GE 14T009 Restoration - Videokarma.org TV - Video

Mre12ax7 · #1 07-16-2016, 03:11 PM

Hello,
I have been working on this GE for the past few weeks but am having a few issues.
So far I have replaced all the old paper and electrolytic capacitors, selenium rectifier , video detector diode and the AFC diodes.
Which has got me to this.
IMG_0235.JPG
As you can see it has horizontal and vertical lock but the horizontal jitters and does not lock in the right place. Sometimes though I can get it to lock correctly (not in picture) but it then goes to this.
IMG_0236.JPG
The picture is now very dim and shrunken in and no controls will bring it back to before, it must be turned off and then turned back on again to make it go back to normal.
This also happens when you mess with the horizontal hold control too much.
My longtime friend at the last radio/tv shop in town has suggested that the flyback is bad.
Does this seem correct? Or should I try different diodes for the AFC (I used 1N4007's).
I really would like to see this work as it is my first TV (I have done many radios).

Electronic M · #2 07-16-2016, 05:26 PM

The flyback has to be at least usable for the screen to light.

Change out of tolerance resistors in the horizontal (AFC/osc/output) section, and see what that does. If yours has SS AFC diodes and not tubes then it is the later version of the chassis, and the hold control should be a potentiometer. There is also an adjustable horizontal oscillator coil/transformer that should be adjusted with a PLASTIC (never use a metal hex key, you will crack the core if you do) alignment tool...Try adjusting that osc. coil for a good synced picture, and then centering the hold control and readjusting the coil.

Mre12ax7 · #3 07-16-2016, 09:03 PM

I have replaced two resistors across the AFC diodes but not the one at the flyback.
It does not have a hold potentiometer.
It uses a hold coil with a plastic shaft that sticks out the back.
The flyback has a spot on the bottom that looks like it almost wants to drip and the wax is bubbled up around that area. Maybe it has a intermittent short?

DaveWM · #4 07-17-2016, 10:20 AM

weak picture poor lock, AGC issue.
as far as the shrink in picture
Have you checked the B+ at turn on and then again as it shrinks. Monitor the B+ and the AC current draw, something like a gassy tube may be drawing more power as it warms up.
How is the HV holding up?
Have you tried new horz out/damper/HV rectifier (SOP if HV or sweep is an issue, must sub don't use a tube tester).

I assume the shrink is there when just a raster as well?
If you are going to do TV work a few must have items
HV prob
neon light for checking fly
Nice thing to have and can be gotten cheap
B&K 1076 analyst good for trouble shooting HV and for signal injection to trouble shoot RF/IF/video issues
Scope for checking wave forms and looking for things like hash on AGC and sync separation issues.
AGC variable DC supply for trouble shooting AGC issues (included on the Bk 1076).

Mre12ax7 · #5 07-21-2016, 03:07 PM

I got some 1N4148 diodes and put them in place of the 1N4007s. No change in the sync issue. Although the shrinking picture and dimness has gone away. I am starting to think that a resistor inside the high voltage cage is drifted and is causing this.

***Eric H*** · #6 07-21-2016, 04:44 PM

In the second picture it's clear the horizontal frequency has gone way off and you have multiple images side by side, something may be shorting causing it to do this.

Have you tried turning the horizontal control when this happens? Sometimes you have to keep turning until it flops over and over until it gets to the right frequency where you have only one image.

If it starts out okay then goes to multiple images then something's drifting or shorting pulling the oscillator off frequency. some cold spray on the components around the oscillator tube might show it up.

Mre12ax7 · #7 07-21-2016, 05:09 PM

Installing the 1N4148s fixed that problem.
It now just has the issue of showing 2 half pictures.
I have noticed some ghosting or noise in the picture the last time I powered it up.
The HV rectifier tube tests bad can it cause this?

Mre12ax7 · #8 07-22-2016, 09:39 PM

I have made a video showing all the problems
https://youtu.be/pSxqS_Wfp3s
As I adjust the horizontal hold you can see that the picture goes almost dark and cannot be brought back without turning off the TV.
I know about the vertical.

Mre12ax7 · #9 08-05-2016, 12:42 PM

I am stumped with this thing.
I have replaced a 100k resistor that I thought was the problem but it is not it.
Could this be a bad horizontal hold control?
FIY: This is my first TV. I've done plenty of radios but not a TV before.

zeno · #10 08-05-2016, 12:59 PM

First thing try a NOS brand name hoz osc tube.
You seemed to have fixed the way off freq problem, now
you have a hoz AFC problem. Check from the diodes
through the osc. Be SURE caps are right value. Usually there
is at least one resistor feeding back from the FBT to the AFC.
Check that stuff also.

73 Zeno

Mre12ax7 · #11 08-05-2016, 01:37 PM

I will get a new horizontal output tube later today.
The one is there is most likely the original as it is a GE branded tube.
I have replaced all resistors in the AFC circuit

Electronic M · #12 08-05-2016, 02:01 PM

BTW I have a beat up version of this set with a restored working chassis and a weak CRT that I've been trying to sell. You could make one real nice one out of two....PM me if interested.

***Eric H*** · #13 08-05-2016, 04:40 PM

Be sure you hooked the AFC diodes up correctly, most are tied together at the cathode (banded end), but not all of them are.

If the vertical is rolling also you may need to go back a stage and check the circuit around the Sync Separator tube

Mre12ax7 · #14 08-05-2016, 05:29 PM

The diodes are in correctly.
Installing a new 12BQ6 made no difference in the lock but I have been unable to get it to go back to the weird thing with the dim and shrunken picture.
I have also noticed when I turn the contrast all the way down the image is more shaky.
The black bar on the screen is about 2 1/2" but if you turn down the contrast there is actually two bars, the larger bar and a smaller one inside it.
Do the lead length of the diodes matter?

***Eric H*** · #15 08-05-2016, 06:54 PM

I am guessing that since the sync signals are carried in the video signal that turning the contrast down is probably reducing the gain and the sync along with it which would make it more unstable at low contrast levels.

I still think it might be a problem with the sync separator circuit, it usually picks off the sync signal from the 2nd i.f. then sends it on to the vertical and horizontal. Anything disrupting the signal from the i.f to the separator could cause these issues, or something at the tube itself could be off.

If both the vertical and the horizontal won't sync then it's likely to be a problem at or before the separator tube, if only the horizontal won't sync it could be something between the separator and the Horiz oscillator or something wrong with the horizontal half of the separator tube. I don't have a schematic so I'm assuming certain things here.