Some time ago ‘Layer’ asked me about a PAL dump from a Twin Eagle II PCB since his board was missing the chip and could not boot.Today I’ve dumped this PAL from a dead board hoping he can test the dump (on a GAL16V8 targerting device) and fix his board.
********UPDATE********
‘Layer’ successfully tested the PAL dump and at same time revived his board.Thanks to him for the feedback.
Got this Frogger PCB from my friend Josef for a repair.Actually it was the Sega/Gremlin version which uses Konami Classic pinout (like Gyruss, Scramble and many others):
PCB played fine but had a strange issue where sound was very quiet on my supergun while was completely silent on a cabinet.All audio circuitry is located on upper board.Looking at i I could notice that someone had previously reworked (replacing it perhaps) the M51516L amplifier ending with break some traces and using some jumper wires to fix it:
Luckily schematics were available so I went to check every connection in this part of circuit.Everything seemed fine until I came across to something odd : PIN 6 (ground) of M51516L amplifier was intentionally jumpered to positive terminal of a 100uF 25V electrolytic capacitor (so both terminals was shorted to ground) :
while schematics showed it connected to collector of a transistor through a 1KOhm resistor :
Removing this jumper wire restored full sound.
I got this Ghox PCB from my friend ‘robotype’ for a repair:
On the power up I was greeted by this static screen:
Address/data bus of 68000 main CPU was inactive.As usual I went to loot at MAME source (that is a bit like a bible for us repairers) and I found this interesting comment:
// Ghox 68K reads data from MCU shared RAM and writes it to main RAM.
I could identify the HD647180 MCU RAM in a 6116 @U14 :
So I went to probe it with my analog oscilloscope and found weak signal on some address lines (good one on left picture, bad on right) :
I piggbacked this RAM and board booted showing this error message:
After replaced the MCU RAM (which actually failed the out-of-circuit test), I traced the palette RAMs in two 6116 chips @U41 and U42 :
One of them had already been replaced so I went to piggyback the other one @U41 and board successfully booted:
Obviously the chip failed miserably the test on my programmer:
End of job.
Today I successfully tested on a Turbo Force PCB the PAL dumps previously done by Porchy and at same time I dumped the missing one @U100.Now we have a complete PAL dump set of this great vertical shoot ’em up released by Video System in 1991.
I got this board from my friend Joachim for a repair.A Nintendo Playchoice-10 system:
For the uninitiated, Playchoice-10 is the arcade hardware developed by Nintendo to run its most popular NES games inside an arcade cabinet.The games for this system are in the modular form of carts which are plugged into one of the ten open slots on the PlayChoice-10’s motherboard:
When I first powered it up, I was greeted by a solid black screen, no activity on main Z80 CPU.A closer inspection revealed a missing 8MHz crystal @X1 which supplies the clock to main CPU:
Once fitted a new crystal I had clock signal on pin 6 of the Z80 but the watchdog circuti was active ( /RESET line was constantly going to HIGH to LOW state in a endess loop).I pulled the Z80 and tried it in a good board having confirm it was faulty.With a good CPU all I got was a green screen:
While probing chips I came across a TMM2115 (6116 compatible) RAM @4K which was burning hot to the touch, I remove it and my programmer reported it as shorted:
With a good RAM I got always that green screen but could hear sound sign that the board was playing ‘blind’.This was a good chance to use my Fluke 9010A troubleshooter.MAME reported this memory map:
0000 – 3fff = Program ROM (8T)
8000 – 87ff = RAM (8V)
8800 – 8fff = RAM (8W)
9000 – 97ff = SRAM (8R – Videoram)
I could successully perform a RAM LONG test on address space of RAM @8V and 8W but I got an error on the videoram @8R (all these RAMs were 6116 compatible):
Once removed, the chip failed the out-of-circuit test:
Finally I got it running:
but, since the motherboard (PCH1-01-CPU) was a dual monitor type, I could not display the playfield (although it came with this JAMMA adapter which provides also outputs for a second arcade or VGA monitor)
