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Nemesis (Konami GT conversion) repair log

PCB Repair Logs Comments Off

May 252019

Received from Portugal a faulty Nemesis PCB for repair, actually a conversion from Konami GT on GX400 hardware.Set is made of a CPU board :

And a VIDEO board :

The game was full playbale with sound but the graphics were glitched as there were jail bars all over the screen:

The fault was obviously located on the bottom VIDEO board therefore first of all I ruled out all the custom ICs by swapping them in a good board, they were all OK.Then I focused on a couple of rows of 4164 dynamic RAMs (some were already replaced) :

They are 64K x 1-bit devices, here’s pinout :

On this board they are used as sprite line buffer like schematics show :

I went to probe them with my scope and I found one with an unhealthy signal on data output pin (good signal for comparison on left of below picture) :

It was the chip @5H which I prompty removed and replaced with a good one :

This fixed the issue and board competely.Repair accomplished.

BINman update

General Comments Off

May 212019

Quick update here.

One small bug fix with the byte sum not clearing when reset.
The analysis routine has been updated to check if alternate bytes are stuck high, low or are all the same.

I think that’s all. There may be other things too but its been a while and I’ve forgotten what they might be.
I’ve since started using source control for my projects so will be able to keep better track of things

Data I/O 29A repair log

Equipment Repair Logs Comments Off

May 212019

I’m not dead!
Some time ago I scored a great deal on eBay for a Data I/O 29A setup with a load of modules and manuals.
Pretty much everything worked great apart from the display was really dim.
It doesn’t look too bad in the picture but it looked much worse in real life

Schematics are readily available for the unit so fault finding was fairly quick.
With the display being dim my initial though was a voltage issue and the schematics have conveniently labelled the area up as “FILAMENT SUPPLY GENERATOR”.

Using the scope I could see straight away the CD4049 hex inverter at U14 was not inverting at all.
Simply replacing this fixed the fault

Sega ‘315-5025’ reproduction

Reproductions 2 Responses »

May 202019

Another reproduction of a custom IC successfully carried out.The part in question is the Sega ‘315-5025’, a 300mil DIP18 chip found on System 1/2 boards, Space Harrier and other Sega hardware from 80s :

It’s basically a shift register used for graphics functions being directly connected to data bus of the ROMs as per Choplifter schematics (it’s shown as a 20 pin IC because it’s compatible with the bigger ‘315-5155’ found on System 16A and Out Run boards)

Since nobody made it before I reproduced this custom my way by studying how it was reverse-engineered in bootlegs:

Testing on a Pitfall II PCB:

I hope this will help people to repair their faulty PCBs being understood that this project, like all my other, will not be made public although nowadays it’s a common thought that everything should be shared and free.Nothing in life is free and if you don’t work for it you certainly shouldn’t expect it, nor do you deserve it for free.

‘Konami-1’ reproduction

Reproductions 1 Response »

May 192019

‘Konami-1’, a simple name given to a custom IC used on many Konami PCBs from early 80s, here’s a filtered list from MAME :

The chip itself is a 600mil DIP42 which most of times comes with scratched-off part name:

It’s basically a 6809 CPU with some minor modifications (different pinout and scrambled opcodes), it was the first custom chip ever produced by this manufacturer.

Studying how it was reverse-engineered by bootleggers I made my own reproduction of it :

Here’s testing on a Jail Break and Gyruss (bootleg) PCBs:

Probably a CPLD based version will come later in order to semplify the board layout but I’m quite happy with it as is.

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