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Dogyuun repair log #2

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Mar 212018

Got from Portugal another Dogyuun PCB (after the one of some months ago), this was declared as ‘dead’ by the owner :

And it was so.All I got was a steady black screen, no activity on board, no clock on 68000 main CPU.I checked voltages on edge connector and there was no +5V so the board was actually not powered :

A quick inspection revealed corrosion on edge connector:

Once cleaned it the board booted and played fine but sound samples were muffled and some static noise was present :

Some sign of electrolytic capacitor leaking was present on sound section :

I fired up my ESR meter and started measuring capacitors.A couple of them, the 220uF 16V @C7 and the 10uF 16V @C9, gave no reading so out of range of my meter (0-99 Ohm)

I replaced them, this restored clear sound.No other issue were found so board 100% fixed.

Recreating the Commodore 16 PLA

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Mar 132018

I recently picked up a nice boxed Commodore 16 for not too bad a price.
The PLA found in this is a MOS variant of the PLS100 PLA chip. I don’t believe it can natively be dumped as it seems to have its connection on pin 1 severed internally and decapping done some time ago revealed it was neither a PLS100 or 82S100 device either despite the pinout being the same.

I wanted to make a replacement using the NOS PLS100 chips I have because some people like that sort of thing and there doesn’t seem to be anything out there publically already.

I hooked up the PLA to an Arduino MEGA and wrote a small program to count through all combinations of the address pins and log the outputs to a 64KB binary file.
From here I wrote a program that converted the file to a truth table

and finally into equations which I could compile to a PLS100 fusemap using the old easyABEL program.

From here I could program a blank PLS100 and test in a real machine.

Still need to do some testing but early signs are looking good.

Backing up an old BBC Micro cassette tape

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Feb 252018

My friend was wanting to backup an old BBC Micro cassette tape that he believed had a game on it his grandad had made. The tape was marked up as “The Wizards Mountain”

I’d never backed up a cassette tape before and I didn’t even own a tape player anymore.
I originally tried buying a really cheap and nasty portable tape player

This was a total disaster and I kept getting inconsistent reads on various parts but between several reads I had what looked like a complete good read.
Using the ‘BBCTAPEDISC’ program I was able read the data directly from the ‘line-in’ source and it also gave a live update on each block recovered so I could see what was failing.

I originally tried stitching different parts together to make a good file but I just couldn’t get it to work properly so I asked around to see if I could borrow a better tape player. Fairly quickly I ended up with this

This gave me an almost perfect read first time. I ended up with a disc image instead of a tape image but thats fine with me as it loads faster.
The outcome is a text adventure game that appears to have been made with GAC.

Its actually a nice story which I still need to finish once I get some time but we are both really happy to have this saved.

Silent Scope Fortune Hunter DS2430 replacements

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Jan 272018

I now have a way of creating new DS2430 replacements for a Konami Viper Silent Scope Fortune Hunter game.
I can only do Silent Scope FH at the moment but I might expand to other titles in the future if I get hold of the hardware.
The DS2430 has a unique factory lasered registration number which is used as part of the security of these things. As long as there is a good Timekeeper NVRAM fitted then the game will reinitialise it on this game and it does not seem to play a part in the security.

If anyone needs a replacement then get in touch and we can sort something out. I will need the ROM ID from a new DS2430 in order to make a new file.

Reader submitted posts

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Jan 012018

Over the years there have been people asking if they can submit posts of their own.
Aside from friends of mine I have never really wanted to open up registrations for everyone.
I have now finally got around to enabling a frontend to allow people to submit their own posts.
It can be found under the “Contact/Links” menu and is just a trial right now.
If it doesn’t take off or gets abused in any way then it will be removed and we will go back to business as usual.
Hopefully we will get some more diverse content going on as a result of this

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