Last year after a lot of research I succeded to buy at a good price an original board of Psychic 5 , one of my favourite game of all time, which was really in mint conditions.
Some days ago I picked it up for a play and after some minutes the game developed this problem during attract mode:
After some more time the game was total yellowish:
Game hasn’t any schematics available and there are not any games known to me which have similar hardware and schematics available.
I could only go blind and try to find the reason of the fault.
So I started to short some signals of srams looking for palette changings and I found a couple of them at pos.6N and 6M, 16kbits.
The one at pos.6N had the first 4 data pins low and I was pretty sure either it was faulty or the 74ls245 connected to the data bits.
After desoldering, the sram 2018 was tested good in the programmer. That meant that the programmers didn’t use all data pins of the palette rams. The 74ls245 was good because it could drive correctly the signals without the ram installed.
I tested some TTLs nearby looking for strange signals but found nothing.
Decided to go brute force using my logic comparator and testing everything on the video board but starting with FUJITSU parts which are known to be very unreliable.
The logic comparator found a 74ls08 with all the outputs faulty
I double checked the outputs with a logic probe and they were all in the grey area (no good logic signal).
After changing it I fix the problem 100%
So FUJITSU brand proves once again to be really unreliable!
6 Responses to “Psychic 5 repair log #1”
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Great write-up! Great game! };-P Only a boot myself though }:-(
thx!
Hi,
I’ve got dozens of faulty boards made 95% of Fujitsu chips…
In your opinion does it worth repairing them?
It’s a lot of work (200 to 300 chips to remove for each game).
changing all the chips without knowledge doesn’t make sense. It is a lot of work.
You should start to test the Fujitsu TTL chips first
I think you didn’t get it, what I meant is I do know all those boards have several faulty Fujitsu chips (very easy to diagnose as they have a lot of floating pins). Knowing their poor reliability, is it worth replacing all of them (the Fujitsu one) as they will probably fail soon?
For instance in the past I’ve repaired games with faulty Fujitsu chips but didn’t replaced them all. After playing the games for few hours other Fujitsu chips failed. I also put some games which were 100% perfectly working on the shelf and few years later they were faulty again due to other Fujitsu chips that have died…
100% of boards I’ve repaired that contained Fujitsu chips had at least few dead Fujitsu IC so I think reasonable to think they will all die soon.
Ok, now i get it! your suggestion makes sense but it is a lot of effort with some boards. personally I am lazy to do this kind of work, so normally i replace only the faulty IC. If it has again problems i will start to look for other fujitsu chips first.