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Sunset Riders repair log #8

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Jun 042018
 

Was asked by a friend to repair his Sunset Riders.

When starting up the PCB, it was stuck in something resembling a watchdog fault.

But I’ve been working on Sunset Riders before and this didn’t seem like an ordinary watchdog. I felt that it went a little bit longer in the startup sequence before crashing.

The board was a bit dirty but I started with the usual:

  • Checking CPU signals like clock, reset and halt
  • Verifying the program ROMs
  • Checking the program RAM for odd signals

All looked ok, but then I found this at the 051550 reset signal generator.

Pin 1 on the 051550 looked like a cold solder joint.

Pin 1 is the clock signal input pin on this IC and without that input, I can understand that the game doesn’t boot up properly. Gave that pin a dab of solder

And booted up the game

Board fixed without any other issues 🙂

Robocop repair log #3

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May 162018
 

I got this Data East Robocop pcb from a friend that was totally dead.

I had more Data East pcb’s around so I could test the bottom ROM board with one of those CPU boards and it was also not working. So I started pushing the EPROMs in their sockets and after that the game booted up.

So now I tested the ROM board with it’s original CPU board and game booted but the screen was almost completely black apart from some graphical elements like the energy bar.

After visually going over the CPU board I found that one of the custom ASIC L7B0072 had a crack in the center of it.

I had a broken Midnight Resistance board (not the previous repair) that had this ASIC, so I opted to transplant it over to the Robocop board.

I noticed that the top of the ASIC had a brownish discoloration, but I didn’t know if it was toast or not, so I desoldered it with my hot air station and soldered it onto the Robocop board.

Confirmed that there were no shorted pins on the ASIC and booted the game, but unfortunately the transplant did not help. Some graphics appeared, but mostly scrambled characters and when coining up and pushing start, the game reset. (forgot to take a picture)

After having a conversation with caius (thanks again for all your advice) we opted to do another transplant but with a better looking ASIC.

Redid the procedure, hot air station to remove the ASICs and then soldering again and lo and behold, the game has good looking graphics once again 🙂

But I quickly noticed that there were no audio at all. Using my audioprobe I found that there were music been generated by the YM3014 at 4M and FX from the YM3014 at 3M and then going to the OP-AMP 3403 at 4N

Nothing came out of the 3403, so I eventually found that there were no +12V input on pin 4 of the 3403. Checked the JAMMA edge and found a broken track. I guess that the operator had some form of voltage measuring device and somehow broke the track at some point. I soldered a little metal wire to bridge the gap and booted the game again.

Now audio could be heard for a short second and then silence again.

I eventually found a shorted capacitor at 

After replacing the capacitor the audio was loud and clear again. Job done 🙂

 

Midnight Resistance repair log

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May 082018
 

I got this Data East – Midnight Resistance pcb from a friend.

He said that he dropped a ground wire onto the pcb by mistake and he thought it touched the pins on one of the L7B0072 custom ICs.

I booted the pcb and the game was running blind. Sounds and inputs was working fine, but a complete black image on the screen.

Been working on this hardware before, I knew that the palette RAM was located at J21 and J22, so I started checking their datalines with the scope

Hmm, zero activity

I then piggybacked a pair of new RAMs (6116 type) on top of the original RAMs

Voila, graphics are back 🙂

I then promptly desoldered the RAMs

and soldered a pair of sockets in their place. And the new RAMs

Job done 🙂

 

May 042018
 

Got this untested Konami Salamander from the UK

It was a little bit dirty, but still in good nick. No previous repair work and no broken traces.

First startup showed that the game was stuck in watchdog, so program code was not loaded correctly by the main 68000 CPU. But sometimes it would take longer to reset the watchdog and sometimes it also shouted out one of the speech samples.

So I first took out the program ROMs, shown below, and re-inserted them:

Now the game booted into ROM/RAM test. The screen is a bit garbled, but I could see when comparing to the test screen in MAME, that ROM6 was reported as BAD

I first verified the EPROMs against MAME and they were ok. So unfortunately there was a fault in one of the MASK ROMs. I had a Salamander board since before, so I just stuck the MASK ROMs from that pcb into this one to see if it booted up and sure enough it worked. The MASK ROM printed with 6108 was indeed not working.

As this is a MASK ROM, 1Mbit 28-pin, and not a standard EPROM, I remembered that system11 made a blog post about converting Salamander to the japanese version of Life Force. I have made that conversion as well, and still had some of the pcbs and flash roms.

So I just made one with the Salamander ROM.

And voila, the game is resurrected from the dead 🙂

 

No other issues, job done!

Feb 202018
 

Hi everyone, I’ve been a long time follower of jammarcade.net for several years and I’ve received a lot of help and advice from both Porchy and Caius. A big thank you to you guys! 🙂

Caius then approached me and asked if I wanted to contribute with my own repair logs of the games that I have resurrected from the dead and I thought that would be fun 🙂

So for my first post I thought i would document the repair of a Irem Battle Chopper. Pretty obscure and rare game that is hard nails, as always when it comes to Irem games.

The PCB was in pretty good condition but was missing some color. It displayed mostly blue graphics and faint red and green.

Having worked on M72 hardware before, I knew that color output was handled on the middle board in the PCB stack.

I started with measuring the RGB signals on the JAMMA edge with my oscilloscope, I could verify that the signal of R and G were absent.

Having access to the R-type schematics, I checked where the RGB signals came before it arrived at the JAMMA edge.

 

As you can see it derives from the custom KNA91H014. Bad news I thought, but when checking the outputs with the oscilloscope, all the outputs looked fine. So I then started measuring the resistance of the resistor networks (RA13, RA14 and RA15) and they also checked out ok.

Everything in that areo seemed to be ok, so I started to look more into the schematics and found this on the same page as the snippet above

When checking the outputs of this 74LS38 at location IC67 with my logic probe, I could see that red and green were floating. And I could also verify that they were both shorted to ground.

I then desoldered the 74LS38 and could then verify it as bad in my TTL tester

These 74LS38’s aren’t that very commonly used on arcade pcbs, at least in my experience, so I needed to wait for a replacement to arrive. In the meantime I added a socket on the PCB for easier access for the future.

With the replacement in place, I booted up the game and lo and behold, all colors are back 🙂

A good and rare game back in its full glory.