Sunday, 17 November 2019

Raiden repair log

Received some time ago from Portugal this faulty Raiden PCB for repair (actually the hardware revision with Altera EPLDs) 


A said, the board was not properly working since on power up it was stuck on a static screen on which you could insert coin but nothing more :

 

Main (and SUB) CPU is a NEC V30 (real part name uPD70116) 

Probing it revealed that HALT pin (active HIGH) was asserted hence the CPU stopped its processing putting its busses into a high-impedance (or tri-state if you want) state :

The main CPU uses four 8k x 8-bit static RAMs:

 
Probing them with a scope revealed weak signals on data lines of the ones @U028 and U021, here's a comparison with an healtly signal on the left of the below picture :


This and the fact that RAM chips were Toshiba TMM2063 (so very prone to failure) lead me to remove them :


Both chips faied the out-of-circuit testing :


Installed sockets and fresh RAMs :


I powered board up and it booted into game with no further issues.Repair accomplished.




Sunday, 3 November 2019

Golden Axe: The Revenge of Death Adder repair log

Received some time ago from USA a Golden Axe: The Revenge of Death Adder PCB for repair (a beat'em up released in 1992 by Sega on System 32 hardware)


Game played absolutely fine but sound was totally absent.Putting fingers on solder side of amplifier resulted in a buzzing noise hence analog sound circuit was doing its job and nature of fault was digital :

 

I went into TEST MODE and run a ROM/RAM check which reported a bad device @IC16 :


The device is a 8k x 8-bit static RAM which is part of the digital audio circuit ruled by a Z80 CPU, this perfectly explained the lack of sound :


Obviously the first thing I did was to remove the chip and test it out-of-circuit but it turned out to be good so I socketed and reinstalled it.Probing the the three control lines (/CE, /OE, /WE) with a scope revelaled static signals :



I traced them back to a custom ASIC @IC38 marked '315-5385' (in QFP128 package), a quick search on the net told me it's was the system controller/timer :


Having a faulty motherboard I decided to try the swap.The chip came off quite easily with hot air :

 The spare was installed and all pins checked under a microscope for possible bridges :


I powered the board up again and sound was fully restored.Another repair accomplished.


Tuesday, 29 October 2019

Image Fight repair log

Received from Japan an Image Fight PCB for repair (game is a vertical shooter  developed and published by Irem on M72 hardware)


On power up the board seemed to properly boot, something moved on screen but then got stuck on garbage :



As many of  you may know, this is a three stack set hence, having a good R-Type boardset, I started to swap boards.I was able to narrow the fault in the bottom PCB :

First of all I probed these four 8k x 8-bit static RAMs @IC34-IC35-IC36-IC37 :


I found that their WRITE ENABLE input (pin 27) was stuck high, no activity/pulsing like observed on my good R-Type :


Tracing the signals back I could not find anything abnormal until I came across a 74LS32 @IC51 :



 The logic analyzer showed no LOW pulsing on output pin 11 when inputs 12 and 13 got asserted :


I piggybacked the device and board booted into game although background graphics were corrupted :

 

I removed the TTL device and it failed the out-of-circuit testing :


Time to install some machined round socket and a good IC :


The next power up gave me a fully working game with no other issue.Repair accomplished.



Thursday, 24 October 2019

1943 Kai - Midway Kaisen repair log

Received from Austria for a 1943 Kai - Midway Kaisen PCB for repair (the game is an update of 1943 with tweaked weapons, fewer levels, and a new soundtrack released in Japan only).Set was in good shape in both CPU and VIDEO board :



Game was playable but with severe sprites issue :

 

Objects are generated on bottom video board by a custom IC (in PLCC84 package) marked '86S105'


This is another well known unreliable and prone to failure part (which really would need to be reproduced someday) which I had to replace many times hence I was pretty sure it was bad also on this board.I didn't have any spare but the owner of the board came to help and sent me a working one taken from a Pang PCB.The part arrived some days later :


Time to remove the old one and install the spare :


This lead to a great improvement, sprites looked much better but yet not perfect as they were still slightly glitched with vertical lines through them:


Schematics show that on VIDEO board there are two identical sprite line buffer circuits where two 2K x 8-bit static RAMs lie :


On my board they were replaced :


During removal of the RAMs some traces on solder side were broken and then repaired with some wire .


I probed the two RAMs and found that pin 16 (data line D6) of the one @7D was stuck HIGH :


According to schematics this pin should be tied to pin 17 of the 74LS273 @6E and pin 9 of the 74LS257 @5D :


I checked on the board and found that connection to pin 9 of the 74LS257 @7D was missing.I promptly run a jumper wire between the two points:


This made the trick and fixed board completely.Another successful repair.


Tuesday, 22 October 2019

Pac-Land repair log

Got for repair this original Pac-Land PCB (manufactured by Namco and licensed to SIPEM) :


The board was in very good shape but it booted all the time to a static screen :


Probing the program ROMs revealed the /CE line of two devices were stuck HIGH or silent :


The signals come from a 74LS139 @7D :


Being a Fujitsu TTL I was aware of the way they usually fail so I didn't spend much time on it.I removed the device, it miserably failed the out-of-circuit testing :


Replacing it allowed the board to boot, game was fully playable but backgound graphics were all blocky :


The issue was obviously located in the tilemap generation and, judging from kind of fault, more precisely in the addressing circuit.Schematics show there are a couple of 74LS86 @9J and 10P that generate some addresses to the backgrounds ROMs :

Devices were again from Fujitsu, they gave troubles when tested in circuit with my HP10529A logic comparator :



They both failed the out-of-circuit testing :




I replaced the two TTLs and powered the board up again sure enough it was fixed and fully working but playing a game I noticed sprites were glitched :



The sprites circuit consists in a couple of custom ICs ('CUS11' and 'CUS12'), four EPROM devices and some logics where I spotted another Fujitsu TTL, a 74LS377 @7K :







The scope showed output pin 9 was floating despite an active input :



Device failed the out-of-circuit testing in that exact gate (pin 9 was, indeed, in 'Z' or high-impedance state)




The replacement finally cured the board.Repair accomplished.




Friday, 18 October 2019

Konami '504' reproduction

This is my own reproduction of the Konami ‘504’ custom IC with the use of simple logic gates and no CPLD or other moderm programmable logics (call it 'poor man's' if you want...).Original part is a 28 pin 600mil IC found on some Konami  PCBs of 80’s , you can refer to this useful spreadsheet (credits to ‘mattosborn’ on KLOV forums) :

 Konami custom ICs


How often this manufacturer has accustomed us, the IC comes with scratched-off part name:


This time I have been facilitated in my work because Konami itself sometimes replaced their custom ICs with daughter-boards which are faithful TTL implementation of the functions.I was able to get the one made for the '504' : 


Then it was only matter to take schematics of this daughter-board and route them to a PCB layout.The final result is a little board with more or less same dimensions of original part (note the simultaneous use of SOIC and TSSOP devices)


 Reproduction was succefully tested on a Track & Field PCB :