JAMMArcade.net – Page 39

Mag Max repair log

Repair Logs Comments Off

Jul 112018

This game had been in my collection for about 14 years. I decided to make a play but the game displayed a RAM NG text and didn’t boot

After checking the schematics I decided to prove rams and some devices but the signals were healthy

Thanks to Kale from mame team, I discovered that the game does a simple check but decrementing some values in ram and read them back.

Therefore I decided to desolder the program srams to check if they were good. The game has only 2x 2016 toshiba rams.

This brand is known to be not really reliable in comparison to others

After checking the first one I got confirmation that it was bad

I resoldered it and this time the game booted with RAM NG briefly shown and behaved strangely. You couldn’t shoot and parts of the scrolling was repeating.

I decided to desolder also the second one since the game still complained about the ram.

Also the second one was bad!

After changing also this one, the game was 100% fixed

Rolling Thunder 2 repair log

PCB Repair Logs, Repair Logs Comments Off

Jul 112018

Got this game for a repair.

At boot it displayed the following:

Using Mame source code with the memory map I could narrow down that RAM0044Eo20 was the colour BLUE ram

Desoldering it I could confirm it was bad

After replacing it I still got:

30TIP, 31TIP and 33TIP error

After discussing with Charles MacDonald he pointed me to the DUAL PORT RAM.

It checks if the last entry in RAM (460FFF) is zero, if so that’s an error (should be non-zero)
Then it checks if 460FF contains byte 6B, if it doesn’t that’s an error too

I started to probe around the dual port ram

Until I found a stuck bit on the Left side of the Dual port ram which came from a 74HC175.

After changing it, the game booted but still with TIP33 error which could be erased by pushing the start button.

TIP33 is the error related to the EEPROM which is not inizialized correctly or contain some corrupted data. Normally you inizialize it only one time but everytime

started the pcb, I got this error and offcourse all the dipswitch settings couldn’t be saved correctly.

To cut a long story short, some smart guy changed the original EEPROM with a normal 8k SRAM!

I took a spare from a faulty final lap 3 and I could finally fix 100% the game

Black Tiger repair log #3

PCB Repair Logs Comments Off

Jul 012018

Although this is a bootleg it follows the original PCB closely.
Couple of easy fixes on this one.
First a character issue and second a sound issue.

As you can see in the video above, the screen is filled with “A”s and none of the text is correct

There is a seperate EPROM used for characters on this game.

Pulling this and reading back with my programmer yielded a valid dump for Black Tiger.
Checking the adjacent associated 74LS273’s and 74LS245 showed I had at least one pin floating.
I traced this back to a nearby TMM2016 which had D7 floating.

Replacing this fixed the screen

The sound issue was even easier. The sound program EPROM was completely smashed. Replacing it fixed the issue.

Job done.

Taito MB112S146 custom reproduction

Reproductions Comments Off

Jun 122018

Recently I have been working on reproducing the MB112S146 custom chip for my friend BanjoGuyOllie.
This module is found on Arkanoid, Darius and probably some other titles too.
This has now been done and is available in the downloads section. It required the adapter board from ColinD but I will soon compile for MikeJ’s module too.
So far its only tested on Arkanoid but probably will never get a chance to test on other hardware.

PLD Archive news

General Comments Off

Jun 102018

The PLD Archive is currently in the process of being moved to a new wiki.
There may be a delay is adding new files while the wiki get populated. This is currently over half way done but the process is long and tedious bear with us.
In addition to the normal PLD files there is also scope to add more detail and pictures so if anyone has any good quality PCB pictures or extra information like missing PLD IC location details or names then please let us know.

The old table will be kept up for now until we are sure all the detail has been moved over correctly.
You can take a look at the wiki at
https://www.jammarcade.net/wiki

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