PCB Repair Logs – Page 64

Raiden Repair Log

Jun 012016

Initial Symptoms

Static junk on screen, which changes between reboots.
No sound or evidence that game is running in background.

Sony PVM monitor wouldn’t sync in RGB mode, but would (for some reason) in Y/R-Y/B-Y mode.

Random junk when powered. (purple image is due to monitor problem)

CPU Boot Problem

Probing CPU interrupts showed that sometimes V-Blank interrupts were active, sometimes not. Initial check of EPROMs showed that one was dead, but replacing did not solve the problem. Probing with a logic analyser showed that the data/address bus of the main CPU was pulsing, and the game wasn’t watchdogging so deeper investigation was required.

Tracing with a Saleae logic-8 showed that the first v-sync interrupt was getting acknowledged by the CPU, but subsequent interrupts were ignored. Digging futher I generated a partially complete address/data trace by the (shared) data+address bus and the bus status lines (BS0-2). Since my analyser is only 8-bits, I could only trace 5 data+address lines at once. I wrote a script to combine multiple traces using the bus status lines to synchronise the data. Luckily the behaviour was deterministic, and I could extract enough trace data (12-bits of both data and address) to work out a full trace by correlating the data with a mapped ROM dump from Mame. Doing this I found that one of the RAMs was faulty; The stack was getting corrupted, causing a ret instruction to jump to an unexpected program address. Swapping the program RAM resulted in the game booting.

Bad SRAM of main CPU. Socketed and replaced.

New Symptoms:

Some tiles have flickering horizontal bars
Some tiles seem to not change from top to bottom (in horizonal screen)
Sound crackly and missing music

Background tiles are corrupted

Tile Corruption Problem

Probing the tile ROMs shows that ROM U105 address lines 1-4 were floating. These were driven by the SEI0020BU custom chip at U102. Pulling the SEI0020BU and swapping it with it’s neighbour switched the tile corruption. Clearly the SEI0020BU was the cause of the problem. Annoyingly these aren’t easy to come by.

Reverse Engineering the SEI0020BU

I guessed that the main function of the SEI0020BU was to drive the addresses of the ROM chip in the direction of the raster. I checked the connections of the SEI0020BU with a multimeter and worked out the function of each pin (see schematic below for more details).

Checking the Mame source confirmed that the address mapping for this chip corresponded with the x-axis scroll register. I guessed the purpose of the chip was to store an x-axis scroll offset and add that result to the raster x-position. I guessed that only 8 bits of shift were actually needed, and I knocked up a prototype on a breadboard, which seemed to work well.

SEI0020BU breadboard prototype

With a working prototype, I got to work using CadSoft EAGLE (PCB CAD tool) to design a PCB daughterboard for a more permanent solution. The PCB was printed by Seeed, and delivered in a few weeks.

First SEI0020BU daughter board

Once the printed PCBs were delivered, they seemd to work well, but I’d made a few mistakes. Firstly, the output from the LS156 should have been pulled high. Secondly, only 8 bits for the shift offset was insufficient – I actually needed 9 bits. This was a stupid mistake – I’d been unable to test the full shift range properly on my test rig because of a faulty joystick adaptor! Once I tested the board in a cabinet, it was clear that scrolling too far to the left (offset register wraps) causes the tiles to distort (-1 wrapped to 255 instead of 511).

I managed to hack a fix onto the PCB by piggy backing an extra 8-bit buffer and a 4-bit adder onto the PCB, cutting a trace and wiring up with patch wires. The modified PCB finally worked properly, and the graphics were fixed. I wasn’t happy with it though – I’d printed a PCB, so I thought I may as well finish the job!

Patched SEI0020BU replacement daughterboard

I modified my design in Eagle (see schematic below), and ordered a new set of PCBs to be printed.

Schematic for Raiden SEI0020BU replacement

The new PCBs arrived, and worked perfectly – phew!

Final working SEI0020BU replacement daughterboard

Sound Fix

Sound was working, but distorted and noisy. Probing the sound input to the amplifier with an oscillioscope showed that the signal was weak. This was driven by the HB-41 SIL package. The inputs to the HB-41 looked clean, so it looked like it was bad.

Faulty HB-41 SIL package

Luckily I had a spare on a Seibu Soccer donor board. Hooking it up solved the sound problem. Job done!

Image is clean, and game now functions correctly. Colour correct in arcade cabinet.

Splatterhouse repair log #4

PCB Repair Logs Comments Off

May 262016

I got from New Zealand this genuine Splatterhouse PCB for a repair:

Splatterhouse_PCB

Upon boot the board was stuck on a “ROM TEST START !! PLEASE WAIT…” message displayed upside down :

issue

From my past experience I know for sure this issue is caused by a bad ’64A1′ custom replaceable with a programmed Hitachi HD63701 MCU (plus a patched ‘VOICE0′ ROM in order to handle two custom opcodes of the ’64A1’) following this procedure:

Namco System 1 custom ’64A1′ replacement

But in this case, as you can see from the above picture of the board, the owner already replaced the ’64A1′ (and at same time patched the ‘VOICE0′ ROMs using an hacked 1Mbit JEDEC EPROM in place of a non-JEDEC one ) and this didn’t fix the issue.For first I reverted the modification the and reinstalled the original custom ’64A1’.With this configuration the board successfully booted into game although some sound samples were bad.This lead me to think that there could be some problem is the data bus of the VOICE ROMs which prevented the HD63701 MCU to correctly read the patched data causing the missing boot. :

VOICE_ROMS

So, assisted by schematics, I went to check the involved circuit and found that pin 20 (data line D6) of the VOICE ROMs (Splatterhouse use only four of them to store samples) was not daisy-chained as it should have been:

VOICE_ROM_DATA_BUS

In the above snippet of schematics you can see (red mark) where extactly trace was interrupted.I simply used a bit of AWG30 wire to restore comnection:

patched_PIN20_VOICE_ROMS

This fixed completely the game using both the original ’64A1′ custom and the HD63701 MCU.End of job.

Psychic 5 repair log #1

PCB Repair Logs, Repair Logs 6 Responses »

May 192016

Last year after a lot of research I succeded to buy at a good price an original board of Psychic 5 , one of my favourite game of all time, which was really in mint conditions.

psychic5

Some days ago I picked it up for a play and after some minutes the game developed this problem during attract mode:

psy5

psy3

psy2

After some more time the game was total yellowish:

psy4

Game hasn’t any schematics available and there are not any games known to me which have similar hardware and schematics available.

I could only go blind and try to find the reason of the fault.

So I started to short some signals of srams looking for palette changings and I found a couple of them at pos.6N and 6M, 16kbits.

The one at pos.6N had the first 4 data pins low and I was pretty sure either it was faulty or the 74ls245 connected to the data bits.

After desoldering, the sram 2018 was tested good in the programmer. That meant that the programmers didn’t use all data pins of the palette rams. The 74ls245 was good because it could drive correctly the signals without the ram installed.

I tested some TTLs nearby looking for strange signals but found nothing.

Decided to go brute force using my logic comparator and testing everything on the video board but starting with FUJITSU parts which are known to be very unreliable.

The logic comparator found a 74ls08 with all the outputs faulty

psy6

I double checked the outputs with a logic probe and they were all in the grey area (no good logic signal).

After changing it I fix the problem 100%

psy8

psy1

So FUJITSU brand proves once again to be really unreliable!

Dangun Feveron repair log

PCB Repair Logs Comments Off

May 132016

More than a repair a quick fix.

I got this Dangun Feveron PCB :

Dangun_Feveron_PCB

The owner said that most of sprites were scrambled and I could confirm the issue upon powered up the board:

Sprites data are stored into two 42 pin 32Mbit MASK ROMs @U25-U26:

sprites_ROMs

When I went to probe them I noticed a broken jumper @JP3:

broken_jumper@J3

Checking with a multimeter the connections of this jumper relevealed that point ‘2’ was connected to pin 32 of the two MASKs ROMs, therefore the higher address line A20.So, signal coming from point ‘3’ was not reaching this pin due this broken jumper and this caused the sprites issue.Once restored it:

RSCN2919

all came back to normality.End of job.

Batsugun Special Ver. repair log

General, PCB Repair Logs 1 Response »

May 122016

Received this Batsugun Special Ver. PCB for a repair:

Batsugun_Special_ver_Japan_PCB

Game played fine but colors were all dull and washed-out, take a look at this comparison with a MAME snapshot on the left:

colors_comparison

or this video:

This was a clear sign of some troubles in colors palette circuitry.After studying the hardware, I was able to locate this section by shortcircuting some address/data lines of two CXK5816 SRAMs @U39 and U40 and at the same time observing color changes on screen:

palette_circutry

Besides the two mentioned SRAMs, you can see some 74LS245 and two 74HC273 involved in data bus (the first ones in exchanging data from/to the two RAMs, the latter in latching).When I went to probe the two 74HC273 I found that input pin 13 of the one @U43 was stuck low and its corresponding output pin 12 showed only weak signals:

74HC274@U43_probing