross talk issue but it seems to have kinda just started and seems to be slowly going farther across the screen.

Second, I remember reading about ( I believe) inter element capacitance in the crt itself that required a neutralizing cap to be installed between the grids(?) under the chassis.
Anyone know about this issue?
On my set I did tip it over on it's side when it was running so I could check voltages and after that I did lose the picture. Since then I had to put the ion trap on the other side of the crt neck and it will not show a picture with the trap on the original side.

This is not my area of expertise, so I cannot help. You may get more responses if you can change the title to something like "Yoke problem on RCA 16-inch model xxx" or similar, I would think.

The first problem, is you don't say what era TV you have, or make and model and that prevents anyone from giving you specific instructions.

The left side picture defect sounds like Barkhausen. I say "sounds like," because a picture surely would help to confirm this. There also is a pretty good chance that you will invent a new cuss word before you find the cause!

The cause of this defect is electromagnetic radiation (or rarely electrostatic radiation) from the horizontal sweep that is being picked up somewhere between the antenna and video signal to the picture tube. Since there is a time delay here while traveling though the circuits the second time, the spike or spikes are shifted into the picture.

The below is general procedure for 1940 to mid-1950s electromagnetically deflected TV sets:

The usual cause for this is any tuner, IF or video tube that is missing its shield, or the shield is not properly grounded.

Or, the antenna lead is not shielded or possibly dressed too close to the horizontal output tube, the flyback or HV lead.

Or, if the antenna input is coax and the center and ground connections are reversed, as with a balun coil connected wrong. (This problem usually will come and go as the cable is moved.)

Or, the HV cage is missing or not properly grounded.

Or, aquadag coating is not grounded.

Or, HV lead not fully seated in the CRT.

Or, a current limiting resister in the HV lead is breaking down.

A remote possibility is lack filtration in the control circuit if your set has AGC keying.

On string filament-chassis, a heater cathode short can cause this.

Usually not, but I've seen gassy or slightly shorted tubes cause this. When all else fails, substitute one-by-one all tuner, video IF, AGC, and video amplifier tubes.

Now here is the kicker! Sometimes it goes away for no apparent reason, and only reappears when you clean up and put everything back together!


The second defect, having to move your ion trap, sounds like something such as the CRT, the yoke assembly or the focus assembly or focus coil shifted when you tipped the set.

Your two defects probably are not electrically related. (An exception to this might be if the current limiting resistor in the HV lead is failing.)


James.

thank you for your response. this problem is once again my 1949 muntz set. to be honest this set seems like a lemon and has been one problem after another. just pure frustration. i will check the things you mentioned. I just want to be done working on this set!

I had one set (a Hallicrafters T-67) with a textbook case of Barkhausen oscillation. It made a squiggly vertical line in the left portion of the screen, which was otherwise normal:

http://antiqueradio.org/art/hallit-6708.jpg

The cure, which is the first one recommended in my old TV books, was to substitute the horizontal output tube.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

thank you! I really do not like posting new questions about the same set over and over, makes me feel like like a forum hog!.
tell you what though, this set has been a real teacher since with help from this forum i have had to figure out a multitude of issues!

Radio nut,

If you had added this symptom to one of your previous posts, that might have informed the rest of the forum what general vintage set you were working on and what you had done previously.

As for Phil's tube substitution suggestion, yes, that is the thing most books suggest because it is the easiest thing to do. With that said, I've found that it usually is not the problem if one has done the standard visual inspection of an improperly working set.

This would include visually inspecting the horizontal output under reduced lighting for either a pink glow on the plates, or a purple glow shining out from inside the plates. If so, replace the tube. If the problem seen was pink plates, immediately check the difference in the grid voltage and cathode voltage to determine why the old tube overheated from pulling too much current or you will fry the new one in short order.

(Tubes with a purple glow may be used as long as they work properly without causing a problem, when confirmed by substitution. Sometimes, if you catch the pink plate issue quickly enough and the cause is a fixable under the chassis component, the overheating tube may be salvaged, too.)

It is very rare to find Barkhousen caused by a horizontal output tube that is not showing these symptoms.

The pink plate problem can happen to any tube, and should be the first thing you do at your first power up of the recapped set! It is as basic as smelling for overheated parts. The most common in 40's & 50's tubes suspected of having this problem, in order of probability, are Rectifier, Damper, Horizontal Output, and Audio Output.

James

If I remember from a long time age, putting an ion trap around the horizontal output could stop barkhausen also.

Well, I tried taking pics again, and with my phone I cant get a real good image but I will kep trying. I subbed in The Hot ,and high voltage rectifier and had to readjust horiz. hold but noticed a cleaner picture. found a nos damper put it in and now the problem is changed a little. There is about a 1 to 1.5 inch darker than the rest of the picture bar on the left and everything in it is fuzzy and magnified. when a person walks across the screen their shape changes. I will see about putting the original damper tube back in and see what happens and borrow a digital camera for pictures.
I did make sure that the high voltage lead to the crt was tight and the ground to aquadag finger was snug on the crt also

Radio Nut,

Did your original symptom look like Phils' very clear photo above?

In it, there is no shading, just two vertical lines.
There is no image fold or magnification (stretch).
The left side vertical lines may be speckled or they may be black or they may be white or a mixture of the three.

If not, you did not have Barkhausen!

This tube switch reduced the Barhausen, but created a new problem that I underlined in your reply. Correct?

On your circa 1950 Muntz, you have four controls grouped together on the right side of the back of your chassis. The bottom left of those four is the Horizontal Drive trim capacitor . (One side of the trim capacitor is grounded and the other connects to a 100 ohm resistor going to pin 5 of the 6BG6, a 470K resistor going to the ground and a small capacitor going to horizontal oscillator transformer.)

Did you turn this trimmer capacitor before the fold problem appeared? If this not the same problem you had before the tube swap, try adjusting the trimmer with the new tubes in place.

A single horizontal fold is usually horizontal drive, that adjustment. The fold may be on the left, but more often is near the center of the screen.

Adjust the trimmer for least fold (and best linearity), while measuring the voltage ground to cathode on the 6BG6. You want that adjustment to be on the side of the range where there is the least voltage on the cathode (in other words, with the tube drawing the least plate current.) The need for readjustment is not unusual when replacing the Horiz Output tube.

There may be other causes, but an incorrect drive setting is the most common.

James

Mine IS shading and image distortion, but I just realized what " might" be the cause.
In the high voltage cage is a chassis mount resistor that went bad. I installed a high wattage brown resistor in there and it is just kind of sitting right next to the damper tube. It can be bolted to the chassis but since there is not a hole in the metal near by I did try to solder it to one of the old chassis mount resistor pins but the solder will just not take to it.
the end result is it is very close to the damper tube. I thought about putting it under the chassis but do to its heat I figured it would be better left in the high voltage cage. If I can get some sleep I will move it around and see if it helps or makes the problem worse. The horizontal hold is what needed adjustment after tube swap.
I did readjust the horiz. drive and it does affect the picture but not this issue.
From an earlier post I noted that I had lost the shut off dot, since the tube swap it is back.

Lets see if this pic helps!

The real bright line running at an angle is just from the phone.
Above the quilt square on the left you can see a dark line and on either side it is brighter. The wide darker line from my earlier comment went away once I pushed the resistor over a little farther from the damper tube and pushed extra wire back under the chassis.
I am now wondering how sensitive the damper tube is to items near it.

For the heck of it, i would try putting the components back in the yoke that came with it.

The factory schematic for the Muntz 17A2 (Rectangular 16 inch CRT) shows no capacitors in the vertical yoke, but one 56 pf across the horizontal winding that is between the center connection and the Flyback.

Why did you replace the yoke?

If the yoke was shorted when you got the set, there is a possibility that the previous service person trimmed the capititor out, to confirm that the yoke was bad and not the capacitor. Doing that was SOP back in the day before the shop plunked money down for a new yoke. They were not returnable if installed. Most people junked an older set rather than pay what a new yoke installed would cost.

The vertical squiggle (vertical ringing) in the horizontal lines on the left edge indicates cross talk from some to be determined source, the yoke is one possibility, and another are the electrolytic capacitors. You did replace them, didn't you?

I am agreeing with Old Coot here the cap in the yoke.

Also, redress the position of the resistor and leads to as near where the old one was. When you have drilled out the old one, use one of the holes to mount the new one. (Don't to this and the capacitor test at the same time, or you won't know which worked. It makes no difference which you do first, but leave the first in while you do the second.)

James

the picture on the set originally was focussed on the left side and not the right. no matter what I, did the picture was fuzzy on the right side. I replaced the yoke, and this is when I stated when I tried to lay the set down it dropped ...I put the new yoke in and ..no picture, at all. I pulled the caps out of the new from Meyer's yoke and still, no picture. That is when I had to start putting the ion trap on the other side of the CRT neck to get the picture.

the electros are new, formed 450 volt caps. the diagram calls for 500. thats part of the reason I put a voltage dropping resistor in the power cord to keep the b plus as close to diagram as possible which may still be too high in the long run. my diagram is in my car and my wife has it. i think the b plus line should be 370 or 390 ish.

Here'ya go!
 

Let The Pep Boys help!

http://i125.photobucket.com/albums/p...ps337d3992.jpg

http://i125.photobucket.com/albums/p...psf093f8ca.jpg

when I first got this set, The 16rp4 that was in it did not have an aquadag or a springy finger to ground the crt coating to the chassis. I did have a thread where I asked where did the shutoff dot go?.
Checking things that members have suggested to check now I found that my different 16rp4 has the aquadag worn down to the glass by the springy finger that I bolted in .
I moved it to a different spot and that probably is why the shut off dot is back again.

My new yoke does NOT have ANY cap in it.....So lets see, I pulled out the one that I need? That makes sense on my part!
I pulled them When I did not get a picture after the yoke was installed, thinking that they were keeping the yoke from working correctly, It did not occur to me that maybe I jarred something loose by dropping the set which caused me to need the ion trap on the other side of the crt neck.

I replaced the original yoke because the right side of the picture would not focus but the left side would, no matter what I did. now the picture is uniform all the way across. in my opinion it is a little fuzzy but my wife said its fine.
I do need new glasses ..... so maybe she is right but the last time I checked the 500,000 ohm resistor in series with high voltage crt line it was about 780,000 ohm's. so maybe that needs replaced. I have avoided that one do to the space below the 1b3 socket and the fact that even at my age my hands shake..........especially working in tight spots!
If I am correct low high voltage can cause out of focus condition.....but I will even admit that sitting away from the set it does seem clear, just not as clear as other sets I have owned. these sets were ...well....higher quality Motorola or RCA units

I checked my diagram (Muntz M31 ,sam's set 108 folder 8) and my set does not have a 56pf cap that I can find from the center horiz winding and the flyback. Maybe I need one? My set also uses the alternate horiz. damper circuit listed off to the side.
Mine is chassis 16a2.

well lets see, I replaced the resistor mentioned earlier and it is away from the damper tube. Problem still there,
I wondered about the crt itself since it got bounced around. nope, replaced it and problem still there. I pulled the video out tube so the set would be raster only and the lines are still there....that was also without any signal. I am going to get new electro's that are 500 volts soon.
just asking......I thought bad or leaky electro's would put lines all the way across the screen or a wavy pattern indicating 120 cycle hum?
Plus earlyfilm had wanted to be to check for the cap in the yoke....should I just put one in or jumper in temporarily for testing?

I have checked pretty much everything mentioned at the top of this post...subbed horiz. out tube,damper and high voltage regulator. I forgot about the high voltage current limiter resistor....Any way to just check it besides resistance value? or should I just replace it.?

I would "IF" I kept them or the original directions with mini diagram so I knew what to add to which pins in the yoke.....
And I normally keep the box and directions and just put extra caps or nuts and bolts in those boxes but this time I threw everything out because that would be too easy!

Oh, The horizontal linearity coil is nos and just like the original makes zero difference to the picture no matter what I do with it. I have run it all the way in and out slowly while watching the set and.......nothing.

I was able to get a hold of Moyer's electronics where I had purchased the yoke and they will copy and e-mail the mini diagram for the yoke so I will be able to buy/install correct cap or caps for it.

Well today I installed the correct value parts in the yoke for the ones I removed to make the new yoke match the original one (50mmf cap and a 1000 ohm resistor in series) and the problem in my opinion is worse. It (if I am correct) seems to get worse every time I turn it on, but it is sitting all week unused. OK, So next time I will put in fresh new 500 volt electro's and A current limiting resistor in the high voltage line and see what happens.

Well,I bought 600 volt electrolytic and installed them. The problem is less obvious. I did form them on a healthily for a couple of minutes butt that can't be a s good as running the set. I will see if the issue goes away after the electrolytic capacitors settle in to their new home.

Manny, moe, and jack make one of those for flat screen LCD tv's....?

.

Well, the problem is better, but still there, one thing I am curious about...
the horizontal width is cap controlled and now I am thinking about subbing a different one in and seeing what happens.

Well, hope this is the last muntz post from me but here goes.....
In the damper circuit i subbed in a .1 cap instead of using a .047 and the width is better and the lines are no longer there..... thanks everyone who replied to yet another Muntz post of mine! So the picture is solid with a very wide range of contrast and very strong loud sound but as earlier mentioned this set is a table top mounted on a hom made bottom making it a console and they used a 10 speaker there and there is a 5 inch one mounted up top.
Now that i am done....i really am thinking about selling this headache!
Already have a buyer.......