Burnin' Rubber ( Bump 'n' Jump ) repair
palindrome:
Display would start acting up after a few minutes of game play then symptoms would completely disappear after 10-15 minutes.
An obvious intermittent fault due to heat.
Symptoms: Grey vertical lines mostly around sprites but also affected other areas of the screen.
Troubleshooting: Cooled off suspect chips ( I used some ice wrapped up in a plastic bag to avoid any leaking ) and found cooling the transistor @ Q4 on the video board would reproduce the above problems.
Fix: Replaced the faulty 2sc1815 transistor at Q4 on the video board which cleaned up the video sync signal.
channelmaniac:
Nice fix!
Namco Classics 1 and 2 have the same video issues at times, but those are related to garbage capacitors that need to be replaced. :)
palindrome:
Still one more issue to fix on this board which I'll post the solution to once I find out the problem.
Game runs most of the time when switched on, other times it doesn't start at all. So when this happens address pins on the 6502 are all stuck high ( 0xFFFF). Everything else looks fine via logic probe.. RST is high, R/W is high, RDY/IRQ/NMI are all tied to 5v and CLK is pulsing although I don't have a scope to see it clearly. It's a Synertek 6502, I tried swapping the sound CPU ( A Synertek as well ) but same issue.
Strange problem for sure.
channelmaniac:
Watch the reset pin with a logic probe. It's probably not working properly. Could be as simple as a bad cap in the reset circuit. Replace C49 and C48 and see if that fixes it.
palindrome:
I'll give that a go. Thx.
But I suspect the LS04 at 9C to be flakey.
Pin 8 on the LS04 is completely dead ( floating ) whenever I observe that fault. So I believe there is no trigger to start the 555.
I will replace LS04 and hopefully that will fix it.
Navigation
[0] Message Index
[#] Next page