PCB Repair Logs – Page 60

Terminator 2 repair log

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Jul 242016

Got this board from Muddymusic.
Board was filthy when I got it and most IC legs were a nice shade of green. I decided to clean this up first.
20160722_194239

After a good clean the board came out OK, not great but definitely much better. I noticed that a socketed RAM chip had one of its legs hanging out the side of its socket.
20160722_194750

Not sure what effect this would have but I reseated it properly before powering it up.
I replaced all of the single wipe sockets on this board as I really don’t like them.
20160723_130630
20160723_115551

Next up was the power up test and I was greeted with a yellow screen which eventually turned mostly red and stayed that way. I could see the game was booting at least.
20160722_194824

From this point I can be sure the palette circuitry was at fault. Looking at the schematics you can see there are 2 x CXK5856 RAM chips responsible for the palette RAM.
t2_palette

In my experience these RAM’s have been the most unreliable so I desoldered both of them straight away and both of them failed spectacularly when tested out of circuit.
I replaced them and fired up the game.
20160723_151652
20160723_151700
20160723_150306

All seems to be working fine now.
Also dumped all the PAL’s from this too and hopefully will be getting them tested soon.

Devil World repair log

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Jul 212016

Got this Devil World PCB as non working. This game is running on a Konami Twin 16 hardware. It is a two layer board with the first one devoted to CPU/sound and the second one to GFX/video. The two faulty/replaced chips were on the video board and are highlighted in red.

devilworld1

Luckily the board was booting and got stuck on the RAM/ROM test screen with ROM #18 reported as bad (chip #1 on the board picture above).

devilworld2

That ROM is part of a 4 ROMs row which contains the GFXs. They are 40 pins Konami chips and looking in MAME I could see that they were 512kb MASK ROMs. I tried dumping it with my programmer but was unable as it found one dead pin. Compatible EPROMs for these are 27C400 so I burned one and replaced it.

The game was now booting but with a color problem on some tiles.

devilworld3 devilworld5

After a deep look at the video board I could find a Fujitsu 74LS153 located at 10H (chip #2 on the board picture above) with floating outputs (while inputs had healthy pulsing signals). I piggybacked it and got everything corrected. I desoldered the faulty one, put a socket and replaced it. Board is now working perfectly.

devilworld4 devilworld6

Out Zone repair log #3

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Jul 182016

Received this Out Zone PCB for a repair:

DSCN3862

Actually board was a factory conversion from a Zero Wing board (hardware revision ‘TP-015’).When I powered it up, I got nothing of screen, neither the black and white wavy lines sign of the system being initialized like it happens in this Toaplan hardware :

Probing the 68000 main CPU releaved it properly received /RESET signal as well as clock was present.As usual I did my check on CPU/RAM/ROM data/address bus and all was fine.But I went to check the clock signal of the Z80 it was stuck high:

Z80_clock_probing

The clock is generated by a 28MHz oscillator then divided by a 74F163 and inverted by a 74LS04 before reaching pin 6 of Z80 with a frequency of 3.5 MHz:

sound_system

On this kind of Toaplan hardware the Z80 commands not only the sound system but also the I/O, this would explain why the whole system didn’t get initalized since the 68000 could not find the Z80 running.Confident I went to remove the 28MHz oscillator :

DSCN3871

Fitted a good one and :

DSCN3872

Board risen from its grave!Mission accomplished.

Hellfire repair log #2

PCB Repair Logs 2 Responses »

Jul 162016

Got this orginal Hellfire PCB (by Toaplan) for a repair:

DSCN3844

After some initial problem due dirty sockets of program ROMs and oxidized JAMMA edge connector which caused missing boots, I was greeted by this scenario:

Sprites were wrong, garbled and stretched all over the screen.This part of graphics is generated by the custom ASIC ‘FCU’ :

FCU_ASIC

I did a reflow of it but this didn’t lead to any improvement.Probing around I found a 6116 SRAM with some data lines stuck low:

DSCN3847

Chip failed once tested out-of-circuit:

6116@2W_failed

But still no big improvements.Testing TTLs with my logic comparator I found a 74ALS169 counter @3N with bad outputs:

DSCN3849

Its output pin 15 was almost shorted to VCC (only 7.9 Ohm measured)

DSCN3850

Once removed, the chip failed miserably :

74ALS169@3N_reworking

Finally the sprites were correctly drawn but blocky :

DSCN3853

I noticed that, if I pressed down the ROM 9 @4E, sprites were 100% restored:

DSCN3856

Removing the EPROM revealed oxidation on socket pins:

RSCN3858

So I replaced it:

DSCN3860

Installing a new socket fixed game completely.

Double Dragon II – The Revenge repair log

PCB Repair Logs 2 Responses »

Jul 122016

Had this original Double Dragon II – The Revenge in my faulty boards pile so I deciced to take a look it hoping to fix it and complete the trilogy in my collection:

DSCN3795

Once powered it up I was greeted by this static garbage screen: DSCN3797

A static screen is a clear sign of some trouble in the main code execution.So, for first, I went to dump the program ROMs and found a bad device which game me different checksum at each reading.Since my ROM set was an undumped japanese one, I was forced to convert my board into the US set which is available.This did not lead to any improvement so further investigation was needed.When I removed the EPROMs, I noticed that the socket @IC63 (the one of the bad EPROM) was oxidized:

DSCN3798

I decided to replace it.When , before installing the new one, I was checking all the connections, I found an eaten trace underneath which should have tied pin 2 of the 74LS138 @IC64 (which generates the /CE signals for program ROMs) to pin 9 of a 74LS273 @IC71:

broken_trace_IC63_

Once restored the connection board finally booted up but with severe sprites issues and corrupted/missing sound FXs:

Probing RAMs on video board I found some data lines stuck low on a TMM2015 @IC83 :

DSCN3816

This was due two broken traces on solderside which I promptly patched:

broken_trace_IC83

This improved a little the issue giving back the missing lines to sprites but they were still wrong and garbled.Looking at MAME source, I could figured out that one of the two Z80 (the one @IC50) on top board is used as sprites CPU which takes data from a 27512 EPROM @IC37 and write/read them on a 6116 SRAM @IC24 :

srpites_CPU_circuitry

Probing this static RAM (actually a Sanyo LC3517BSL compatible with 6116) revealed weak signals on its address bus:

DSCN3819

Once removed the chip, it failed when tested out-of-circuit:

TMM2015@IC24_reworking

With a good RAM chip all the sprites were correctly restored :

sprites_restored

So I moved to troubleshoot the sound FXs issue.Samples are played by an OKI MSM6295 @IC74 with takes data from two 28 pin 1Mbit MASK ROMs @IC39 and IC40:

ADPCM_circuitry

Probing the two MASK ROMs revealed that data came out when requested so the problem had to be in the OKI MSM6295 chip which played them badly.I removed it :

DSCN3831

and put back a good one:

RSCN3833 This restored ADPCM samples.Board 100% fixed and board trilogy complete!

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