Purchased described as “Has a ROM error“. Started by creating a JAMMA adapter, and then read the EPROM at 2E, it was not found under Romident, burned and installed a replacement. No change. Removed and read all ROMs in row/column 2, and all but one of them failed to be identified by Romident, burned and installed 5 more replacements, working! Still have to wire up an amplifier to correctly test the sound, but looks good so far.
[07/30/03] I finally found the brain cell that got me to realize that I could use my inductive listener (a telecom tool, often used with a tone tracer) to test the sound. It works!
Solution: Replaced bad ROMs
(Recently, the board is starting to develop an intermittent problem with a bad socket. I am going to replace it as the first use of my soon-to-be-here combination soldering/desoldering station.)
Boots and passes self-test, but immediately coins itself up and starts playing itself(!), although not too well.
Well, it looks like some of the inputs are firing rapidly and randomly. Grounding one of the enable pins on one of the 74LS253s seems to make it settle down for a few seconds, so I will try playing with it.
[07/30/03] Update #1: OK, it looks like one of the outputs (za) is always low on the 74LS253, regardless of its inputs. Will try swapping it out.
Solution: None yet.
Random garbage (no sprites) and occasional random sounds, reboots randomly. Clock looks good, CPU and bus address and data lines have what appears to be otherwise normal activity (i.e. nothing appears stuck or floating). Pulled EPROMs and Romidented them; Romident does not identify all but 2 of them, and the two that are identified are not identified as Kicker ROMs!
OK, so I pull the EPROM archive for Kicker, and match them up that way. Three of them match up, four do not. Hmmm… One of the EPROMs does not erase(!). Going digging for a replacement…
Solution: None yet.
Purchased described as “dead”. Started by creating a JAMMA adapter (I hate creating adapters, it is tedious work). Well, the description was correct – she is dead alright: screen has static garbage and required some tweaking to sync correctly on my test bench monitor.
Watchdog is barking, disabling it has no effect on the screen’s contents. Board already had some previous work done in it, solder-side contains more than 20 jumps to connect some RAMs back onto the bus. The Parts side shows the missing/removed/blown traces being jumped.
Started by checking the daughterboard, seems OK. Next I remove, socket and replace the 74LS245s on the board because word has it that they tend to be the cause of most problems, the Galaxian Trouble Shooting Logic Board manuals lists similar symptoms connected to those chips, and the Fluke 9010 troubleshooter says that the address lines are tied. Other than that, I cannot come up with a good way to check them! 🙂
Gotta wait for some replacement sockets and chips to come in…
Continue reading Galaxian – “Dead”
” in corner of screen. Took a look at the Pac-Man troubleshoot by picture guide
and that pointed me to “4R
video RAM bad”. Swapped it, no good!
Tried swapping other RAMs, no change either. Started pulling all socketed chips and found a bent pin on the ROM at 6E! straightened it, and reinserted, Pac lives once more.
That will teach me to try the simple checks/fixes before the more complex ones…
Solution: Fixed bent pin on a ROM chip.
Game would boot normally, but would then start getting random lines/glitches through the screen after running for a couple of minutes; they did not otherwise effect gameplay. Immediately suspect video RAMs, start hitting ’em with the freeze spray and sure enough, got a bad one. Replaced it, and all is well!
Solution: Replaced bad RAM chip.