Closed for Vacation! No Shipping from 6/14/19 to 6/24/19

We will be away for vacation Friday, June 14th, through Monday June 24th, 2019. Our website will remain open, but orders will NOT ship until we get back on Monday June 24th, 2019.  Thanks for your understanding and patience.


Articles & Guides

Minefield Board Repair Log

I've always been a big Stern video game fan, still own a Minefield upright and picked up another Minefield board a month ago. The board was sold as untested, was hopeful it would work, but it came up with video issues as shown below.

The board did appear to play, just  hadscrambled video that was scrolling a bit as well.  Minefield boards are basically modified Scramble boards (and probably other classic Stern games).  Dug out my Scramble schematics and after 10 minutes realized that my VSYNC signal was missing at 8L and 9D, but present at 8L.  Quick visual inspection showed a damaged trace that I jumpered.  The board's video looked much better but was still rolling and not locking in. Tried it on another monitor and it did the same thing.  Checked my work and there was also a second trace that the gouge took out. Fixed this one as well and the board fired up perfectly as you can see.

One of the golden rules of board repair is always do a visual inspection prior to starting work, I did do one, but apparently not well enough as I didn't catch the broken trace until some troubleshooting work.

Mappy Board Repair Log

Spent some time working through a few Mappy circuit boardsets today.  Always loved this game, I still own one, unique cabinet and a pretty fun, quirky game.  Anyway here are some repairs from today and a few from a few years back.  I always recommend carefully removing and cleaning the legs on the custom ICs on this board. As you can see most issues were fairly straightforward, these boards seem to hold up pretty well over time. Enjoy!

Low sound - bad C30 cap.

"MAPPY" logo distorted on title screen - 4M Custom Chip on video board had dirty legs, cleaning them solved the problem.

No text on titles scren, etc. - Rom 3B on video board had a bent leg that was not in the socket.

No sound - amp was humming, so I suspected something else.  Prom at 3M on CPU boardset was bad.

Ram 3 Error - manual pointed to 6116 Ram at 2N, but replacing it didn't help.  Also tried ram next to it at 2M, no change, but sometimes it would boot okay.  Replaced both ram sockets for good measure.  Still booted with Ram error at times.  Kicked up the voltage from about 4.9 VDC to 5.1 VDC and board booted everytime.

Color Issue - Looked prom-ish, sure enough Prom at 5B at one leg out of socket.

No Sound (no hum or "audio pop" on boot) - Replaced by C29 and C30 as one looked iffy and a bit worn. Sound came right back.

That's all I have for now, probably will be some time until I get back to these boards, but hopefully this is of use to somebody someday.

Two Spy Hunter CPU Board Repairs

Picked up two complete Spy Hunter sets in a recent bulk buy, both were pretty clean sets, but not working. By swapping with a known working set (always highly recommended) I narrowed the problem down to the CPU boards on both of them.  Both repairs were pretty straightforward, but I'm not complaining, here goes:

Board booted with horizontal lines (see picture below) – Clean boardset, while looking at the socketed chips I noticed that the leg 15 on the rom at location 5A was not in the socket. Reseated the rom properly and the video issue disappeared.

Board booted with a few graphic lines, mostly blank screen – Starting swapping out socketed ICs, the Z-80, Z-80 CTC and 6116 rams were all okay. Moved onto the program roms and found leg 15 of rom at 7D was not in the socket.  Reseated the rom properly and the board came right up.

Two Marble Madness Board Repairs

Been a while since we've come across any Marble Madness items, we were lucky enough to pick some up in a recent parts buy.  We do have a System 1 test rig in our shop so I was able to test both Marble Madness cartridges that we found.  One booted right up, the other one came up with "Rom 20000 Error U".

Manual indicated this error was 15E, but that didn’t correspond with the version of the cartridge I had (there are different versions of these carts, the chips are laid out differently).  Checked the manual and determined it was a program rom at B12 by looking at the rom part number. Burned a new rom and the board then booted to 6502 not responding error.  Did some rom swapping and found a bad sound rom at D16, replaced this rom and the boardset worked.

While in the middle of swapping chips with our good board it developed a graphic issue.  Very frustrating as the board was working, starting pulling roms and checking them against the Mame files using our rom burning.  All of them tested okay, retested the boardset and it worked.  Guess all it needed was one of the roms to be reseated.

I must admit it has never been my favorite game, probably because I'm not very good at it, but it felt good to get these boards going again, I'm sure both will make some collectors very happy.

The Pit Board Repair (No Sound)

Was asked by a buddy of mine to take a look at his "The Pit" boardset. He actually picked up a dedicated The Pit, fairly hard to find game these days.  Anyway the boardset was working, but no sound.

First thing I noticed was the AY-8910 Sound IC was installed backwards, replaced it with a known working one hoping for an easy fix, but no luck. Swapped the sound Z-80 processor and the sound rom into a known working board that I happen to have. Both tested okay, so it was something more involved.  I did hear the typical amplifer pop or buzz so I figured the amp was working.

Used my scope to determine that the sounds were not making it to the amp by comparing it to a working board. Dug out the schematics and figured the 2114 rams used in the sound circuit would be next possible culprit.  I noticed when looking at their outputs, things didn't look right. Removed the one at IC20 and installed a new 2114 and the sound was working, although it would cut out or get distorted after a short bit. Replaced the other 2114 at IC21 and the sound was rock solid. Boardset fixed!

The Pit is definitely an interesting game, game play is a bit lacky and clunky but still a cool oddball classic game that you don't see much.