Today I dumped the PAL from an original Juno First PCB.PAL is at location B6 of lower board, part name is scratched off but schematics reports it as a PAL10L8.Dump has been tested as working in a GAL16V8 targeting device.
Today we have some new PAL dumps from the following boards:
All dumps have been tested and working in GAL targeting devices.
I got this Truxton PCB (export version of Tatsujin) in a recent operator raid:
Once powered it up board showed GFX issue, the sprites were blocky :
Besides, there was some kind of video interference, this is a common issue on this board and usually it’s due capacitors in the audio section, indeed I found a 470uF 16V one with bad capacitance :
Back to the sprites issue, relevant data are stored in four 1Mbit 28 pin MASK ROMs :
I went to dump them and found a faulty one:
Replacing it with one from a donor board didn’t fix the issue therefore I went on in my troubleshooting.Each data bit of the sprites MASK ROMs is fed into inputs of four 8-bit 74LS166 register.I probed them with my logic comparator and led on output pin 13 lit for two of them:
I desoldered the ICs:
They both failed the out-out-circuit testing (obviously they were from Fujitsu) :
Sprites were fully restored :
The last issue I had to fix was that Player 1 Start input didn’t work.The inputs circuitry was previously reworked by someone (note the replaced 74LS240 and some patched traces)
I traced Player 1 Start back from pin 17 parts side of JAMMA connector to an end of a 220 Ohm resistor @R17 whose other end was tied to pin 13 of the 74SL240 @21K :
Signal on pin 17 of the JAMMA connector and on first end of the resistor was high and correctly toggling when pressing the button while was totally missing on pin 13 of the 74LS240.Therefore the only culprit had to be the resistor.Indeed I got no reading measuring it on circuit:
I removed and tested the resistor out-of-circuit having confirm it was opened:
Job done.
Yes, yet another Double Dragon PCB on the bench.
The board was in good shape:
but it didn’t pass the self-test sitting on a ‘63701 ERROR:
The /HALT line of the HD63701 MCU was asserted, this was sign of some trouble in its busses.I swapped a good chip with no change so I went to look at schematics.All was good until I found no continuity between the address line ‘A0’ (pin 50) of the MCU with pin 3 of the 74F157 @IC8:
Tracing back the address line I could figure out where connection was interrupted, exactly under the 74F157 @IC7 so I removed it.Inspecting the involved area with a USB microscope revealed a corroded trace :
I patched it with some AWG30 wire:
With this fix finally the board passed the self-test but two issues were present in game : sound was missing and backgrounds had jailbars :
The first issue was due a missing 10Kohm potentiometer in the sound section:
The backgrounds GFX data are stored into four 27512 OTP devices on video board :
When I went to dump the ones @IC108 ans IC109 my programmer warned me about a bad contact on pin 19 (data line ‘D7’) of both :
Obviously the resulting dumps didn’t match the ones from MAME ROM sets so I programmed two 27C512 EPROMs as replacement.This restored graphics completely.Yes, yet another Double Dragon PCB fixed!
I dumped a PLD from a working Van-Van Car PCB (manufactured by Sanritsu or Karateco).Device was a unprotected PAL16L2 labeled ‘VAN-83’ @IC79, there are other three PALs on PCB but they are registered and secured.Dump is tested as working in a GAL16V8 targeting device.