Capcom 1942 Repair Log

I found this cheap 'untested' original 1942 on evilBay a looooong time ago. Untested usually means tested but defective, but with the 'alternative description', sellers think that they can get more for their defective boards. This was actually one of first 5 boards I ever bought, and I was still young and innocent. So I was full of hope, when I connected the board for the first time. However, all that showed on the screen, was this static screen full of sprites

This was long before I even started doing reps, so the game was just put on shelf with the optimistic thought, that I might be able to fix it some time in the future.

At some point I snapped up another cheap original 1942; this one was working. So I tried swapping the secondary boards on the two and saw, that the working one with the secondary board from the defective, booted to this screen and was working fine.

...the other combo resulted in the same screen as before. So the static screen had to be caused by the primary board. So far so good.

Now about a year ago, I felt I had the courage to take a real look at this board. During the initial visual inspection, I quickly found this

This, the brown patches at each side of the edge connector, looked very much like the result of a major short circuit or some other type of overload. Also a cap was missing in the sound section, so a new one was fitted (easy, as the schematics can be found at porchys site jammacade.net)

Other than that, both PCB's looked quite sober and well. Next step was to dump the ROMs on the primary PCB, thereby also reseating them. However, when I got to the 5 ROMs SR03-SR07 I got either this

or this

Both cases meant that the ROMs were knackered...ALL 5 of them?!...you don't see that very often. So found the MAME ROM-set and programmed and fitted 5 new ones. Well actually I couldn't find any 27C128 in the scrap pile, so I used 5 27C256 instead. This is done quite easily: You make a ROM-image twice as big, by putting 2 copies of the original image after each other (in a Windows environment this can be done with the copy-command (with the /b option and '+' between the 2 source files) from cmd.exe; on nix-systems you can use the cat-command and pipe the result into a new file). That way it doesn't matter if the most significant address bit is high or low (or floats for that matter), because the same data resides in both the upper and lower part of the ROM; effectively making a 27C256 act as a 27C128.

I still had the static screen though. So next I checked the control signals on the main CPU: Clock, reset, halt etc. They all looked fine, but there was no activity on the main address bus neither the main data bus. This can often be caused by bad work RAM

so I desoldered them both to test them in the Top. They were both fried, so fitted sockets and found 2 replacements from the scrap pile

However it didn't change a thing on the screen, neither on silent buses. This was as far I got at that time, so back on the shelf it went.

A couple of weeks ago, I decided to pick this board up again. I had recently acquired my Fluke9010A, and this would be a perfect chance to use it };-P So started by desoldering the main CPU

and fitted a socket; notice that I don't use machined pin header strips, as the Fluke works better with standard sockets.

Next, let's power up that beast };-P

Now the first thing to do, is always the BUS TEST to see if any lines are stuck, floating, or tied together

I turned off the power and checked for direct connection between GND and data pin 3, but found none. So this was likely either a broken TTL, or the short might be on the other side of a mux, latch etc. Did a read-up on the schematics and found, that the first component on the databus after the CPU itself, was the 374 closest to the CPU. So desoldered it to test it in the Top, and was not surprised to see that the verdict was BAD!!!

So a socket was fitted and a replacement sourced from a scrap board.

Connected the Fluke again and ran the BUS TEST again. This time I got

Again consulting the schematics, I found that the next component on the databus was this 245 just beside the program-ROMs.

I had a tube of NOS 245's, so tried piggybacking one on top of the suspect

and now got the following result from the BUS TEST

...a clear indication, that something was rotten (in the State of Denmark };-P). So desoldered and tested it...once again a BAD!!! So a socket was fitted and the 245 from the tube installed.

(Yes I do know, that the 367 just beside it is now also socketed; I was a bit tired at the time and accidentally desoldered the wrong IC };-D When off-board anyway, I tested it in the Top, and it tested OK.) Now I finally got

With shaky hands I prepared the "RUN UUT"-function,

pressed the 'YES'-button, aaaand

It's aliiiive };-P Even though the start screen was olive green and not black, the attractmode played fine with no colour issues. Coined up the game and hit the start-button. Right upon start-up, the plane flew all the way to the right, but beside that, the controls worked fine. Turned the board off again, removed the Fluke-pod and reinstalled the original Z80.

Hmmm, could seem like the main CPU was toasted as well. Found an original Zilog from a scrap-board, installed it, and the board now worked just like when the Fluke was running it.

I decided to address the control issue first. By using the continuity tester, I traced the 'RIGHT'-pad on the edge connector back to this 367 at A4

As all these 3 367's are already socketed, it was an easy task to test it in the Top. It tested BAD!!! and a working one from scrap was installed.

Now the controls were perfect, so I had to address the olive green start screen. So far, I had only been concentrating my attention on the main PCB; now I turned to the secondary one, as this handles the graphics. As usual I did visual inspection, but found it in good shape. Next I started dumping the ROMs. But when I got to SR13, the Top reported unconnected pins...

So I sourced (scrap), erased, and programmed a new one with the image from the MAME ROM-set, and presto:

black background on the start screen restored };-P

Last but not least, I borrowed some of my wife's coloured crea-tape and made some lovely looking new stickers for the newly programmed ROMs (note to self: buy heart shaped stickers for future reps };-P)

As I have mentioned before, I can't stand the sorry excuse for music in this game, and I don't think much of the gameplay...so I will try to trade this board for some more defective ones };-P

Capcom 1942 Bootleg Repair Log

I got this board about two weeks ago when I traded an original 1942 for 4 defective bootlegs and some cash. I was told that the game was ok, but had problems with the controller inputs. When I got it, it looked like this

I'm pretty sure that there exsists a very special and particularly gruesome place in Hell for people who solder their adaptor wires directly onto the PCBs connector };-S It is just so cumbersome to remove them again... But after about 30min of hard labour, a good 20cm of solder wig, and a light scrub with rubbing alcohol and toothbrush,

I had a result I was pretty satisfied with.

Now, as this board has a 44pins pinout, it couldn't be Capcom Classic (like the original) for sure, so I grapped a 44 pin edge connector and a JAMMA fingerboard from the pile, and went hunting the net for the pinout. And at mikesarcade.com I found something that looked like it was the right one (notice the 5 consecutive GND-pins in both the pinout over at mike's and on the pic of the component side above). Even though I was about 99% sure it was the correct pinout, I built the adaptor in steps with supply + video, sound, and then controls, with testing in between each step. However after I added the controls, the sound was gone.

Hmmm, checked all the connections again and tried to wiggle the board i bit while it was running. I managed to get sound momentarily. Okay, so my adaptor was fine...the board had just developed a sound issue while I was fiddling with it.
Now on to the controls, that I've been told was screwed. First thing I noticed was, that the game started right after I hit the coin button. Next the plane used up all the rolls, then flew to the top of the screen shooting constantly.

The only control function responding, was left on the joystick. I started with the start button. First I found it at the edge connector, and a continuity tester confirmed, that it was tied low. Luckily I was able to trace it backward using only my naked eye. First thing it met, was this array of pull-ups.

Now the first resistor in the array seemed to pull up fine

But the next couple of them

was tied low.

However after desoldering, the array seemed just fine, when tested with the Ohm-meter

And (not all the surprised) I found that the pins were still tied low on the board.

So the array was going to be soldered back on the board, and I went looking upstream. The next thing the line met, was the 367 just below in the picture above, so out it went

And BINGO, it tested Bad!!! in the Top };-P

So fitted a socket and found a good 367 from a scrap board.

But when I then powered up the board, all I got was this screen of garble. WTF!!! };-S

Tried turning power off and on a couple of times, and even tried putting the old 367 back, but still same-same... Well, back to basics: Did visual inspection of parts and solder side for both PCBs. Reseated all socketed ICs and dumped all ROMs

All seemed correct there as well. Desided to hit the sack and sleep on it, as I was pretty tired.
When I got back to the board the next day, the first thing I noticed was this

Not all the dip switches on SW2 was fully off! I set them all off, and the game booted just like it had done before };-P After I had a look at the dip settings, it was obvious, that switch 1 on SW2 must have been on causing the whole game to freeze. Well lesson learned: If something really stange suddenly happens to your board, check the dips first };-P
Now, on with the REAL repair };-P The start button was now functional, so the game didn't start right upon being coined up anymore. However, the plane still used up all the rolls and flew to the top of the screen when starting the game. So traced the loop button back to a resistor array and a 367 just like with the start button. This time I started by desoldering the 367

and it tested as BAD!!! in the Top. So a socket and a new one from scrap was fitted

Now the game played perfectly, except for the missing sound, that is.
Missing sound can be caused by many things, but I usually start by checking the amp. This can be done by maxing the volume-pot and running your finger over the pins of the amp. If you hear a hissing sound, the amp is not totally dead. Here, there was hissing. As I had just done a Wonder Boy 3 Monster Lair Bootleg, that uses the same amp, I had the pinout right at hand. So poked the input with the scope, and saw a total flatline. Next I found the pinout of the two AY-3-8910 sound chips, and had a look at the 6 outputs (3 each) with the scope; again dead silent. Then started checking the datapins sitting on the bus between the two sound chips and the sound CPU (a Z80, just like the main CPU). AHA! data pin 3 was always low.

I was pretty confident (maby because that had just been the case with the control lines), that whatever was pulling the line low, had to one of the ICs on the data bus. So first I removed the ROM; easy as it was already socketed. Still stuck low! Next I suspected these two 374s

So they was desoldered and sockets fitted. But they checked out fine in the Top and the line was still low.

In the maintime, I had found that the sound circuit is identical to the one on the original. So by inspecting the schematics (page 3) found at jammacade.net, I could see, that the only ICs left on the bus, was the CPU, the RAM, and the 2 sound chips. Now, if the CPU was knackered, it had to be desoldered anyway; if not I could solder in a socket and have a great chance to try out my new toy, The Fluke9010A };-P So desoldered the CPU and fitted a socket instead.

And now....Fluke-time! (Ooooh, exciting!!! };-P)

The Fluke showed just what I'd discovered myself

So the CPU was innocent. Ofcause, I was not able to do any of the other tests until I'd solved the problem with the stuck data line. The only things left on the bus was the RAM and sound chips. However, before desoldering any of them, I desided to visually inspect the circuit lines of the bus just one last time. Then I found this...

This grounded soldering was very close to the stuck line, and when looking through the magnifying glass, I could see that it had taken a little hit at some point. So I gently made a cut with a Stanley knife to separate the soldering from the line...

And when I booted the game, I had sound again, also with the CPU back in place. };-P
But as I had the Fluke powered up, I did the BUS test

Found the RAM-space via the MAME source

and did the two RAM tests (short and long...beware, the long one takes very long time)

Finally I used porchys great little tool Fluke 9010 Sig Calc to calculate the signature for the ROM and do the ROM test

I find that the Fluke is nice and easy to work with, and that it has a lot more potential than what I've done with it here...I'm so very happy with it };-P

Case closed; I think I'll try to trade this board for some other defectives, as I don't like 1942 that much.