Space Invaders Deluxe board, jittering garbage on screen

[DaveyPocket]

Space Invaders Deluxe board, jittering garbage on screen

I'm repairing one of my Space Invaders Deluxe boards, and I'm not able to figure out what the problem is.

(Picture is attached)

This is what is shown when the board is installed in the machine and ALL of the ROM's have been removed. From what I've read, if the ROM's are removed the screen should only show horizontal bars and maintain a stable picture. When I remove the ROM's or leave them installed, a similar issue occurs (the ROM's do work, I tested them in my other board). The screen shows garbage that moves toward the left. At the far left of where the garbage is shown, it sort of jitters upwards and downwards. The screen garbage does not cover the entire screen, and there are some sort of faint noises coming out of the speaker.

I've tested the sound board on my other machine, it works fine except for the alien explosion sound which is missing. Does anyone know of anything that could be causing this problem?

Thank you

 

[Kawydud]

Almost looks like what my original space invaders is doing. Not sure if the tests are the same for the power supplies, but check here to see if your power supply looks like this. My reset line voltage is high, 2.4 volts instead of .4. I have also been told that the slam switch can cause issues as well.

Voltage test - http://elektronforge.com/TestMdwPS.htm

 

[KevinMullins]

Check power supply voltage and rest line as suggested.
Have you tried the test ROM for Space Invaders?
Check CPU and ROM sockets.
Read up on grounding pin 7 of each RAM and look for changes. (we have several threads discussing it somewhere)

 

[orion3311]

Yeppers once again a reset line problem, try grounding the reset line which is located on the plug going to the daughterboard. (the one thats NOT the control panel plug).

As for the missing sound, if you look here: http://www.brentradio.com/SpaceInvaders.htm there's an article that talks about missing sounds. Basically SI (and SID) use individual circuits for each sound, and supposedly the LM chips go bad a lot on those.

Thread should be moved to general repair - if you search in there we have Kawydud's thread already covering the exact same symptom.

 

[DaveyPocket]

Thread should be moved to general repair - if you search in there we have Kawydud's thread already covering the exact same symptom.

Yea, I accidentally posted this thread under here, I will move

 

[DaveyPocket]

I tried grounding the reset line on the power board and on the daughter board, no change. I applied +5v then ground, no change.

The current reading of the reset line is around 0.24 volts.

I tried grounding pin 7 on all of the RAM's, garbage goes away and is replaced with thick vertical bars with narrow gaps, still moves left and jitters vertically at the end on the left. Still makes noises from speaker.

P.S. - I don't know how to move threads to another section