Today I dumped the PALs from a bootleg of Terra Force.Original devices were two unsecured PAL16R4 whose dumps I successfully converted (using PALtoGAL utility) and tested into GAL16V8 targeting devices
Not a real repair but just a quick “dirty” fix for this Konami Teenage Mutant Hero Turtles PCB :
All was fine but the music played at the start of a game (when turtles jump from palace) was missing :
A usual I started my troubleshooting with a visual inspection and I found soon the culprit.One of the two 640KHz ceramic resonator was missing:
I took it from a dead donor board :
and once fitted the missing music was restored.End of (small…) job.
I had a spare Sega System16B ROM board type ‘171-5797’.Originally it mounted the E-Swat ROM set but I decided to convert to Golden Axe since I missed this game in my collection :
Atter burning the Golden Axe MAME rom set, I powered the board up and game was fully playable but with a noticeable sprites issue:
Judging from fault, I immediately thought about an addressing trouble of the sprite EPROMs (27C020 devices) so I went to check for continuity of their address lines.They were properly daisy-chained each other but the pin 30 (A17) of all of them was not connected to any pin of the ‘CN2’ interconnect (signal to address lines come from motherboard) :
Lack of signal on this A17 address line was confirmed also by my analog scope (good signal on left, bad on right of the picture below):
So, the trace had to be broken under the ‘CN2’ interconnect.Being not available schematics and wanting to avoid to desolder the whole connector, I soldered the end of a wire to PIN 30 of a sprite EPROM and with the other end I touched each pin of the ‘CN2’ interconnect that gave me no continuity until I hit the right one restoring correct sprites:
Lastly, I made the fix permament holding the wire with some hot glue:
That’s all for today.
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.
