Caius

Lightning Fighters repair log #1

Jul 292014

Received today from Spain this Lightning Fighters orginal Konami PCB (bought on Ebay some days ago):

Seller sold this as faulty saying game suffered from graphics glitches.

He was right (positive feedback for his honesty…)

I immediately thought it was something related to tilemap generation since part of screen was doubled and drawn in wrong place while sprites were good.So, I started to check this part of circuit.This hardware, like many other from Konami, use some ASICs in QFP package to generate parts of graphics.This PCB uses two of them to create the tilemaps, they are marked ‘052109’ and ‘051962’ and always used in pair.Checking them I found a couple of lifted pins on the one marked ‘052109’, I reflowed them but issue was still present.

So I started to think about : technically speaking, an ASIC behaviours like a CPU, so in this case it takes datas from graphics ROMs and stores them in RAMs.When it wants to read these stored datas, it addresses the RAMs.

So my issue should have been due a bad RAM adressing since screen fullfilled of zeros, graphics drawn in wrong place are clear symptoms of it.So, I started to check the two 6264 SRAM @H24 and J24.All address lines was shared between except for A2 (pin 8).This abnormality was also confirmed by schematics:

I noticed that someone replaced (or desoldered for testing) these two SRAMs previously so probably he managed to cut the track between the two address lines.So I jumpered them with a bit of AWG30 wire and all graphics came back to normality:

What can I add more?End of job!

Konami GT repair log

Jul 232014

A friend of mine sent me this really mint original Konami GT PCB saying it suffered from vertical stripes across most part of screen.

Fired up the board and …he was right 🙂

Initial test said all RAMs were good so the problem was elsewhere.Without any schematics I started my visual inspection as usual.I noticed that the only IC replaced on this mint PCB was a 74LS157 @H13.Since a socket was installed, I removed this IC and all the part of graphics affected by stripes disappeared so I started to think problem was generated after this part of circuit.In particular I traced an output (pin 7) of this 74LS157 to pin 4 (RAS) of some TMM4164 DRAMs (there are 16 of them).Probing these DRAMs with my logic probe revelaed that on four of them pin 2 (DATA IN) was pulsing but the pin 14 (DATA OUT) was stuck high.So I desoldered (they were @G2, G3, H4, H5 position) and test them in my Hi-Lo Systems ALL-07A programmer and the result was this:

They all failed miserably.I was lucky since had some good 4164 DRAMs taken from a scrap PCB in order to repair a Commodore 64 motherboard.Installed them and goodbye stripes for ever!Board 100% fixed.

Varth bootleg PAL dumps added

PAL Updates Comments Off

Jul 232014

This interesting CPS1 bootleg has seven PLDs, five of them are registered so I could dump only the two combinatorial ones.The first is a PALCE20V8H device that was dumped by me and reversed by Porchy in a GAL20V8 targeting device, the other was dumped and reversed by me into a GAL16V8.Both are tested and working.

Toki PAL dumps added

PAL Updates Comments Off

Jul 092014

Today I’ve dumped all the PALs from an original (by TAD Corporation) Toki PCB.All dumps are tested working in a GAL16V8 target device.There are also other two programmable logic devices on this board (two bipolar PROMS) whose dumps I’m gonna to send to MAME team in order to improve emulation of this funny and addictive game.

Bucky O’ Hare and Martial Champion PAL dumps completed

PAL Updates Comments Off

Jun 272014

My colleague Porchy today dumped two PAL chips I sent him some days ago.They were both 24 pin PLD and both were reversed into a GAL22V10 target device.One is from a Bucky O’ Hare, the other from a Martial Champion, both original PCB.The first was tested by me and it’s working, the latter is untested since my board is faulty.Anyway, now we have complete PAL dump set of these two games.

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