JAMMArcade.net – Page 119

Atari Asteroids repair log

Jan 282016

I was recently sent an Asteroids PCB which I had previously bought back from the dead, the PCB had developed distorted vectors but still running.

Here is what the TEST screen looked like, the actual diamond shape was perfect but text was oversized and distorted;

IMG_20160128_242023439

The actual GAME mode looked worse;

IMG_20160128_241959634

Check out the giant asteroid!

I knew the problem was in the Vector State Machine (VSM) area, specifically the area which is responsible for handling object vectors, so I looked there first.

It was not long until I found a decoder (LS42) at 7E which seemed to have some pins stuck LO;

IMG_20160128_242035901

I desoldered the decoder;

IMG_20160128_242531687

I tested the decoder in my IC tester;

IMG_20160128_242615090

I then socketed and replaced with a fresh decoder;

IMG_20160128_243027782

Asteroids now fully working;

IMG_20160128_243034333

IMG_20160128_243046130

PAL dumps update

PAL Updates Comments Off

Jan 272016

Today we have some new PAL dumps.

I dumped the specific PAL present on a Konami X-Men 6 Player revision.Board has in total three PLDs, two are in common with the 4 Player version and they were already on our database while this one was unique.

Lastly, I dumped four PLDs from a Funky Jet PCB, board has six devices in total but two of them were registrered.All dumps have been successfully tested on GAL16V8 targeting device.

28 pin CPLD replacement

General 3 Responses »

Jan 242016

Some years ago MikeJ from FPGAARCADE made a 28 pin CPLD replacement that could program to replace certain custom chips from a variety of arcade games and even the Commodore 64 PLA.
While I was waiting for Mike to get another batch of his boards ready, ColinD on the UKVAC forums contacted me telling me about his own project.
The concept is essentially the same as Mikes but his was originally geared towards replacing the SLAG chip on some Atari games. It does however have multiple links available so it can be configured into what we call ‘normal’ mode. This makes it so the power pins are in the corners like with ‘normal’ chips/EPROMS/etc. It also has space for a 3.3v regulator so a XILINX XCR3064XL CPLD can be used in place of the EPM7064 that I’m using.

20160123_115449-1

big_slags

My first project for this was to reverse the Konami 501 custom chip. Luckily I have a one of the bootleg versions of Time Pilot here courtesy of Muddymusic that has the same layout as the original board but all the customs are implemented in TTL on riser boards so reversing this was a matter of drawing out the schematic.
I eventually got something that let the game boot and work but there were some graphics faults here and there. This ended up being an issue with using a modern part to replace old parts. The propagation delay on the CPLD is a lot less that the original TTL part. This was solved by enabling the ‘Slow Slew Rate’ option in Quartus II.

So with the 501 reversed and the chip I have confirmed working I’ll set about doing the others on this board.
I’ve yet to test them on genuine hardware but I remain hopeful.

The original thread of Colin’s can be found here.
If anyone is wanting one of these then you can PM user ‘ColinD’ on the UKVAC forums.

Gryzor repair log #2

PCB Repair Logs, Repair Logs Comments Off

Jan 232016

A friend got a Gryzor PCB working but with problems on some of the sprites (mostly enemies and items with half of the horizontal lines missing).

The 4 GFX MASK ROMs were tested ok on another Gryzor PCB. Looking with the scope on the RAMs revealed nothing really suspicious.

I then piggybacked the RAMs around the GFX part and quickly found the faulty one.
It was the NEC 8644FU12 at location 14G. This RAM is a 4464 (64k-word x 4-bit, same type than the ones I replaced on my recently repaired Final Star Force).
Here is a picture of the PCB with the faulty chip highlighted in red:

gryzor2-1

Piggybacking it with a compatible TMS 4464-12 restored all the sprites.
In fact, the problem was so small that it was impossible to see any suspicious signal on any of the pins of that RAM with the scope (every signal looked healthy). I replaced the chip and obviously got the PCB running perfectly.

Here is a before and after picture:

gryzor2-2

Blandia PAL dumps added

PAL Updates Comments Off

Jan 172016

Yves_M, one of our members, sent in dumps of PALs from his Blandia PCB.Dumps were obtained from protected PAL16L8 and have been successfully tested back on board onto GAL16V8 targeting devices.Thanks to Yves_M for his contribution.

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