JAMMArcade.net – Page 43

Namco ‘CUS130’ reproduction

Reproductions Comments Off

May 112018

Some years ago I came across to a Rolling Thunder PCB where the custom marked ‘130’ was replaced by a small sub-board (don’t know if made from Namco or bootlegers, from manufacturing I presume the latter)

It seems the original custom is used only on Rolling Thunder PCB where, indeed, you can find it marked as ‘130’ in form of a DIP40 IC:

Whereas on schematics it’s shown as ’41’ like in Metrocross and Baraduke PCBs but it’s not the same and changes from game to game (the custom is basically an address decoder for generating the memory map which, indeed, is specific to a certain game)

After some time I sold the board but before doing this I took a couple of high-res scans of parts and solder side of this replacement PCB with the intention to reproduce it someday in a modern way.That’s what I successfully made recently :

I hope this will help to repair our Rolling Thunder PCBs with a faulty ‘CUS130’ as it seems it’s a quite prone to failure part.

Bucky O’ Hare repair log #3

PCB Repair Logs 1 Response »

May 092018

Received from Portugal this Bucky O’ Hare PCB for repair:

Board was failing the POST all the time showing a ‘SOUND SYSTEM BAD’ message

The sound system was previoulsy reworked : the YM2151 was socketed

and the ‘054986A’ audio module had electrolytic capacitors replaced with thru-hole ones:

The solder side of the module showed signs of repairs too :

I suspected a broken trace underneath the module so I replaced it with a good one taken from a parts board.The error on POST changed to this :

I looked at the board and found that actually the device @C4 is the custom ‘054539’ while the one @C5 is 32k x 8-bit SRAM (whose data/address bus is connected to the custom)

Probing the RAM revealed that data lines were all stuck high:

Piggybacking it had no effect so most likely the ‘054539’ ASIC was bad.I removed it:

Soldered back a spare :

Board booted up fine and entered in game with no further issues.Another repair accomplished.

Midnight Resistance repair log

PCB Repair Logs Comments Off

May 082018

I got this Data East – Midnight Resistance pcb from a friend.

He said that he dropped a ground wire onto the pcb by mistake and he thought it touched the pins on one of the L7B0072 custom ICs.

I booted the pcb and the game was running blind. Sounds and inputs was working fine, but a complete black image on the screen.

Been working on this hardware before, I knew that the palette RAM was located at J21 and J22, so I started checking their datalines with the scope

Hmm, zero activity

I then piggybacked a pair of new RAMs (6116 type) on top of the original RAMs

Voila, graphics are back 🙂

I then promptly desoldered the RAMs

and soldered a pair of sockets in their place. And the new RAMs

Job done 🙂

Wonder Boy repair log #2

PCB Repair Logs Comments Off

May 072018

Received from USA this Wonder Boy PCB for repair, actually the board was a factory conversion on Sega System 1A hardware:

When powered it up I got most of times a steady black screen, rarely an ‘ERROR ROM 4’ message:

I fired up my Fluke 9010A to perform a ROM test.On some devices sometimes a valid signature was returned but more often I got error and a different signature :

There are six program ROMs:

When I dumped them my programmer complained about some bad contact:

It turned out legs of some EPROMs were dirty and oxidized.After polished them the board booted up but clearly a color was missing (the RED one) and GFX faults were present :

Doing a visual inspection I found a couple of broken 1K bussed resistor networks :

After checked connections I figured out they were used as resistor ladder in the palette circuit.I replaced them, this restored the three RGB colors and showed better the grahics faults:

Backgrounds had wrong colors and some sprites (like main character) had missing parts and vertical lines through.As for first issue I went back to the color circuit where @IC151 lies a TMM2016 (8K x 8-bit) static RAM (whose data bits are routed to some 74LS175 flip-flop and finally converted to analog by the above mentioned resistor ladders)

Probing it revealed a unhealthy signal on an address line (A10 , pin 19), here’s a comparison with a good signal on the left:

Sure enough I removed the RAM :

Device failed the out-of-circuit testing:

Now the sprites issue.Relevant data is stored in four 27128 EPROMs installed on a small piggyback board:

Devices were dumped as good.After a quick check with my multimeter I found a missing connection between a data line of a ROM and the header which goes into the sockets :

I restored the connection and this fixed board completely.Another repair accomplished.

Michael Jackson’s MoonWalker repair log #3

PCB Repair Logs Comments Off

May 052018

Received from UK this Michael Jackson’s MoonWalker PCB (Sega System 18 hardware)

Board gave a steady black screen on power up, no sign of activity on main CPU busses.I transfered on a same board of mine the FD1094 module along with the 8751 MCU and they worked fine.I used my ROM board but still no boot so I came to the conclusion that fault was located on motherboard.Looking for WORK RAMs and I found them :

Two Toshiba TC5563 (8K x 8-bit static RAMs) which means high unreliability and chance of failure.I piggybacked a good chip on the one @IC5 and board booted into game: