Repair logs

I recently bought a job lot of 16 faulty boards plus I have all my other faulty boards I've collected over the years scattered every where.

So I've been in a hurry to repair boards and get them sold just to make some space, because of this I haven't really been thinking about logging the repairs or taking pictures.

I have covered as much as I can remember but that's why there's no pictures this time.

Shinobi
No sound apart from 'mission one' when you start a game otherwise completely silent. A note on the board said 'probably YM2151' but looking at it on the scope all pins looked very active, the near by YM3012 on the other hand had four dead pins. Piggy backing a pulled 3012 from a scrap board brought all sounds back.

Street Fighter 2 World Warrior (Bootleg)
Lots of missing sounds, sounds playing randomly, noise / static and missing the colour red.
Looking on the bottom of the board there were some pins that looked like they had little to no solder on them. After soldering them properly red returned. As for the sound I suspected the yamaha chips at first as these bootlegs use fake chips. Turned out to be the surface mount OKI 6295 chip, I took one from a scrap CPS1 board.

CPS1 Motherboard
Game running but screen is blue and nothing is visible.
All four 6116 palette rams near the edge connector bad. Depending on the board some times it's 2x 6264 rather than 4x 6116.

CPS1 Motherboard
Board would always lose sound after a few minutes.
This one was a real bastard to find, I thought it was going to be a thermal problem and something was failing as it heated up. I thought the most likely candidate would be the z80 cpu as capcom fitted a standard z80 instead of a z80a. Then I tried replacing the amp, still no difference. I recapped the entire sound section still no change. I was about to give up but thought what the hell and replaced the z80 crystal even though I've never had a crystal fail on me before apart from ones that were physically damaged. To my surprise this actually fixed it.

Commando (Capcom)
Bad background graphics.
The only fujitsu ttl on the top board a 74LS30 if I remember correctly, replaced and problem fixed.

There have been several other repairs but simple trace repairs and ram replacements.

Gun Smoke (Bootleg) repair

I bought this bootleg Gun Smoke board years ago but a colour prom was missing and as I had no way to burn another it has pretty much sat waiting for a prom ever since.

Time to deploy my new favorite toy that I picked up from ebay a couple of months ago.

Stag System 3000 (cira 1991)

This beast of a programmer can program many chips but most importantly for this repair it can do bipolar proms.

I usually use it on an old laptop in dos connected by serial cable but as I had an original Gun Smoke pcb as well I decided to copy the original proms directly rather than try and find the correct files in mame. Turn the key and you're in standalone mode, copy the content of the original prom and burn it to a new blank one which took a total of about 8 seconds.

When the prom was missing the screen was all red (which I forgot to photograph) but just think of a virtualboy game.

After installing the new prom the game looked a lot better but there was no green, checked the green pin at the edge connector with a meter and sure enough 0v. Traced it back to the prom next to the new one, pin 12 had internally shorted to pin 8 (ground).

Bad prom removed.

I did the same as before to replace the missing prom by simply copying the one from my original board and burning it to a new old stock 82S129.

Green restored, repair complete.

Crazy Kong repair

This board had two faults, various graphics glitches and noisy / incorrect sounds playing. I started with the graphics fault first as thought this would be the harder to find.

At the start of the game Kong climbs a ladder, the sprite was messed up, Mario looked weird when moving like he had a broken leg and when he got to a certain point on a ladder he turned into a blue ladder.

After ruling out the usual suspects (bad traces, eproms and fujitsu ttl) I was left looking at all the other ttl, and there's a lot of it. The Gauck comparator probably would have saved me an hour or so but unfortunately I haven't even started to build it yet. 

Since the fault isn't constant it was tricky to track down, I decided to crash the game at a point where it was glitched, I did this by bridging two address lines on the Z80. Then went around the board with the logic probe and hp comparator, I eventually found a 74LS273 @ D2 with output pin 16 stuck low.

It's not a Fujitsu for once.

I replaced the 74LS273, Kong is now restored and Mario can run and climb ladders without disappearing once again.

This just left the sound issue which was a simple one, I replaced the AY-3-8910 chip and all sound was restored and played correctly.

Bank Panic repair

I've had this board for years, I got it when I cleared out a local operator. I always thought it was a puzzle game for some reason but after watching game play of it on youtube I finally decided to dig it out and make yet another jamma adaptor.

The label maker ran out of tape. :(

When powered up I was greeted with a black screen and no sound. Checking the cpu (Z80) with a logic probe I could see the reset circuit was working as it should but there was no clock, it was stuck high instead of pulsing.

Looking at the crystal it looked fine, and not snapped off as I often find them. Looking slightly above the crystal I see a Fujitsu 74LS74.

The comparator flagged pins 5 and 6 (outputs) as bad.

Piggybacked a good 74LS74 on top.

and it fired right up.

Unfortunately after about five minutes of playing the game, it crashed and reset then refused to work at all.

Looking over the board again I spot more Fujitsu.

 Another 74LS74 and again it flags the same two outputs.

I was going to replace all the Fujitsu anyway, it's like they knew and committed suicide as I found two more bad 74LS74s.

All Fujitsu removed and replaced.

The board is back to working.

The sound was a bit scratchy and quiet but after replacing the 3x 220uf 16v caps in the bottom right corner of the board the repair was complete.

The game is surprisingly fun and addictive, defiantly one for the collection.

Donkey Kong Jr (Good working order)

I just picked up this Donkey Kong Jr board from ebay, described as good working order. It certainly wasn't by the time it made it to my door step, it didn't help that it wasn't even put in a box. Bubble wrap and brown paper... typical ebay.

I didn't bid much on this as I thought there was a good chance it probably didn't work given that his Nemesis board was listed as untested / unable to test.

I did think it was an orignal Nintendo board though as it looked the same as an original from the low res pictures and I didn't know bootleggers did 1:1 copy boards. Turns out they did, all they changed was adding an audio amplifier and out putting standard video instead of inverted. This is better in some ways but it also means I cannot use my Mike's Arcade Nintendo to Jamma adapter.

First thing I had to do was wire up an adapter.

I've had to made a lot of these over the years and it never gets any less tedious.

Before hooking it up I had a good look over the board, I noticed a pad was missing on the edge connector, looking at the pinout this is Green. So it is going to need to be sorted, I lifted a pad off of a scrap board and glued it down then ran a small piece of kynar wire. 

It's not winning any beauty contests but it'll work.

I power it up and got no sync, this is a common problem on original board too. I knew this already from a previous repair, the pots on the bottom board get damaged and the board won't sync. This can happen when you post it without putting it in a box first!.

Resoldered the two legs that had lifted on the vertical pot.

 Things aren't looking good

or working.

Now I decided to reseat all the EPROMS and check them with romident while I was at it.

EPROMs 7E and 7F both had data romident didn't recognize.

These EPROMS didn't look original to the board, looks like they were just thrown in to complete it. Testing again sorting these two roms didn't help much.

After looking at the 2114 rams everything looked ok so I decided to go Fujitsu spotting. These two 74LS74s on the top board were the first two I looked at.

I stuck the HP Comparator on the top chip (7F) as it was right next to me and even had the 7474 card in it.

It lit up like a christmas tree.

I removed and replaced both 7474s as they were together and both Fujitsu but only 7F was bad.

It looks like MacGyver has worked on this board at some point, what do you do when you lose the pcb spacers?

 Melt a bic pen and hold the pieces in place with wire of course.

Replaced with some cheap spacers from China.

 There was also this strange ram bodge.

He looks so lonely.

 Game is now in good working order.

Desoldering and Fujitsu TTL

I desoldered all those nasty sockets from the Hyper Olympic / Track & Field board mentioned earlier.

Which unfortunately made no difference to the operation of the board, but it needed doing. I have a feeling I have at least one bad faulty custom chip but the board is littered with Fujitsu logic so maybe not all hope is lost for saving this one.

Speaking of Fujitsu logic while I had the desoldering station fired up I decided to remove all the evil F chips from an Aliens board that just constantly resets, to see how many were bad.

Out of the 29 Fujitsu chips 'only' three of them were bad (the three on the far right). I've got a couple of TMNT boards that will get the same treatment eventually but I need a break from desoldering after this lot.

Kung Fu Master PCB Repair

I bought this non working original Irem Kung Fu Master pcb from griffo on ukvac forums. I've always liked this game since playing the NES version loads back in the day, I actually like the sounds better on the NES but obviously the graphics are a lot better in the arcade version.

This is what was displayed when hooked up.

It's Z80 based board so time to hook up the fluke.

The fluke failed to test the ROM and RAM.

So I had a look at the logic between the CPU and ROM/RAM.

Four Fujitsu 74LS367s

Fujitsu TTL is well known to fail far more than other manufacturers for what ever reason. I decided to remove all of them now as even the working ones will fail sooner rather than later. I also replaced a Fujitsu 368 next to the CPU which just leaves three more F chips on the board which I will order and replace at a later date.

Thomas is back to saving Silvia.