Corrado Tomaselli

No background in electronics. Learned everything by reading pdf books and expecially Video game logic Vol 1 by Atari and in general early Atari and Williams arcade manuals

Rolling Thunder 2 repair log

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

World Rally 2 repair log

PCB Repair Logs, Repair Logs Comments Off

May 052018

I got a dead World Rally 2 which upon boot showed garbage but I could hear that the monitor was hissing, meaning that there was no proper sync.

I immediately checked the two OSC on board and found the main one, 26mhz which is driving the 68k and pixel clock dead.

The 26mhz is not very common but I managed to found it on another Gaelco board and replaced it.

Game still didn’t start and was out of sync, but the 26mhz signal now was present

Near the OSC there is a 74ls74@IC29 which divide by 2 the clock for the 68k which runs at 13mhz.

The output of the flip flops was completely dead.

Replacing it I got this time a black screen with no activity.

First thing I did without much hope was to check the program eproms , normally it’s very rare that they fail but to my surprise both eproms had pin 31 not connected internally!

Replacing eproms with good ones fixed the game completely.

Last think I did, was to change the DALLAS MCU battery since it was at 2.9V , very near to suicide.

TumblePop repair log #1

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Apr 242018

I got this game for a repair:

The game had some background problems ( unfortunately I forgot to take a pic ) and a sprite problem:

The background problem was fixed reflushing the custom chip 56.

As for the sprite problem, after some time checking the part of the circuit responsible for the sprites, I found a couple of 6116 sram @D5 and D6.

One of them had some weak signals on the data lines and tested out of circuit it was confirmed as bad

After replacing the sram the game was fixed

Black Tiger repair log #2

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Apr 142018

Got a Black Tiger for a repair which had a colour problem on some graphics

It lacked some shades of colour

I decided to look around the palette rams @6C and 6D until I found a fixed address line

Tracing back I found an 74ls157 @5D with an output stuck low.

After checking the inputs I found one of them stuck low and according to its truth table, the output is always low.

Tracing back I found a 74ls273 witth Q3 output low and D3 input oscillating.

Piggybacking a good one restored the correct colours.

After changing it , the game was completely fixed

Psychic 5 repair log #2

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Apr 102018

My beloved original pcb developed once again problems after the last repair log you can read here:

Psychic 5 repair log #1

This time, the overall colour palette was pinked and all text was missing

After some troubleshooting I found again a problem with a Fujitsu ttl 74ls08, same type and week/year of manufacturing of the one I changed on the old repair log!

After changing it, the game worked fine for some minutes and then it developed a new problem

Game lost sync and became bluish

Again I decided to concentrate on the only Fujitsu 74ls08 ttls which were present on the board until I found the faulty one.

Same week/year of manufacturing and same fault: dead outputs

In addition, I found another couple of Fujitsu 74ls08 which had dead outputs and I decided to change all of them with good ones.

Now the game is 100% fixed but there are 3 more Fujitsu ttl waiting to be replaced. I ran out of parts otherwise I would have changed them immediately.

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