Triforce Type 3 repair (video problem)

Slowcade on ukvac forum asked for help with this Triforce motherboard that had an image problem. I offered to lend a hand, any excuse to play with a Triforce. :)

The problem was the video output had black bars going through it, a google search brings up two or three other people with this problem but not much else.

I was convinced before it arrived it was going to be a overheated GPU problem but once it arrived this was quickly ruled out after plugging the gamecube board directly into the TV and it having no image problem. That's right these Triforce boards use a standard japanese gamecube motherboard, the only difference is the IPL (BIOS).

 This is what the image looked like both in 15k and 31k mode.

Next I wired up Red, Green and Blue from the input pins of the Sony CXA2067AS (video amplifier) on the bottom PCB directly to the monitor and taking sync from the vga socket (sync doesn't go through the amp).

No more black bars, so the amp is bad right?

I also isolated the three output pins from the board to confirm nothing after the amp was causing the problem and it wasn't. So I ordered a replacement CXA2067AS from China, after waiting a couple of weeks for the replacement it ended up making no difference, and the black bars remained. It's possible the chip from China was bad as these are now obsolete it could be a pulled / used and untested chip but I am not so sure.

Either way I wasn't going to wait another two weeks for a replacement and decided to use what I had on hand. I bypassed the original Sony amp and used a TMS7314 amp which I already had from previous N64 rgb mods that you can find here.

Not pretty but it did the job.

Ready for some Mario Kart GP goodness. :)

Although 'fixed' I didn't quite get to the bottom of the exact cause with this one. If it wasn't a bad amp I believe it has something to do with settings stored on it, but this isn't confirmed.

Vic 20 Repair

The Vic 20 was dead and only showing a black screen, I wasn't expecting to have much luck with it either because from what I've read it's usually the custom CPU or VIC chip that dies in these. I didn't have another Vic 20 or any spares but I gave the motherboard a quick looking over anyway and checked the socketed chips were making good contact.

Before putting it back together and storing it away I noticed the previous owner had socketed three logic chips near the cartridge socket, 74LS374 if I remember correctly. I decided to swap these around since they were all the same and to see if it made any difference. To my surprise this brought the computer to life with just some minor graphics glitches, after replacing the bad TTL it is now fully working.

Wow I thought jailbars on the Mega Drive were bad...

Commodore 16 Repair

Taking a break from pinball restoring to fix some old computers (next update a Vic20). I have had this C16 in the to fix pile for over 2 years, I suspected the CPU was bad but I didn't have a spare to confirm this. I recently got a Commodore Plus/4 in a job lot so was able to take the CPU from that and confirm my suspicion.

As nothing is ever easy this didn't quite fix the C16, it would only boot to basic about 1 in 5 times of power cycling the system. It would usually show a black screen or a screen of garbage. Even when it did boot to basic it didn't behave quite right, for one the reset button did nothing and loading from a cassette wasn't working as it should.

I followed the trace from the reset button to the other end of the board to a LM555 @ U10 but this turned out to be fine. Next to it is a 7406 @ U9, after replacing this everything worked as it should.

 

 

Simpsons Pinball - Shooter

The shooter / plunger had been used for a long time without a rubber tip this has caused the end to 'mushroom'. As I was unable to take the shooter apart like this I used a dremel to sand it while still inside the machine. I held the dremel stationary and slowly turned the shooter.

 

Simpsons Pinball - Bad connectors

A common problem on Pinball machines is burnt molex connectors due to the long hours they were run for and heat build up.

What a mess, notice the wires connected to the test points. These go to the new coin mech as this was originally an american machine. I am sure there must be a closer gnd / 12v source to tap into rather than the backbox and directly to the power supply.

 

New 9 pin header installed and recapped the power supply.

Hmm toasty, this connector plugs into the playfield power board (PPB).

 

Replaced both connectors, the label maker also got a workout.

Data East PPB Board

I have been after a Simpsons Data East pinball machine for years and when one came up locally I couldn't resist. Although it was bought as working it still needs quite a bit of work, mostly cosmetic but also some board repairs, replacing connectors etc. Anyway lets get started, while changing all the fuses to the correct values I noticed a bad fuse holder on the PPB board.

CPC sell a replacement the part # is FF02911, it is pretty much identical to the ones Data East used.

 

For some reason Q4 has been removed, maybe to replace Q5 and they didn't have a spare TIP36? R16 was burnt so was replaced with a new 200ohm 1/4 resistor. I have ordered a TIP36 along with some molex parts more to come soon.