JAMMArcade.net – Page 141

Robocop repair log #2

Aug 172015

Got this original Data East Rocobop for cheap:

Board was marked as not working but when I fired it up all was fine except for sound what was completely missing.Swapping boards with another working set I had , I could pinpoint fault in the top CPU board.Analog section was fine so fault was of digital nature.Sound system is made of a main 6502 CPU, a YM3812 and YM2203 sound synthesis chips:

Probing the 6502 CPU I found that it was undergone an hardware interrupt since its NMI line (pin 6) was low.Technically speaking an interrupt is an asynchronous signal generated to CPU from external peripherals indicating an event that needs immediate attention.

This lead me to think that the YM3812 or the YM2203 were bad (the IRQ line – pin 4- of the 6502 is connected to both these devices) so I desoldered them.But I was wrong since they were good.Analyzyng with a logic probe the TMM2015 SRAM @2F connected to the 6502 CPU revealed nothing abnormal but this didn’t convince me so I used my analog oscilloscope and found weak signal on some data lines compared to healthy ones:

I piggybacked the RAM and sound was fully restored.Time to desoder and test the IC out of circuit in where it failed:

Fitted a new RAM and archivied also this board as fixed.

X Multiply repair log #4

Aug 162015

Got this Irem X-Multiply PCB (actually a conversion from an Hammerin’ Harry M81 board) from my friend Josef for a repair:

It showed a graphical issue where some sprites (like enemy shots) were blocky during gameplay and backgrounds missing during attract mode:

Sprites and tiles data are stored respectively in eight 1Mbit EPROMs on video board for a total of sixteen devices.

Original devices were 1Mbit 28 pin MASK ROM:

https://pdf.datasheetarchive.com/datasheetsmain/Datasheets-X2/DSA62700099.pdf

while who made this conversion used ST M27C1000 :

https://pdf.datasheetarchive.com/indexerfiles/Scans-065/DSA2IH00172244.pdf

Video board has some jumpers which must be closed according to the type of adopted devices :

In this case the jumper configuration was set to ‘EP’ so not suitable for 27C1000 but required the use of JEDEC devices like 27C1001 or 27C010 (while the ‘MASK’ setting can work straight only with the original 28 pin 1Mbit MASK ROMs and not with 27C1000 which, although the similar pinout, have some extra pins to deal with, so some modifications are needed)

Reprogramming all the data for sprites and tiles into 27C010 1Mbit JEDEC EPROMs fixed graphics completely.

Namco NB-1 PAL dump added

PAL Updates Comments Off

Aug 152015

Today I dumped a PAL from a Point Blank PCB (Namco NB-1 hardware).There was another one (a PALCE16V8H) but device is set as registered so not dumpable.Dump is untested for now since board is faulty but we mark it as assumed working anyway.

Undercover Cops repair log #1

PCB Repair Logs, Repair Logs Comments Off

Aug 152015

Got two Undercover Cops PCBs (a native and a Alpha Renewal version converted one):

Both had sound issues.

The first one had all music but sound FXs were missing.In this kind of hardware (IREM M92) music is generated by YM2151 sound synthesis chip while audio samples from a “NANAO GA20” ASIC custom chip (QFP 80)

Probing the pins of the latter revealed no activity on its DATA/ADDRESS bus (it addresses and read data from the MASK ROM ‘W42’ on ROM board)

I dumped this device and it matched the MAME ROM set so problem could be elsewhere.Tracing back the connection from GA20 to the MASK ROM I found that some address lines were not in continuity like the other.I could pinpoint the break in interconnect ‘CN3’ which carryes signals from/to the two device:

A simple reflow was enough to restore the full sound.

The second board was totally silent, no audio at all.All the analog audio circuit was fine.I started to test ICs with my HP10529A logic comparator and when I put the clip on a 74LS74 @IC24 on CPU board, suddenly I got sound.So I inspected the solder side of this IC and found some evident dry joints , in particular pin 16 was not soldered on its pad, (probably I restored connection when I put the clip on it):

Also here a quick reflow was enough to fix the board.

Quick ROM ident program

General Comments Off

Aug 152015

I loved the old WinROMident program for its quick usage but unfortunately it hasnt been updated in a long time.
Ive made a new drag and drop program that uses Romcenter .DAT files

It doesn’t yet support zip files, only single files.
As with everything I make it requires .NET (v4.5) installed on your computer and it probably has a load of bugs too.
Its minimal and quick which is exactly what I need.

Can be found in the Downloads/Software section

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