Bally Doctor who

This machine came in with two problems, intermittent reboot and the time expander tilts a little bit to the right when it reaches the top position. For the reboot problem I have changed the BR2, C5 and C4. The bridge had already been changed once before and there was a damaged foil connecting the AC to the zero cross detector, the foil was repaired but it didn’t look too nice. I changed the bridge again just to make sure and made a new repair of the foil. But I think the main cause for the reboot problem was the AC connector, J101. I played the game for a couple of days after these repairs and had no reboots at all, so it seems like the first issue is sorted.

The second problem is a bit more troublesome. I have looked at some videos of Dr who at youtube and at several of them the time expander also tilts a bit to the right. So it is either a common fault or a mistake in the design. I need to take out the unit from the playfield to see what’s causing it to tilt.

AMI MM-1 amplifier

A project from the past autumn

 

This is AMI’s first solid state amplifier. It is a stereo amplifier and the electronic design is much like a tube amp, with drive transformers, output transformers and two NPN transistors in each of the output stages. It was completely dead when I got it and it was a quick fix to get it up and running again. It had been in the hands of another repairer who didn’t manage to sort out the problem before I got it. And he had actually found the fault, but made a little mistake when fixing it. The problem was that the 26.5 v supply was missing and the cause was the 27V zener diode, Z1. But when replacing it he turned it the wrong way round and all I had to do was to de solder it and mount it the right way. I played the amplifier for a couple of hours using an MP3 player as signal source. It worked fine and I returned it to the customer again, case closed.

But I got it back again a couple of days later with the complaint that there was way too much background hum in the sound. One disadvantage to have only the amp and not the rest of the machine is that it is hard to be sure everything is OK. I run the amp at the workbench again, and there are some hum in the sound when playing at full volume, but not more than I would expect. I checked the ripple of the +-38 voltage and it was OK.

Since I couldn’t hear any unnatural hum at my workshop I brought it back to the customer and connected it to the box, and there was quite a lot of hum in the sound when playing a record. I also noticed that the volume control had to be turned up quite high to get normal listening level.
We inspected the pick-up together and the stylus didn’t seem to be pushed in to the pick-up properly and the cause turned out to be the wrong stylus in the pick-up. With a proper stylus the pick-up gave a much higher signal and there was no need to turn up the volume control as high as before and the hum was gone. Another thing we found out when inspecting the pick-up was that it was mounted the wrong way round. This sound a bit strange but the tone arm is mounted at the left side of the turntable in this jukebox, at a normal record player the tone arm are to the right instead.

The pick-up has to be turned 180 degrees at the tone arm if it is mounted at the left side of the turn table. Else the stylus might do a pole vault and break while playing a record.  

Star race CPU up and running

I have now got the CPU up and running, but it was a bit tricky. Someone had already been working at the board and socketed the Z11, Z12 and Z13. When measuring the logic levels round these IC’s the levels was far too low, about 2,5-3v and it turned out that the fellow working at it had put back the faulty IC’s in the sockets. After changing these three chips I did still had too low levels at some signals and except for the first three chips I also had to change U4, Z14, Z15, Z34 and Z35. Then it booted properly and the switch matrix worked in the test. But it wasn’t possible to start a game, nothing happened when pressing the start button. I found out that when the ball wasn’t at the outhole switch it was possible to start a game and when dropping the ball back in the outhole everything worked as it should, until it was time to start a new game. The cause for this was the diode at the outhole switch, it was shorted and messed up the switch matrix when it was closed.

It’s still a question mark why all these chips was faulty, I haven’t seen so many broken IC's at the same time before. It might have been caused by an accidental shortage to a higher voltage somewhere at the playfield or something wrong with the 5V supply. The 5V measures Ok now, but I will take the supply board apart to check for any cracked solders or anything else wrong, just to make sure.

Right now I have taken out the playfield to clean up the inserts and go through all the lamps and mechanics at the underside.



 I will replace the battery with an external battery before returning the game

One of the varitargets didn't reset properly and the cause is probably that the solenoid wasn't properly aligned


One slingshot was a bit sluggish when playing the game and this was the cause. The slingshot bracket was broken and the coil stop missing and it was repaired with duct tape. Also the coil sleeve was missing.


Someone seems to have rested the playfield at these lamp holders causing them to get bended. The holders was also loose from the bracket and I had to solder them in place to get them properly grounded.

Gottlieb Star Race

I got a new project in to the workshop during the summer, but there hasn’t been time to start working with it yet. The symptom is that it is booting up but only displaying flickering zeroes at the displays. This is usually related to the slam tilt switch or the switch matrix. I’ll start looking at it during next week.

Star trip delivered

I have finally delivered the Star trip. It was ready to go a month ago, but when powering it up a last time before delivery the CPU was completely dead. I hate when things like that happens, but it was at least good that it happened while the game was still in the workshop.

QA in the reset circuit was bad causing that the reset line went high at the same time as the 5v was applied to the board. This fault was a bit tricky to find, it’s not so easy to measure the short delay of the reset, but after some thinking I realized that the watch dog didn’t reset the CPU as it should and by measuring from the watch dog circuit through the reset circuit I found the faulty transistor. The strange thing is that it measures OK, but after changing it the CPU booted again. I also tried out the CPU board from the second Coney while repairing the Star trip CPU. I wrote earlier that it looked like brand new, but this turned out to be not true. It has had an acid damage but someone had cleaned it up good. When I first tried it it didn’t give any flashes at all, but there was traffic at the address and data bus and this indicates faulty ROM’s. After rebuilding it for EPROM it booted as it should.
    

Another Coney Island

I just bought another Coney Island. And compared with this one my first was in almost excellent condition, well, almost, at least… The good thing with this one is that it still has its CPU and SDU, and even better, some wise guy removed the battery before putting the game in storage. The CPU looks almost like brand new. I haven’t powered it up yet, so I do not know if the ROM IC’s are in working order or not. Other Game Plan CPU’s I have been working on had all faulty ROM’s and had to be rebuilt for EPROM’s. But before I can test the boards I have to assemble the first playfield, I do not want to run the boards against this one. There are also a lot of other useful parts in this game which will be handy to have when assembling the other playfield.

 

The cabinet of this game are really ugly. At some point in time someone has clear coated it and it have become yellowish by the age. It is dented, scratched and pieces of wood are missing. But it is a good candidate for a first try of repainting. Which means that I can keep the old cabinet’s original painting as it is. It’s just like have one's cake and eat it too.

Star Trip completed

The Star Trip is now finally completed and turned out quite god, even if it isn’t the most fun game to play. The playfield are cleaned and polished and got new rubbers and also a new ball since the old one was a bit rusty. The coin rejectors also needed a little adjustment, they didn’t accept modern coins.

Star Trip electronics up and running

I have finally got the electronics to work properly in the Star trip.
The MPU from the Coney Island worked without problems but the SDU, also from the Coney, gave me some problems. When I first started the game, with the playfield connected, the game start tune was played at the solenoids instead of the sound card. The cause turned out to be the MPU connector end of the cable connecting the MPU to the SDU. One address bit was missing, probably due to oxidation in the connector from the battery leakage. Unfortunately I didn’t have this type of connector in stock instead I solved it by soldering the MPU end to the board.
After the first boot with the playfield connected the sound card started to give a continuous beep, also when starting a game and testing some switches some solenoids was pulled instead of the proper beep from the sound card. The cause of this was that the SDU board was modified at several points by interrupted traces and wire jumpers. It looked like someone made a mistake when writing the software addressing the wrong solenoids and instead of correcting the software they modified the board. I removed the wire jumpers and repaired the traces and then most of the game worked as it should. The Coney SDU wasn’t equipped with all driver transistors and the missing ones were used for the sound and one of the slingshots. Five driver transistors later all was working except for the continuous beep from the sound card. One of the jumper wires I had removed from the SDU connected a solenoid to one of the sound card inputs causing the +24 V to be routed to the sound card through the coil causing a capacitor at the input to be shorted. After replacing the capacitor also the sound worked properly.

Some earlier projects

I went through my hard disc and found some pictures of older repair projects.

Bally Corvette
This was a tricky case. Sometimes the LT-5 engine in the top left corner didn’t move as it should. Instead of the smooth movement from side to side and engine like vibrations it just flip flopped from side to side. To find the cause of the problem I had to disassemble the motor unit, which included removing ramps and a lot of playfield parts. The cause of the fault was a bad soldering at the magnetic sensor that feedback the engine movement to the servo circuitry. By the look of the soldering, lack of tin, I suspect that this has been a problem in this machine since it was new.  

While having the playfield disassembled I gave it a good cleaning and polish, it really needed it. The ramp protector for the left side of the LT-5 ramp was missing, so I made a new one and also changed all rubbers. The owner of the game called me after a few days after it had been delivered back complaining that the multiball lock didn’t work as it should. I made a home visit to check the multiball difficulty setting, which was set as liberal, but even though the game acted as the setting was at the hardest level. I changed the setting from liberal to the next level and back to liberal and rebooted the game, and now it worked as it should.

Bally Playboy
This was a fun case and I really enjoyed working with it. The game was in really bad shape, and if it had been some other less valuable model than a Playboy it might had been a case for the scrap bin. There were a lot of faults in the electronics and a few MacGyver solutions, when one fault was repaired another one popped up. Finally I got the electronics working and turned to the playfield and cabinet. The playfield was badly worn, but it had all its original game specific parts. That’s a good thing if someone in the future would like to swap the playfield to a reproduced one. I disassembled the playfield and cleaned and waxed it. I also went through the mechanics at the underside to make sure it worked as it should. The cabinet was cracked in the front corners and someone had tried to repair it with screws and nails. I think I removed about 30 of them to be able to open the corners and glue them together again. Also one of the legbolt bracket was more or less loose in at the inside due to some missing wood.

 

 

Gameplan Sharpshooter
This was a quite straight forward case. The CPU didn't boot due to acid damage from the battery and faulty ROM chips. I cleaned the board, repaired the acid damages and rebuilt it to run from EPROMS. Then the usual disassembly of the playfield, cleaning polishing assembling and new rubbers.
When repairing this game it was the first time I tried out my home built tumbler to polish the metal parts. Maybe not as nice looking a factory built one, but it does work.

 

Star trip first boot

Today the Star trip was booted for the first time. The playfield are still on the workbench, so I couldn’t play the game, but I had the 6 flashes from the LED at the MPU and some beeps from the speaker.  The MPU and SDU boards were missing when I got the game and the boards I used now are from my Coney island project. The Coney has to donate the boards to the Star trip. The plan is then to build a new SDU and use an Arduino Mega to bring the Coney back to life. It will require a lot of programming, which I’m looking forward to.

Hantarex Polo/2

There has been a lot to do at the office the last months so I haven’t had much time to spend with my projects in the workshop…

This weekend I have been repairing a Hantarex Polo monitor from an OK baby cabinet. It had its CRT panel damaged in a transport and somebody else replaced it by a new one but couldn’t get the monitor to work, it just gave a ticking sound when started. After some investigation and surfing for documentation I found out that the monitor was a Polo/2 and the new CRT panel was from a Polo. Electrical they are identical but the connections are marked different between the two and in this case two cables were mixed up causing the 25 V from the PSU to be shorted to ground. After correcting the connections the ticking disappeared and I had glow in the CRT, but no EHT. After some more investigation I found out the deflection yoke was connected to the video input connector instead of to the proper yoke connector. When the yoke connector isn’t connected where it should be there are no power to the LOT driver transformer and no EHT. When connecting the yoke to the proper plug the monitor worked again.

I don’t know how the CRT panel could get so damaged without also damaging the neck of the tube?



Bally Atlantis

I got a new project today, a Bally Atlantis that has been in a nasty accident. It was located in a house which caught fire. Luckily it wasnt in the actual fire but close enough to be badly dammaged. This project will be a real challenge.