Auctions and After-Market Circuit Boards

Posted on December 1, 2022 by Randy

Auctions

If you’re looking for a used pinball machine, stay away from auctions. I have a number of customers who have purchased machines through various arcade related auctions that were in substantially below average condition. Perhaps the customers who get good machines from auctions don’t contact me which gives me a biased view. But the machines I have worked on that came from auctions have been atrocious (especially one with Captain in their name). Usually it’s a case of missing parts or bypassed functions so that the machine appears to be working but actually isn’t.

After-market Boards

It is usually much better to have an original circuit board repaired than it is to buy an after-market replacement. People wrongly think that if it’s new it must be better. But as more people repair their own pinball machines, the easiest thing to do is to buy replacement boards.

Over the years I’ve had a number of problems with Rottendog boards. They might be gradually improving, but I’ve had one problem after another with them. Here’s just a recent example. I recently purchased a new CPU/sound board (MPUWS) for a Sega, Lost World Jurassic Park pinball machine. Compared to the original board, a section of circuitry was omitted from the design presumably to save on cost. Needless to say, the board didn’t work in the machine. None of the optical sensors worked.

Circuitry outlined in red is missing from the Rottendog board. Most importantly the two LM339 chips on the left.

Rottendog board missing the comparator circuits (LM339) found on the original board.

The original board was suffering from substantial battery corrosion. In the end, I ended up removing the corrosion and repairing about a dozen traces on the original board and using it instead of the Rottendog board.

Another manufacturer is X-pin. I recently worked on a Back to the Future pinball machine made by Data East. The owner had an X-pin PPB board installed. The board had shorted transistor on it. This is a really common problem in pinball machines. X-pin chose to use surface mount transistors that are not field repairable.

X-Pin uses difficult to repair surface mount transistors on driver boards.

I have the special equipment to repair surface mount parts, but it’s not something I can drag with me to a customer’s home. Every pinball manufacturer uses through-hole technology in their solenoid driver circuits. Through-hole parts can easily be replaced in the field and by anyone who has decent soldering skills. The only reason X-Pin chose to go with surface mount is to save on assembly cost. I’m a former electronics engineer and have decades of experience with this.

Fortunately in this case, the owner of the pinball machine still had the original PPB board. I was able to get that up and running on the spot. I only brought back the X-pin board to my office so the owner could have a backup.

There are a few aftermarket board manufacturers that I have good experiences with. One is Alltek. They supply boards for the early solid state Bally and Stern machines. I’ve probably installed over 50 of their boards and never had a problem. Another manufacturer I haven’t had issues with is Ni-Wumpf who make boards primarily for Gottlieb pinball machines. Another is Flippp, which is a non-profit located in France which charges a little more, but they are great circuit boards. There are other manufacturers out there who provide true to original designs.

I come to my repair appointments ready to repair common problems with original boards. I don’t stock parts for the after-market boards unless they are using the same parts as the original. I don’t like it when after-market boards stand in the way of a successful repair. I only recommend using them as a last resort.

Last Action Hero Pinball Machine (Data East, 1993)

Posted on September 16, 2019 by Randy

Symptom: not playing the correct sounds, some sounds playing backwards.
Location: Parker, CO

The pinball machine was playing most of the sounds correctly, but the background music wasn’t correct and at times played backwards, and sometimes Arnold’s voice callouts weren’t correct either. The sound test from within the machine’s test menu worked correctly.

I checked the electrical signals between the sound board and the MPU board with the oscilloscope and they seemed fine. I began to suspect a problem with the sound ROMs, so I brought the board back to my office where I could verify them, and they were fine.

At this point I dove deeply into the history and operation of the BSMT2000 sound system, which was developed by Brian Schmidt in the 1980’s. Supposedly “BSMT” is an acronym for Brian Schmidt’s Mouse Trap. In any case, he developed sounds for many pinball machines in the 80’s and 90’s and also designed the sound system hardware. The hardware design was used by Data East, then Sega and then Stern. It’s basically a sample playback machine where the speed (pitch), looping, length and panning of a sound can be adjusted. From some of the sources I’ve read, up to 12 sounds can be played at once. It’s much like a digital sampling keyboard, but without the keyboard. The early boards were stereo with a center channel for the cabinet speaker. Later circuits have parts eliminated and only monophonic is supported.

Since most of the sound board was working, I decided to create a test ROM that would test the RAM and then exercise the interface to the DSP (Digital Signal Processing) chip. Everything checked out okay, but I still had a sound board that wasn’t working correctly.

As I was staring at the schematic trying to figure out what else to test, I noticed “W6” and “W7” jumpers, which are connected to A18 of the sound ROMs. On the schematic it says “W6 IS JUMPERED”. The EPROM sockets will accept 27C010, 27C020, and 27C040 (1 megabit, 2 megabit and 4 megabit EPROMs, respectively). Address line A18 is the highest address line for a 27C040 EPROM and when “W6” is installed, it connects it to +5V, which makes the socket only usable for ‘010 and ‘020 EPROMS. But Last Action Hero has a ‘040’ sound EPROM. So what’s happening is it’s playing correct sounds from the upper half of the EPROM, and when it needs to play sounds from the lower half of the EPROM, it sees a duplicate data from the upper half. The lower half of the EPROM is inaccessible.

W6 and W7 jumper locations below the EPROM sockets (or above the sockets if the board is installed in the game)

It appears the schematics were never updated for machines that used 27C040 EPROMs, nor any other documentation to explain when the jumper should be installed in W6 and when it should be installed in W7.

So the rule is this: Any pinball machine with the 520-5050-0x sound board that is using a 27C040 EPROM, the jumper should be installed in W7 and not installed in W6. Any other situation requires the jumper to be installed in W6 and not W7. Do not install the jumper in both locations at the same time. It’s one or the other.

Some other machines that use this board and have ‘040 EPROMs are: Rocky and Bullwinkle, Tales From the Crypt, and Jurassic Park. I suspect that someone acquired this board from an older machine like Hook or Star Wars and put it into this Last Action Hero, without having the knowledge of the W6 and W7 jumpers.

Another word of caution: I don’t think the BSMT2000 chips are the same across all the different sound board designs made over the years. For example, later sound boards have more EPROM sockets and the BSMT2000 chip would need to know that in order to utilize them. I don’t have any information as to tell the difference between the BSMT2000 chips and the version of the internal code.

Markings on BSMT2000 chip

Jurassic Park Pinball Machine (Data East, 1993)

Posted on August 14, 2013 by Randy

Location: Niwot, Colorado
Symptom: Smoke, GI lights not working, some switches not working

There were a number of burned connectors in the backbox. There were a couple associated with the GI lighting on the light board and the play field, and another connector on the power supply board.

I was able to re-pin one of the GI lighting connectors and the owner suggested just bypassing (removing from the circuit) the connector for the light board since it was unlikely that anyone would need to take the light board out of the backbox.

Burned connector, CN1, on the power supply board.

The power supply connector was problematic. I tried several ways to fix it, but it would just heat up and start smoking again. Part of the problem was the plastic had melted and mixed with the solder, making it very difficult for the solder to stick to the metal. I decided that it would be best to replace both the PCB mounted connector and its mate.

Fixing the connectors solved all of the power problems.

There were several switches not working. One had a broken wire. Another was mis-wired at a connector, making me wonder if it hadn’t left the factory that way. After everything was fixed, the owner and his son were trying it out and exclaimed they hadn’t seen various modes of the game previously. It hadn’t been fully working in the 10 or 15 years they had it.

Star Wars Pinball Machine (Data East, 1992)

Posted on May 28, 2013 by Randy

Location: Highlands Ranch, CO
Symptoms: Wrong wiring on switch and lamps, broken drop target

This is the first machine I’ve ever encountered that had an alarm system attached to the coin door. I’m pretty sure the owner wasn’t even aware of it.

Coin Door Alarm System

The switch on the shift lever (used in place of the ball shooter) was disconnected. The normally closed terminal of the switch had broken off. Normally this terminal is used to hold the diode. I re-wired the switch and diode and covered the diode and connections with shrink tubing.

There were a number of playfield lamps not working correctly. Some were staying on, some weren’t working at all. I found that someone had disconnected the “Jabba’s Bounty” overhead light on the playfield and twisted the wires together. This shorts out the lamp circuit. Once I un-shorted the wires and reattached them to the lamp socket, many of the other lamps started working. The remaining lamps were burned out.

The broken drop target was preventing the other drop targets from resetting. The stem was jammed in the reset mechanism.

I ordered a new drop target, which comes blank. There are Star Wars decal sets for sale on e-Bay, but they are missing the right target. The sellers suggests just taking the left decal and turning it upside down. I think it looks stupid.

e-Bay decal set with left decal turned up-side-down to make the right decal.

Here is a link to the IPDB showing the drop targets.

Since I have the old broken drop target, I decided to scan and print a new decal.

Scanned and retouched right decal image

New drop target on left, original on right

New drop target on left with my decal, original on right

The colors don’t match exactly, but I think it’s better than an up-side-down decal.

If you would like the high resolution files for making your own right drop target decal, they can be downloaded here. There are two .tif files contained in the .zip, one is the original scan without any touch-up, and the other is the touched-up version.

Rocky & Bullwinkle and Friends, Data East Pinball Machine

Posted on January 25, 2012 by Randy

Symptoms: Stuck flipper, flipper fuse blown, many lights not working.

The flipper circuit uses two voltages, one for pull-in (50V) and another for hold (8V). The transistor controlling the pull-in voltage (Q9) was shorted, leaving the high-power on to the coil, blowing the fuses. Replaced the transistor and the flippers worked.

I replaced many burned out lights. There are two rows of lights (in the 8×8 grid) not working. The transistors looked fried, and it looked like the board had also been hacked. Many GI lights on the backbox were not working too. Someone had re-wired some of the GI lighting bypassing one of the boards. Some of the ramp diverters are not working, so you never get the Hat Trick. The owner was not interested in fixing these issues! The machine needs to be “shopped”, but it is still being used in a bar.

Location: Denver, Colorado.

The Simpsons, Data East Pinball Machine

Posted on January 25, 2012 by Randy

Symptoms: Turbo bumpers not working, blowing fuses. Broken wire under playfield, loose playfield components, stuck switch on left slingshot, lights not working.

Machine needs to be “shopped” as it’s not in good working condition. Found shorted transistor that drives solenoid for turbo bumper. Replaced it, but it immediately smoked. Took a closer look at both the input and output sides of the drive transistor (TIP122). On the output side, discovered a melted solenoid under the turbo bumper. Replaced the solenoid. The bumper switch was ok. Checked the input side of the drive transistor and found the 2N4401 was shorted as well as the 7402 NOR gate IC was blown. Replaced all the bad parts.

The stuck switch on the slingshot was because the entire slingshot assembly was ready to fall off the playfield. Tighten it, repaired the broken wire.

Replaced many burned out bulbs. Backbox lights not working. Owner didn’t want those fixed.

When playing a test game, right flipper was getting stuck. The flipper shaft bushing didn’t have any screws holding it to the playfield. Found enough screws lying in the bottom of the cabinet to fix it. Flipper was still sticking. Took it apart to find someone had greased the flipper solenoid. NEVER DO THIS. Went through and tried to clean up all of the grease. Flipper worked fine after that. Overall the game is working. It is in a bar. The owner doesn’t want anything else fixed.