Got another Pacmania faulty.
This time the sprites were glitchy with some black lines
Custom 39 is usually involved in sprites generation but after testing with a good one problem remained.
There are two 74ls377 connected to it and one @A3 has one missing output.
Changing it fixed the board
Received this board from a friend which booted to a static screen
Decided to have a look immediately to the 2k work ram which was a Toshiba which is normally prone to faults.
Changed with an Hitachi 2k
And game 100% fixed with no other errors
Another custom IC successfully reproduced, it’s the Irem ‘KNA6032701’ , a 42 pin DIP 600mil IC used on M62 (Kung-Fu Master, Lode Runner, Spelunker and other), M75 (Vigilante) and M72 (on some type of ‘M72-B-D board) hardware
As usual I reproduced it my way by observing how it was reverse-engineered on bootleg boards obtaining in a board layout with pretty same dimensions of original part :
Testing on a Kung-Fu Master PCB :
Received for repair from New Zealand this The New Zealand Story PCB (sorry for the wordplay…), the one layer hardware revision :
Board booted up but graphics were totally wrong :
GFX data are stored in eight 28 pin 1Mbit MASK ROMs whose pinout is pretty identical to 32 pin 1Mbit non-JEDEC EPROM (extra pins apart)
Before dumping them I used my logic probe and found stuck upper address lines (pin 12-13-14-15)
I traced the address lines back to outputs of a 74LS174 @U9 whose inputs were floating, these came from a Fujitsu 74LS374 @U41:
Inputs of it were toggling but all outputs were stuck at undefined voltage level of 1.48V, this is the typical way of failure of Fujitsu TTLs :
The chip failed the out-of-circuit testing, all outputs were indeed in ‘Z’ (or high-impedance if you prefer) state :
Once replaced the IC the graphics were restored but I noticed some corruption on title screen :
I dumped the 1Mbit MASK ROMs and my programmer complained about the one @U7 :
This was a good chance to use one of my adapters I designed some time ago for replacing the 28 pin 1Mbit MASK ROMs with a TSSOP Flash ROM
But suddenly during power cycling the graphics went bad again :
I quickly pinpointed the fault to another 74LS374 @U10 with floating outputs, another Fujitsu one obviously :
Chip totally failed the out-of-circuit testing:
Graphics were now perfect so I started a game but controls didn’t work, the main character of both players moved by itself:
Looking at hardware I figured out the I/O circuit.The inputs from JAMMA connector go to some custom resistor arrays marked ‘X2-005’ and then signals are routed to a 52 pin SDIP custom chip marked ‘X1-004’ that handles them :
Resistor arrays did their job by pulling-up the signals and then routing them to the custom so most likely the ‘X1-004’ was bad.I played the card of replacing it but I had to struggle before finding a good spare as it seems this custom is quite prone to failure.I tried two donor parts but they were faulty until I caught the good one:
This fixed the controls and board completely.Repair accomplished.
The site has now been switched to use SSL. Hopefully this works for others and not just myself.
Thanks