Today ‘coolmod’ sent to MAME Dumping Union mailing list the dumps from his Dead Connection PCB (two layer Japanese revision on Taito F2 hardware).Dumps were obtained from two PAL16L8 devices so I took care of converting them to GAL16V8 format.Replacements have been successfully tested by ‘coolmod’.Thanks to him for this contribution.
Some days ago I bought on Ebay for cheap an untested original Sega Pengo PCB, today it arrived:
Buying a board as untested is always risky, you could ended up to have a not working one on hand and indeed mine was.I was greeted by a solid black screen when I powered it up, the main Z80 CPU didn’t reset properly.As schematics suggested the /RESET is generated by a counter 74LS161 @IC23 so I went to probe it and found it was missing clock signal.At this point I started to suspect some trouble in the timing signals generation.The Pengo manual has a troubleshooting section which suggests to check some iC in case the picture will not appear:
When I went to probe a 74LS74 @IC66 :
I found its outputs pin 5 and 6 were stuck high.I put a my fingers on it and it was really burning hot.Also comparing it against a good one with my HP10529A logic comparator confirmed my suspicions:
Once removed, the IC failed the out-of-circuit test:
Fitted a good IC fixed the board completely, no further issues were found.
Today our member Corrado sent in the PAL dumps from a Sengoku Ace PCB.They are all tested into GAL16V8 targeting device.Thanks to him for this contribution.
Today some addition to our PAL database.With courtesy of user ‘tinhead’ on the EEVBlog forums we can host his recreations of registered PLDs found inside the Hi-Lo Systems ALL-07A EPROM programmer (which I personally use).You can read more about here:
https://matthieu.benoit.free.fr/hilosystem_all-07_universal_programmer.htm
Speaking about arcade PLDs, I successfully reversed into a GAL18V10 targeting device the dump made by Porchy from the PLS153 marked ‘315-5298’ found on some Sega System16B ROM boards (171-570 and 171-5521).
I had this rare Irem Ken-Go PCB (an undumped version included in latest MAME release) from my friend Joachim for a repair:
The board played fine except for an issue where all sprites were formed but missing all colors appearing like black shape:
Sprites generation circuit is located on top board where some customs lie:
Documentation for this specific game was not available but luckily I could know function of the various customs by looking at the R-Type schematics and so identity the one involved in the sprites palette generation:
The custom itself was marked ‘KNA91H014’ in 60 pins QFP package:
Probing it revelead that inputs were fine but outputs had irregular signals:
So I opted for replacing this custom (taking a good one from a dead Vigilante board) :
This was the right move since sprites were correcly restored:
End of job.