Millipede PCB repair

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

I am attempting to troubleshoot my millipede board. I am testing this
board with the arcadeshop converter for a centipede cab. Here are the
symptoms thus far.

1)All voltages are present and measured correctly. Cabinet plays a
centipede board with no issues.

2)All chips have been reseated with no difference.

3)Blue full screen square is visible on screen when power is applied.

4)Switching game into test mode makes makes minimal difference. In
text mode screen looks the same but a clicking noise can be heard
coming from the speaker. I would say clicks are a second apart.

5)No beeps can be heard.

What is my next step?

My ideas are:
1)Bypass watchdog by grounding WD test point to see if beeps appear.

2)Replace first 2114 RAM and see if a bad first RAM prevented beeps
from starting.

3)Ask newsgroup in hopes that someone with more knowledge than me can
help!

Please help!
Phil

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

ive gotten some good emails on this issue and wanted to update the post
and see if anyone has any information.

1)I acquired two untested pokeys from a dead board I have and another
6502 CPU. When both both pokeys were replaced with these pokeys.
different video came on the screen. They were reseated and the game
seemed to boot into test mode briefly. I could see P0 and P1 on the
left side of the screen indicated that both the pokeys were reading as
bad. Moving the trackball and pressing the start buttons caused the
board to leave test mode and shows a white series of dots flying
vertically in the center of the monitor.

2)Disabling watchdog makes the screen go black but does not produce any
beeps.

3)Different combinations of teh pokeys and CPUs leads to different
garbage behavior

4)In one configuration, the lower start button would blink if i pressed
on the area of the pcb with the cpus and pokeys.

5)Why would replacing the pokey change the video on the screen, i
thought it was a sound chip?

6) the click from my first post has gone away. i dont know why.

My hunch is that the sockets are bad and I am in the process of
replacing them right now. Does anyone have any other suggestions? Im
sure I have bad pokeys, and possibly RAM, but i would really like to
get to the test modes before i go replacing things at random.

Thanks for any help,
Phil