Vectrex hardware repair question.

[dabone]

I'm working on a unit with a single horizontal line, and checking voltages, I have no ground on the CD4066 @ IC305 and the MC34004 @ IC303.

Any suggestions to start with?

 

Thanks.

Later,

dabone

 

[+KylJoy]

Does it make sound, etc.?

[dabone]

Yes, movement on the line, and sound.

 

Just missing ground on part of the main board.

[+-^CrossBow^-]

Yikes...with the monitor being vertical mounted I'm guessing that is a vertical collapse condition then. Not sure right off hand but I would guess an IC somewhere in the Veccy is responsible. Although I did have an arcade monitor with a similar condition and it was an issue with the tube's actual deflection being the problem and I ended up having to replace that tube out since it kept blowing chassis boards all the time. Not saying that is the case here, but just my experience with something similar.

[dabone]

Ok, I was chasing the wrong thing with the ground issue. Didn't realize that that section used a different voltage.

 

I found this on the web...

 

 

"You can also get a slightly different display if only the Y-axis side of the LM379 has failed. In this case you still get normal sound. The display will show a single raster line centered vertically on the screen. In other words you will only see a single line reaching from the right to left side of the screen. Typically this line will have 'dancing dots' on it as objects are being drawn to the screen. You get this display instead of the blank picture as before due to the deflection detection circuits that enable J-FET's 401 and 402 are only taking their sense signal from the horizontal deflection. "

 

So, I ordered a nos lm379s from ebay along with a cap kit, replaced both, and now I have this display instead of the single flat line.

 

Any thoughts? I'm wondering if the lm379 I got was wrong.

 

 

 

 

Thanks.