Asteroids G05-802 problem I can't figure out

liquidx

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I have a G05-802 monitor that's driving me mental, maybe someone here can help.

I have a working asteroids game board, it plays fine on the scope (also when getting the signal from P100)

I had problems with the monitor losing horizontal deflection and the spot killer coming on as well as chassis transistors blowing and even though I went through every single component and checked the input voltages (steady 95v coming in to P500 etc) I still couldn't get it to work.

Anyway, I just got a new working/tested deflection PCB as a comparison/reference point, hoping that would help me see what was wrong and, in any case, finally get the game playable.

When I plugged this new PCB in, the spot killer was on and I had no horizontal deflection. I can logically deduce from this that my problem is outside the PCB.

Powering it up a second time to take some readings, the spot killer was still on but I'd lost the picture, turning brightness/contrast up only produced a faint haze towards the top of the screen.

Looking at the PCB, R713 was burnt to a crisp. So I gave it a closer inspection and found Q705 and Q706 to both be shorted. I checked the chassis transistors, they're fine, I looked for shorts in the sockets, plugs and cables leading to them but found nothing wrong either.

Grounds seem to go where they should also.

The vector FAQ talks about a white haze on the screen being linked to HV failure but it was measuring fine before this (including a good 12KV).

As the 3 components that blew are neighbours, I've been trying to trace back from there for a source but I can't figure out the problem (with my limited knowledge anyway).

Any pointers would be much appreciated (by my girlfriend too who's been playing it on the scope :) )

Thanks!
Colin
 
Verify that you have +/- 30vdc at P600 pin1 & pin7 and P700 pin1 & pin7.

Missing +/- 30vdc at the above location, verify the +/- 30vdc at the input side of R100 & R101.

Still missing, verify DB100 (BR) is good.
 
Verify that you have +/- 30vdc at P600 pin1 & pin7 and P700 pin1 & pin7.

Missing +/- 30vdc at the above location, verify the +/- 30vdc at the input side of R100 & R101.

Still missing, verify DB100 (BR) is good.


I'm actually picking up +/- 45vdc at the P600/700 pins, which seems a little high to say the least.


Colin
 
Hmmm, I think I would verify all voltages as per the transistor table in the FAQ to see if I could find where it goes bad.
 
Hmmm, I think I would verify all voltages as per the transistor table in the FAQ to see if I could find where it goes bad.

Well, when I power it up now, I blow F700 and/or Q708 & Q709. Which makes checking voltages a bit difficult.

This happens with 2 different deflection PCBs.
That's what I don't get, I had this problem already. Installed a known working deflection PCB into the monitor and got exactly the same symptoms. What, outside the board, would make this happen?

I'll try and check all the voltages without blowing more components. I'll be out of spares soon :)
 
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