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

 

Terra Cresta repair log #2

 PCB Repair Logs, Repair Logs  Comments Off on Terra Cresta repair log #2
Dec 192016
 

I got this faulty pcb in change of some repairs.

The seller told me that the game was bought as working but after some time it developed a problem on the background with some repeated tiles all over the place.

I could confirm the behaviour, but after a couple of troubleshooting sessions the problem became worse and the background was only white.

The game has not schematics, so after some time spent to understand where the background generator was sitting I could isolate the problem on the ram@18D which had some data lines stuck low.

After replacing it, the problem remained but at least the ram had all the datalines working.

With the logic probe I then found a 74ls273@18E which had all the outputs in the grey area.

After replacing it, the background was fully restored