diagnosing crt tv color problem

Thread Starter

tpny

Joined May 6, 2012
220
Hi, please see attached picture showing a neck board in crt tv. The "G. Drive" and "G. Bias" pots don't work when I turn them - green color doesn't change on screen. Please advice! Thanks!
 

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Dodgydave

Joined Jun 22, 2012
11,277
Compare voltages on the R,G,B pins on the tube and see the difference when adjusting the DC pots, it could be the heater on that gun, ideally you need the circuit of the TV.
 

sheldons

Joined Oct 26, 2011
613
Ok make and model required and I can supply you with a service manual ....unless you start in the correct way you will not repair this fault as colour faults have a number of different causes......it may be nothing on the crt pcb it could be on the main pcb...
 

THE_RB

Joined Feb 11, 2008
5,438
Swap the R and G wires goinf from motherboard to neck board.

If the fault swaps to RED, the problem is on the motherboard. If the fault rermains on GREEN the fault is the neckboard or CRT.
 

sheldons

Joined Oct 26, 2011
613
Again, make and model then the schematics may mysteriously be uploaded...... my all seeing crystal ball has been sent to the cleaners for calibration
 

vk6zgo

Joined Jul 21, 2012
677
Swap the R and G wires goinf from motherboard to neck board.

If the fault swaps to RED, the problem is on the motherboard. If the fault rermains on GREEN the fault is the neckboard or CRT.
You beat me too it!
That's what I always did if one colour was missing.

Beats chasing through tons of circuitry,when you don't need to.
 

Thread Starter

tpny

Joined May 6, 2012
220
It's a toshiba. No marking of a model on the housing. It's like 32" so probably from the 90's.. Thanks for a lot of good guidance above!
 

ian field

Joined Oct 27, 2012
6,536
Hi, please see attached picture showing a neck board in crt tv. The "G. Drive" and "G. Bias" pots don't work when I turn them - green color doesn't change on screen. Please advice! Thanks!
Monitor boards are fairly complex, usually a cascade with complementary pair emitter followers - TVs are *MUCH* simpler, so should be pretty to trace the circuit out by hand.

CRT flashover is not uncommon, so one of the transistors could be S/C - or at least leaky.
 

Thread Starter

tpny

Joined May 6, 2012
220
turns out the transistor for green on the neck board has cracked solder joints with the board, resoldered and green came back, picture looks great!
 
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