JAMMArcade.net – Page 69

Data I/O 29A & Unipak2 repair log

Jun 072017

I bought this setup from a good friend quite a few months ago now. I knew it needed some attention when I bought it.
On power up I got this most of the time
https://youtu.be/tzGoiafa2Wk

No response from any inputs from the keypad.
The keyboard generates an interrupt for the 6802 CPU. Using the scope I could see the /IRQ signal was being asserted.
I checked all of the ROM’s and found no issue and also checked to surrounding logic and found no issue.
Looking around the main PCB I found a couple of problem areas.

As you can see, both of these chips had some corrosion. I replaced them but they made no difference to the problem I had so after a while I came to the conclusion the CPU must be bad.
Searching eBay turned up nothing UK based so I fired off an email to my friend, Purity to see if he had a spare I could buy. He had one and said I could have it.

And now I get this
https://youtu.be/BgGFMV-0hL4

Problem solved.
Next issue was with the Unipak 2 itself.
I could successfully select and read chips but the data being read back was a little wrong.
Reading a few carefully selected addresses of an EPROM I found that bits 2, 3, 4 & 5 were stuck high.
Looking at the schematics I quickly came to a potential problem area.

You can see from the schematic above that the LM339 comparator is responsible for those exact bits.
I removed the chip and tested it out of circuit. The chip failed and I ordered some new ones.

With a new one fitted everything was back to working status.

I’m really happy to finally have this in my collection and working.
Massive thank you to Purity for his generosity. He has been very kind to me recently and also a great help. I hope one day to be able to return the favor.

Sega 171-5468 reproduction PCB

Reproductions Comments Off

Jun 072017

A good friend of the site, frsj8112, has reproduced the MCU bypass PCB that Sega used on some of its games and he wanted to share his work.

The PCB’s can be ordered direct from OSHpark HERE

Huge thanks to frsj8112 for creating and sharing this. Im sure it will help many people out.

Terra Cresta bootleg PAL dumps verified and redumped

PAL Updates Comments Off

Jun 042017

Having a working Terra Cresta bootleg (from Tecfri but they are all the same) gave me the opportunity to verify the PAL dumps we had.I successfully converted from PAL16R4 to GAL16V8 fuse map two of them.The third one was a native dump from a PAL16L8, the fuse map we had was not good so I redumped the device from my board and successfully reversed it in GAL16V8.Most likely, like it often happen for bootlegs that have same layout of original, the dumps should be working also on the Nichibutsu board but a real test is needed and would be appreciated.

Money Money PAL dumps added

PAL Updates Comments Off

Jun 032017

Some days ago I dumped the PALs from a pretty rare board : Money Money by the italian Zaccaria manufacturer.Here’s how board looks like:

Devices were three secured PAL16L8.I reversed two of them in a GAL16V8 while I was able to fit equations of the third one in a GAL22V10 (so tie pin 10 to pin 12 of the IC when installing the replacement in a socket).

Defender repair log #1

General, PCB Repair Logs 1 Response »

May 252017

I got for my collection an untested boardset of Defender which was really in great conditions with no battery acid leak.

The boardset is the newer revision of Defender with the red label roms.

The game is very difficult to find it in working conditions nowadays because it has several weak points, expecially the 24 drams 4116 which are very unreliable to due the fact the run very hot and they require +5V, -5V and +12V to be applied at the same time, otherwise they will be damaged.

The old Williams PSU become defective and often they ruin the drams.

After converting it to Jamma and triple checked all the power supply lines I booted it up but the game appeared to be dead.

Fortunately Defender has a lot of bibliography and a very good manual which is also a troubleshooting guide.

I check the clock and it was working correctly, but after checking the reset line I saw it was pulled low all the time.

To make it short, Defender has two +12V power supplies, one regulated and one not.

You have to supply +12V also to the not regulated one because it is needed for the power on reset.

After adding that +12V t, the game booted but as soon as the message ALL UNIT OK was displayed it reset in a never ending loop.

I found out that the problem was caused by the ribbon cable , after reseating it a couple of times, the game booted correctly.

I started the game but the ship kept always going down.

With the test menu , it reported that the down direction was always pushed.

I checked the interface board which has the circuit for the inputs. the hex inverters 4049 were all toggling correctly, the pull up resistors were good therefore there was only one chip to check: the Peripheral Interface adapter 6821P.

I desoldered it and installed another one I had on stock taken from another arcade games.

Since I had no way to test it, I decided to put a 40 pin socket just to be sure I could easily swap it with another one in case it was defective.

Luckily the inputs were now correct, thefore I could declare the board fixed.

In the end I was very lucky because the game had only the input problem and no other issues.

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