WG P738 / U5000 Color Troubles

Arm123

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I have a WG P738 / U5000 in a Blitz 99 thats giving me some issues. Started out displaying just red that progressively got worse when the screen started to flicker to a solid whitish pink / purple color. The monitor is now stuck on that.

All the breakout board controls respond, so i am assuming its not anything in the vertical / hrz deflection area.

I went threw the neck board and resoldered all the lifted traces i found around Q503, Q504, Q505.

I socketed and replaced U500, no change.

Also tested all the smaller amp transistors (2n3904) and resistors in the color circuit and they all test as fine.

I do have one small question... that may have been caused by my stupidity.

I noticed on the main board, mounted to the heat sink of U601, there is a resistor thats mounted to the heat sink. It has a couple of leads, one white lead thats connected to a 2 pin plastic connector which is connected to TP205 (30V).

I may have disconnected it by accident and connected the empty socket of the connector but i cant remember. The white lead is supposed to be connected to TP205 ?

Any other suggestions ?


Thanks for reading.
 
When you say "just red" do you mean a red hued picture, or just solid red?

Could be a shorted gun

Could be a shorted red transistor

Not (probably) related to your problem, but I always like to check R811 to see if its gone open, it can cause all kinds of color issues (probably not this one, though).
 
Hey there, thanks for the reply.

I hooked up the rejuvinator to the tube and the guns check out fine, no shorts.

Just check R811 for fun... its ok at 100k

Any chance i can get you to look at the heat sink of U601 ? just let me know if the white lead is connected to TP205
 
Couple things i noticed...

The remote board has P718-D marked on it but the chassis says its a P738. Are the remote boards swapable for those models ?

The B+ starts out at +147v and then drops to about +142v once its been on for a bit. I do know that its supposed to be at +156v according to the voltage reference manual. The B+ knob is glued down... Should i play with it ?
 
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P718-D is the correct remote for a U5000. You can swap it with the one from a U2000 and it will work....
 
Well Peale, it seems you may be right about the tube short...

I hooked up the rejuvinator and the guns all 'looked' really good (way green) and there was no short lights on... There was a bit of heater leakage, but thats not too bad.

For the hell of it, i decided to hit the guns with with a 'clean and balance'. I started to hit the red gun and saw that the meter on the green gun go way down... I have seen this happen before on a tube that has a G1 short. Same thing happened when i hit the green gun, the red gun would go down / jump.

The only gun that response well is the blue gun.


What can i do ?..
 
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