I got this mint The Outfoxies PCB for a repair from my friend Zoran :
For the uninitiated it’s a fighting game released by Namco in 1994 on Namco NB-2 hardware.The board ran well but had some inputs issue regarding the player one.Down input was not responding while left one was intermittent.This was confirmed also by switch test :
Also in this Namco hardware (like the NA-1/NA-2 and NB-1 ones) the inputs signals from JAMMA pass for first through some SMD EMI filters (which suppress high frequency interferences).Using a multimeter revealed that JAMMA pin 19 and 20 parts side had continuity with the inputs of the EMI filter @FL12 but the outputs lost their connection with the pads:
Restablishing the lost connection with a bit of AWG30 wire fixed the issue completely:
I bought this pretty rare Exzisus PCB as faulty from our member Corrado:
For the uninitiated it’s horizontal scrolling shooter arcade game released by Taito Corporation in 1987.There are two PCB version, one not JAMMA with separate RGB outputs for background and sprites, the other with a single video outputs and is JAMMA compliant.The one I got was the latter.
Once powered the board up I immediately noticed two issues : all sprites were horizontal lines shifted and repeated on each half of screen :
and sound was missing at all (although I could hear some noises sign that amplifier was good).Studying a bit the hardware, I could figure out how sprites were drawed.The four sprite EPROMS are addressed by a custom, marked ‘TC0010VC’ (there is another one for the backgrounds) while the data were written on two 6116 RAMs which were addressed by the same custom but not directly but through two 74LS273 latches and four 74ALS169 counters:
Probing the latter with my logic comparator I got troubles on the outputs of three of them so, although false readings are quite common for this kind of device I decided to remove them.Tested in my BK560A they all failed:
Once replaced these counters, the sprites were correctly restored:
So I could focus on the sound lack.Connecting an external amplifier to the analog output of the YM3012 DAC I could hear all the sound as well as on the input of the near TL074CN OP-AMP but nothing on its output :
This was confimed also on my analog scope (good input on the left, no output on the right):
Fitted a new TL074CN @J21 restored full sound.End of job.
I bought this faulty Point Blank PCB for cheap on Ebay:
Seller said it had graphical corruption and was missing a primary color and sound.When I powered it up I actually had sound but the other two issues were there:
The missing color was the green, tracing the pin 12 solderside back from JAMMA connector I found the culprit : one of the three SMD transistor ( each of which drives a color output) was missing:
Green was so restored :
but graphical troubles were still there.Inspecting the board I found that some pins of the custom C355 were smashed:
This custom handles the motion objects (sprites) and my issue concerned this part of graphics.Having a spare Namco NB-1 board I opted for a replacement of this ASIC :
After some work and pads rebuilding, I ended up with this result:
In this way graphics were completely restored but sprites had jailbairs:
Pressing down the board fixed the issue temporarily, inspecting again the board revealed a liften pin on a TC51832 (62256 compatible)RAM @12R:
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:
