View Full Version : G.E. 800C problem


Phil
08-15-2016, 04:59 PM
Hello everyone,
I have a G.E. 800C I restored to operation about a year ago and have been regularly watching it since. I few weeks ago when I turned it on nothing happened and I found the picture tube heater open. I had a spare tube so installed it. To the best of my knowledge this tube is good. I think I tested it in the set when I bought it but I can't remember for sure. Anyway, I get no sign of life on the screen unless the focus coil (sliding, swinging type) is moved almost all the way forward. Then I get a fairly dim "picture" which could best be described as blobs of varying contrast moving around the screen. The HV measures 7.1 KV. Is this low enough to cause the problem? The service information doesn't say what is normal although the datasheet on the 10BP4 indicates typical operation is 9 KV. The television was working very well with bright, sharply focused picture prior to the death of the 10BP4. I'm a bit baffled as to why the picture tube heater opening up would cause anything else to fail.
Any insights would be appreciated!
Thanks

bandersen
08-15-2016, 05:13 PM
Have you tried moving the ion trap magnet around ? Perhaps the CRT that died was a 10FP4 which doesn't require one ?

Phil
08-15-2016, 05:42 PM
Thanks for the reply. The tube that died was clearly marked 10bp4. The replacement is
Not very clear. It might be a fp4. I have tried moving it around. I'll try removing it altogether and see what happens.

Phil
08-15-2016, 08:04 PM
Removed the ion trap and got nothing at all on the screen, so apparently not a 10fp4

bandersen
08-16-2016, 10:31 AM
Does moving around the ion trap magnet have an effect ? It needs to be positioned correctly to get a bright, clear image. Also, have you tried flipping it around ?

dieseljeep
08-16-2016, 11:43 AM
Does moving around the ion trap magnet have an effect ? It needs to be positioned correctly to get a bright, clear image. Also, have you tried flipping it around ?
The blue sleeved side of the double ion trap should face the focus coil or magnet.

Phil
08-16-2016, 03:03 PM
Thanks for the suggestions. I've moved the ion trap all around but haven't changed it's direction. The service information says to make sure the trap is pointed the right way IF you have the two magnet trap. This set has a one magnet trap so I stupidly assumed it didn't matter. There are no markings on the trap, such as an arrow, to indicate which directions it should go and the whole thing is black, nothing blue anywhere about it. I'll try turning it the opposite way tonight and see what happens.

bandersen
08-16-2016, 04:19 PM
Strange, a 10BP4 should have a double trap magnet. I wonder if the original CRT was a rebuild with a gun only requiring a single trap?

A dual trap magnet looks something like this.
https://c2.staticflickr.com/3/2653/5821883785_e602e65489_n.jpg (https://flic.kr/p/9SsFdD)

Eric H
08-16-2016, 05:36 PM
Looking at the Schematic, the type of trap used depends on the type of focus coil.

Seems like a 10BP4 would require a double trap regardless, unless it uses the focus coil for the second magnet?

In any case all you did was change the tube for the same type so it should be right.

http://www.earlytelevision.org/pdf/ge-800-rdier-tv4.pdf

Username1
08-16-2016, 06:34 PM
Hello everyone,
I have a G.E. 800C I restored to operation about a year ago and have been regularly watching it since. I few weeks ago when I turned it on nothing happened and I found the picture tube heater open. I had a spare tube so installed it. To the best of my knowledge this tube is good. I think I tested it in the set when I bought it but I can't remember for sure. Anyway, I get no sign of life on the screen unless the focus coil (sliding, swinging type) is moved almost all the way forward. Then I get a fairly dim "picture" which could best be described as blobs of varying contrast moving around the screen. The HV measures 7.1 KV. Is this low enough to cause the problem? The service information doesn't say what is normal although the datasheet on the 10BP4 indicates typical operation is 9 KV. The television was working very well with bright, sharply focused picture prior to the death of the 10BP4. I'm a bit baffled as to why the picture tube heater opening up would cause anything else to fail.
Any insights would be appreciated!
Thanks

I wonder what could have happened to cause the picture tube heater to
open, Might be a better question....... You may have experienced some
type of intermittent short in the series line that may have caused the
filament string to get a bit of a boost when you turned it on, and the
crt turned out to be the weak spot......?


Could be something waiting to fry another crt, or nothing at all......
Possible heater cathode intermittent in some tube, cap to ground
in the heater string somewhere, bare wire, poorly soldered wire....?

.

Phil
08-24-2016, 04:36 PM
An update: It seems the focus coil in versions of this set with the swinging focus coil (vs. the clamped coil) apparently does serve as the second magnet of the ion trap. Adjustment affects brightness, centering and focus all at the same time. Its usually quite easy to find the right spot for it. Anyway, I turned the Ion trap around 180 degrees and now I have a decent picture! I guess i've always been lucky in the past and happened to put them on the right way by accident. Now I just need to get the HV back up to normal and all will be well. Thanks to everyone on the forum for your help.