30 Aug 2018

Neo Geo AES/MVS battery free 16 in 1 memory card - part 2

I had the most difficulties finding good FRAMs chips... Most of them are just fake/faulty, maybe that's why no one makes those memcards anymore.
 
Anyway after soldering a good FRAM chip, everything worked as expected (don't look at the PCMCIA connector, it's a scavenged part I pulled from old computer stuff, not in best condition but good enough for testing):
  



23 Aug 2018

Lynx II - Atari (repair log)

This Lynx II was left to me in a deal with the hope I could have a look. Owner said he had done the +5V mod then reversed it and console then didn't power up. He also mentioned before the mod the screen wasn't working.


First, all parts that had been removed for the +5V mod were back in place and correctly oriented. I probed the transistors, diodes and resistors involved in the power supply part and found a 10kΩ resistor (R73) that was broken and read infinitum. Unfortunately I didn't have any SMD resistor with the correct value in my stock parts so soldered a trough hole one (1/4W, 1%):



And then console powered up fine but as stated by owner screen was blank but sound and controls worked fine (I could hear intro sound effects/music and start a game playing blind):


I installed the screen in my known working Lynx II and it just worked fine. And as expected my known working screen stayed blank in the faulty console. I also noticed brightness control (left wheel) didn't have any effect. Again I probed the involved circuitry starting from the pot of the left wheel, which lead me to few transistors on the right, etc. When I found a resistor (R53) that had been eaten by the original leaky capacitors. Although the console had been recapped it was too late and the board and parts in this area suffered slight damage. Fortunately marking was still legible (394 = 390kΩ) but it read 3.6MΩ. This time I found the appropriate SMD replacement in my pile of scrap electronic gear:


This brought back image, brightness control was now working:


Console fixed.



15 Aug 2018

Sega System 24 multi kit

It's a kit I designed for the Sega System 24 in order to play all games form one boardset.

I had to decrypt all floppy based encrypted games before (encrypted 68k CPU in FD1094 module):
- Crack Down
- Dynamic Country Club
- Gain Ground
- Quiz Syukudai wo Wasuremashita
- Rough Racer
- Super Masters Golf

And also patch romboard based games (security chip on romboard):
- Bonanza Bros
- Quiz Ghost Hunter
- Quiz Mekuromeku Story
- Quiz Rouka Ni Tattenasai
- Tokoro San no MahMahjan
- Tokoro San no MahMahjan 2

The kit is composed of 2 boards. A small one on that fits on the motherboard (contains all different "loaders"):



A bigger one that fits on the romboard:



And of course jumper cables to interconnect them:



And finally did test the whole library:














Few notes:
- Hot Rod and Rough Racer require the 834-6510 analog I/O board in order to boot
- The mah-jong games can only be played with the mah-jong panel
- Quiz Rouka ni Tattenasai requires the 837-7968 (or equivalent) 3/4p I/O board in order to boot

To fully use the kit you need:
- any System 24 motherboard with 2 standard 68000 CPU installed
- the floppy controller board (837-6643)
- any System 24 romboard (837-7187-xx)
- the System 24 analog I/O board (834-6510)
- the 3/4p I/O board (837-7968 or equivalent) if you want to play 3/4p player games (required by Quiz Rouka ni Tattenasai to boot) or the mah-jong games (it seems the dedicated panel needs to be connected through this expansion board)
- the mah-jong panel if you want to play the mah-jong games

9 Aug 2018

PGM slot - IGS (repair log)

This slot was given to me in exchange of my service for figuring out how to make Cave conversions on PGM hardware. Many thanks to the donator, my last PGM slot had been stored for too long with its original battery and leakage damage was extensive (way beyond repair) so ended up in the part bin.

The slot was said working if voltage was raised a little. This was indeed what I found too, slot required ~5.15V in order to boot otherwise it was stuck on a garbage screen:


This is absolutely not normal for any original hardware to not work correctly @ 5.00V (bootleg boards can be a different story due to shitty design and botched power supply planes). In the long term raised voltage can damage chips (RAM chips first especially after a lot of operating hours where their specs drop a lot, e.g. 5.5V max voltage can fall to only 5.2V). I've seen many old boards dying in front of me after the owner raised voltage to only 5.2V trying to clear a graphic fault when all of sudden KABOOM! More than often RAM chips die first. Also an increased voltage result in more heat having to be dissipated by all chips.

I started to have a look at the board and noticed a lot of corrosion points but nothing likely to cause a problem. After a while I found 2 traces which seemed severed. One was good but the other one showed a resistance of around 20Ω. This doesn't look much but probably enough to drop the carried signal to a critical point. I patched it with a bit of solder and booted the board again @ 5.00V:




Board fixed!

1 Aug 2018

Irem M72 multi kit - part 3

Small update.
Lightning Swords/Kengo is now supported by the M72 multi now. I've first decrypted it (originally runs on M84 with encrypted V35 CPU) and then converted it to M72 (work RAMs/video RAMs/palette RAMs offsets/mapping, IRQs handling, main CPU ports patching, sound CPU code loading and ports patching, flip/priority bits for tiles, samples playing, scrollx1 & scrollx2 offsets, etc.):


SPOILER ALERT!

And of course thoroughly tested it to the end several times (different difficulty, 1P solo, 2P solo, both players, etc.):