How Many Problems Can You Spot

[vts1134]

After fixing the ion trap in my 630ts I fixed a vertical sync problem and now I am at the point you see below in the video. In the video I start by tapping the front face of the kinescope, then I tap lightly at the neck. As you can see the set does not like this one bit.
I also have a bit of a wave in the picture close to the center at the right hand side of the image.
The kinescope has been rebuilt and displays a much brighter picture than another one that I have. My other tube also has the same picture jumping when I rap on the neck of the tube, but it is no where near as dramatic as this one. The ripple at the right of the image is not present with the other kinescope.
There is a fair amount of picture smearing as well. I think this will be cleared up with an alignment. Some one please correct me if I'm wrong on that.
The picture quality just doesn't seem nearly as good as I think it should be. Maybe this will be cleared up by an alignment also.
Any one spot any other problems that I missed? If this were your set on the bench where would you go next?
http://www.youtube.com/watch?v=6GmMZkNLtS4

[vts1134]

Forgot to mention that the line that moves up the screen starting at about 10 seconds is not in the actual picture, just in the youtube video.

[Eric H]

It has a loose connection somewhere, possibly in that repaired Ion Trap.
It could also be a flaky connection at a tube socket.
You need to start poking around with a wood or plastic stick and see if you can isolate it.

Bad Mica caps in the sweep circuit are also a possibility but I wouldn't think tapping would affect them much.

[old_coot88]

Originally Posted by vts1134

The kinescope has been rebuilt and displays a much brighter picture than another one that I have. My other tube also has the same picture jumping when I rap on the neck of the tube, but it is no where near as dramatic as this one. The ripple at the right of the image is not present with the other kinescope.

From your account and from the video, the first thought is a H-K (heater-cathode) short in the CRT. Does the CRT heater have a dedicated 'floating' 6V winding, or does it run off the main heater supply?

There is a fair amount of picture smearing as well.

A H-K short can cause that too.

I think this will be cleared up with an alignment. Some one please correct me if I'm wrong on that.

Yikes! NO, nein, nyet! Not until alignment is absolutely determined to be the cause of the problem. Undertaking a video IF alignment requires a sweep generator and scope, and a thorough understanding of the procedure.

If this were your set on the bench where would you go next?

I would first eliminate the CRT as the culprit, and go from there. Could you post the CRT area of the schematic, and also the source of its heater supply?

[marty59]

You could install a CRT brightner since it will isolate, and see what happens..

[old_coot88]

IIRC, a regular brightener does not provide isolation. Maybe someone could chime in with a yea or nay on that. But there was an isolation type with a switch so you can set it to provide isolation without heater boost.

[bgadow]

It sure wouldn't be hard to disconnect those heater leads and run it off of something else, even a 6v lantern battery.

[vts1134]

Originally Posted by old_coot88

Yikes! NO, nein, nyet! Not until alignment is absolutely determined to be the cause of the problem. Undertaking a video IF alignment requires a sweep generator and scope, and a thorough understanding of the procedure.

Relax, I don't do alignments on my own . I am not yet at that level of skill and I know it. There is a local shop that I take the set to and he walks me through every step of the way. The last set I did I wouldn't have thought it needed alignment, but I was shocked how much better the picture looked afterwards. The alignment will be the last step on this set. I have to have everything else nailed down tight first.

Originally Posted by Eric H

It has a loose connection somewhere, possibly in that repaired Ion Trap.
It could also be a flaky connection at a tube socket.
You need to start poking around with a wood or plastic stick and see if you can isolate it.

Bad Mica caps in the sweep circuit are also a possibility but I wouldn't think tapping would affect them much.

I'll get tapping as soon as I can .

Originally Posted by old_coot88

From your account and from the video, the first thought is a H-K (heater-cathode) short in the CRT. Does the CRT heater have a dedicated 'floating' 6V winding, or does it run off the main heater supply?

It runs from the main heater supply. One thing I don't quite understand is the schematic looks like the heater and cathode are tied together. Wouldn't that would mean the heater and cathode are constantly shorted? What am I missing?

[old_coot88]

Originally Posted by vts1134

..It runs from the main heater supply. One thing I don't quite understand is the schematic looks like the heater and cathode are tied together. Wouldn't that would mean the heater and cathode are constantly shorted?

Right you are, amigo. That precludes an H-K short. That's why i wanted to see the schematic. In later designs, video was fed to the CRT via the cathode; whereas in your set, it's fed via the grid, with the cathode grounded.
So the mystery deepens.

Other than the CRT, do other parts of the chassis show sensitivity to probing/tapping?

If the CRT remains the prime suspect, it might be an open/intermittent G2 (grid 2).

[Geist]

Hi All;
VTS1134, It also could be that the CRT leads need to be resoldered and or checked for good connection or wiring breaks.. Check out Bob Andersen's site for how to check out possible crt connection problems and reflowing of crt connections..
THANK YOU Marty

[Username1]

You need to tap many components, especially tubes, and do it very lightly to find the most sensitive item to cause what you see. And be sure to check the picture tube ground. Move wires around etc. I would bet its not the picture tube.....

When you tap the tube, the black gets blacker, so I would go to Contrast control, video amp, AGC, H Sync, IF.

Is the sound effected by the tapping?

[vts1134]

Problem solved. The solution was far less exotic than I ever thought it would be, but isn't that almost always the case?
The BNC connection on the lead wire to my B&K analyst is shot. Tapping on the tube was shaking that wire which was causing the problem.
Onward!

[Tubejunke]

Although the problem has been solved, I wanted to add that the RCAs of around that era, and maybe others had a short grounding spring that must make contact with the conductive (aquadag/spelling?) coating on the crt bell in order to produce a raster. Just something to remember, or for others to note.