RetroHacker
Well-known member
Well, it's been a while. Life got busy, and it was far too cold to do anything in the garage, or move any games out of storage. But, I'm back at it. I spent this entire weekend resurrecting a recent Craigslist find - Robotron. I'll post pictures later. It was a lot of work, but well worth it. Apologies for the long post... you don't have to read it if you don't want to. 
This machine had a lot of major issues, but at least all of the parts were present and accounted for. Ironically, this particular Robotron is in a Joust cabinet - but it's exactly the same style as Robotron! Must have been an early run Joust.
First inspection of the game revealed the sad state it was in. The wood around the bottom edges is splitting, and the lower front right corner is bent in a bit. The upper half of the back door is missing. The power supply isn't connected properly, and there is a second, aftermarket switchmode power supply laying in the bottom of the cabinet, partially connected. The control panel wiring harness is cut off a few inches from the interface board, and it's connector crudely patched onto some twisted pair telephone wire with duct tape - and this phone wire goes up to the control panel, where it is soldered badly to the switches. The control panel has a Robotron overlay, but it was originally a Joust panel - the underside reveals the mount for the Joust stick, the two start buttons have been mounted using the caps from Snapple bottles as washers, and their leaf switches are mounted using bits of plastic silverware as spacers. The joysticks are standard microswitch types - not the proper Wico leaf sticks. Inexplicably, the ground wires from the control panel are connected to the metal brace inside the panel... which isn't connected to anything else.
Examining the original power supply reveals more bad repairs. The rectifier bridge has been replaced with another one with a different pin spacing - and it's attached using inch-long bits of wire, and hovering above the board. The solder joints on the rectifier itself are cold, bad joints, and one is loose completely. One of the fuses has been bypassed with a scrap of wire. The transformer connector must have burned and been damaged - one of the wires is soldred directly to the pin on the board. Further up in the cabinet, the upper interlock switch is held closed by a bent bit of metal - a bit of metal which is touching the spade connector on the back of the switch - better not touch that while the game is plugged in... The previous repairman must have not known that you could just pull the switch _out_. The speaker grille on the front has a hole in it, as does the speaker it's supposed to protect. Why they didn't make those grilles out of metal is beyond me.
Oh, and the filth. The entire inside of the cabinet is coated in it. The monitor is so covered in crud that I can't see the board. This game has never been cleaned. Just wiping the face of the tube with Windex and a paper towel removed a healthy, thick black grime.
First things first, I need to clean this. I started by disassembling the game, removing the metal plates the boards are mounted to, the power distribution block, monitor, control panel, bezel, marquee, everything. Vacuuming and cleaning out the inside of the game make a huge difference. I scrubbed the cabinet inside and out with Murphy's oil soap and water. Then, I tipped the game onto it's back, and propped the base up with a saw horse. This allowed me to squirt wood glue into the delaminating plywood, and clamp it back together. This was able to straighten out the bent corner, and fix the outer layer from seperating any more. Once that was dry, I added aluminum edge channel around the bottom edges. This isn't original, but it hides the rough edge and the bottom edge chips, and prevents it from getting any worse. While I was down here, I replaced a rusted and damaged tee nut for the front right leg leveler. I intended to put all new leg levelers on (it only had two and a half of them when I got it), but the ones I had on hand were too short for this game. I'll have to order some longer ones.
While the glue was drying, I was able to tackle some other things. I cleaned the monitor tube and chassis, and recapped it. The monitor now produces a steady, bright picture. The tube has a fair amount of Robotron screen burn, but it tests good and strong on all three guns, and it's still very clear and bright, so it stays.
Once the cabinet was good, I was able to size up the power supply situation. The original linear supply was badly hacked up, and I really didn't feel like rebuilding it - especially since there was a switchmode supply here already. This switcher is unusual. It looks like a computer supply, but it's a different form factor than the normal AT style. Also, the power cables coming off it are clearly intended for a Wiliams game - there are three connectors, neatly labeled with 'CPU" "ROM" and "SOUND". I disassembled it and cleaned the considerable crud out of it, and cleaned the fan. While I had it on the bench, I hooked it to a dummy load (a car light bulb), and tested it out. All of the voltages were good, and it seemed to be working properly. I verified that the CPU connector has the necessary -5v line for the 4116 DRAM. So, I have a good, working switchmode supply. But how to mount it? It doesn't have any sort of mounting holes or tabs at all, and when I found it, it was just laying in the filth at the bottom of the cabinet. I ended up building a couple of brackets from the leftover aluminum edge channel. One mounts to the front of the supply, using the two lower fan screws to hold it, and the other I screwed into the bottom of the air vents on the other side, using sheet metal screws. And yes, I did check to ensure the screws wouldn't hit anything. I then drilled holes in the brackets, and mounted the new switchmode supply where the original linear regulator board used to mount. It fits absolutely perfectly there, and the cables _just_ reach all the way out to the CPU board. Makes me wonder how this was supposed to be mounted - as it looks like a professionally made replacement supply.
I dusted off the logic boards, and I replaced the battery holder on the CPU board. This game was originally intedned to use three AA batteries to store the high scores and setup information. This has proven to be rather unreliable, due to the poor quality battery holder, but also detrimental, as alkaline batteries are want to leak corrosive gunk all over. Fortunately, the batteries had not leaked yet - but I don't plan on chancing it. I desoldered the old battery holder and fitted a modern coin battery holder for a CR2032. This little lithium battery will last as long (or longer) than the AA's in this application, and it won't leak either.
Next on the agenda was the control panel. The harness that goes from the control panel to the cabinet connector is missing, and the cabinet's harness has been cut up, so I opted to build a new one. Using scrap wire from some other partial/scavenged harness, I built a bundle of wires that plugs into the interface board, and terminates in a 12 position molex connector. Similarly, I rewired the panel, removing that awful mess of phone wire, and fitted that with a mating connector. The harnesses took a long time to make, but it sure looks (and works) much, much nicer than the mess that was there.
Reassembling everything went smoothly. I mounted all the boards back into the cabinet, neatly connected and secured all the wires, double checked everything, crossed my fingers and plugged it in. It lives!
"FACTORY SETTINGS RESTORED". OK, now how do I get off this screen. Pressing ADVANCE inside the coin door does nothing. Hmm. Check the schematic - right - the coin door switches all ground through a seperate connector. One that plugs into the old power supply board. I found the loose connector inside, pulled out the ground wire and grounded it. Power back up, and the switches work. Game comes up nicely, and I can coin up and start a game.
Two things are immediately apparent. I have no sound, and I can't move. I can fire, however. I can fire in all directions. But I can't move. Adjusting the volume control does very little - but if I turn it up all the way, I can just barely hear the game sounds coming through the damaged speaker. First, I tackled the controls. I ruled out the switches and their ground connections by grounding a clip lead and touching it to the wires on the switch terminals. Nothing. The I tried touching it to the back of my new harness connector - in case I had a bad connection on one row of pins. Nothing. I powered down and examined the schematics of the interface board. I can see that all of the switches go through some 4049 CMOS inverting buffers before going to the I/O chip. Looking at the board, I see... an empty socket. Huh? That's supposed to be IC6 - a 4049 - and according to the printset I have, it handles up, down and left for both movement and firing. That doesn't make sense, because all four directions for fire work, and move right doesn't work, even though it's supposed to go through IC5, which is present. But, no matter - schematics aren't always correct, and I know there were a couple different revisions of interface boards. I had a very badly damaged Defender interface board in a pile of junk boards scavenged from a previous warehouse trip, so I dug it out. This board won't work with Robotron, and I don't think it'll work period - it's corroded, bent, and crunched from laying on the floor in a filthy warehouse for years. But, it has the chips I need. The solder was too corroded to melt properly with the iron, so I used a heat gun to heat up the board, and was able to pull the chip out. I plugged the chip into Robotron and powered it back up - and I can move! All the controls work now. I played a quick game. All the sounds are there, but they are extremely quiet.
This machine had a lot of major issues, but at least all of the parts were present and accounted for. Ironically, this particular Robotron is in a Joust cabinet - but it's exactly the same style as Robotron! Must have been an early run Joust.
First inspection of the game revealed the sad state it was in. The wood around the bottom edges is splitting, and the lower front right corner is bent in a bit. The upper half of the back door is missing. The power supply isn't connected properly, and there is a second, aftermarket switchmode power supply laying in the bottom of the cabinet, partially connected. The control panel wiring harness is cut off a few inches from the interface board, and it's connector crudely patched onto some twisted pair telephone wire with duct tape - and this phone wire goes up to the control panel, where it is soldered badly to the switches. The control panel has a Robotron overlay, but it was originally a Joust panel - the underside reveals the mount for the Joust stick, the two start buttons have been mounted using the caps from Snapple bottles as washers, and their leaf switches are mounted using bits of plastic silverware as spacers. The joysticks are standard microswitch types - not the proper Wico leaf sticks. Inexplicably, the ground wires from the control panel are connected to the metal brace inside the panel... which isn't connected to anything else.
Examining the original power supply reveals more bad repairs. The rectifier bridge has been replaced with another one with a different pin spacing - and it's attached using inch-long bits of wire, and hovering above the board. The solder joints on the rectifier itself are cold, bad joints, and one is loose completely. One of the fuses has been bypassed with a scrap of wire. The transformer connector must have burned and been damaged - one of the wires is soldred directly to the pin on the board. Further up in the cabinet, the upper interlock switch is held closed by a bent bit of metal - a bit of metal which is touching the spade connector on the back of the switch - better not touch that while the game is plugged in... The previous repairman must have not known that you could just pull the switch _out_. The speaker grille on the front has a hole in it, as does the speaker it's supposed to protect. Why they didn't make those grilles out of metal is beyond me.
Oh, and the filth. The entire inside of the cabinet is coated in it. The monitor is so covered in crud that I can't see the board. This game has never been cleaned. Just wiping the face of the tube with Windex and a paper towel removed a healthy, thick black grime.
First things first, I need to clean this. I started by disassembling the game, removing the metal plates the boards are mounted to, the power distribution block, monitor, control panel, bezel, marquee, everything. Vacuuming and cleaning out the inside of the game make a huge difference. I scrubbed the cabinet inside and out with Murphy's oil soap and water. Then, I tipped the game onto it's back, and propped the base up with a saw horse. This allowed me to squirt wood glue into the delaminating plywood, and clamp it back together. This was able to straighten out the bent corner, and fix the outer layer from seperating any more. Once that was dry, I added aluminum edge channel around the bottom edges. This isn't original, but it hides the rough edge and the bottom edge chips, and prevents it from getting any worse. While I was down here, I replaced a rusted and damaged tee nut for the front right leg leveler. I intended to put all new leg levelers on (it only had two and a half of them when I got it), but the ones I had on hand were too short for this game. I'll have to order some longer ones.
While the glue was drying, I was able to tackle some other things. I cleaned the monitor tube and chassis, and recapped it. The monitor now produces a steady, bright picture. The tube has a fair amount of Robotron screen burn, but it tests good and strong on all three guns, and it's still very clear and bright, so it stays.
Once the cabinet was good, I was able to size up the power supply situation. The original linear supply was badly hacked up, and I really didn't feel like rebuilding it - especially since there was a switchmode supply here already. This switcher is unusual. It looks like a computer supply, but it's a different form factor than the normal AT style. Also, the power cables coming off it are clearly intended for a Wiliams game - there are three connectors, neatly labeled with 'CPU" "ROM" and "SOUND". I disassembled it and cleaned the considerable crud out of it, and cleaned the fan. While I had it on the bench, I hooked it to a dummy load (a car light bulb), and tested it out. All of the voltages were good, and it seemed to be working properly. I verified that the CPU connector has the necessary -5v line for the 4116 DRAM. So, I have a good, working switchmode supply. But how to mount it? It doesn't have any sort of mounting holes or tabs at all, and when I found it, it was just laying in the filth at the bottom of the cabinet. I ended up building a couple of brackets from the leftover aluminum edge channel. One mounts to the front of the supply, using the two lower fan screws to hold it, and the other I screwed into the bottom of the air vents on the other side, using sheet metal screws. And yes, I did check to ensure the screws wouldn't hit anything. I then drilled holes in the brackets, and mounted the new switchmode supply where the original linear regulator board used to mount. It fits absolutely perfectly there, and the cables _just_ reach all the way out to the CPU board. Makes me wonder how this was supposed to be mounted - as it looks like a professionally made replacement supply.
I dusted off the logic boards, and I replaced the battery holder on the CPU board. This game was originally intedned to use three AA batteries to store the high scores and setup information. This has proven to be rather unreliable, due to the poor quality battery holder, but also detrimental, as alkaline batteries are want to leak corrosive gunk all over. Fortunately, the batteries had not leaked yet - but I don't plan on chancing it. I desoldered the old battery holder and fitted a modern coin battery holder for a CR2032. This little lithium battery will last as long (or longer) than the AA's in this application, and it won't leak either.
Next on the agenda was the control panel. The harness that goes from the control panel to the cabinet connector is missing, and the cabinet's harness has been cut up, so I opted to build a new one. Using scrap wire from some other partial/scavenged harness, I built a bundle of wires that plugs into the interface board, and terminates in a 12 position molex connector. Similarly, I rewired the panel, removing that awful mess of phone wire, and fitted that with a mating connector. The harnesses took a long time to make, but it sure looks (and works) much, much nicer than the mess that was there.
Reassembling everything went smoothly. I mounted all the boards back into the cabinet, neatly connected and secured all the wires, double checked everything, crossed my fingers and plugged it in. It lives!
"FACTORY SETTINGS RESTORED". OK, now how do I get off this screen. Pressing ADVANCE inside the coin door does nothing. Hmm. Check the schematic - right - the coin door switches all ground through a seperate connector. One that plugs into the old power supply board. I found the loose connector inside, pulled out the ground wire and grounded it. Power back up, and the switches work. Game comes up nicely, and I can coin up and start a game.
Two things are immediately apparent. I have no sound, and I can't move. I can fire, however. I can fire in all directions. But I can't move. Adjusting the volume control does very little - but if I turn it up all the way, I can just barely hear the game sounds coming through the damaged speaker. First, I tackled the controls. I ruled out the switches and their ground connections by grounding a clip lead and touching it to the wires on the switch terminals. Nothing. The I tried touching it to the back of my new harness connector - in case I had a bad connection on one row of pins. Nothing. I powered down and examined the schematics of the interface board. I can see that all of the switches go through some 4049 CMOS inverting buffers before going to the I/O chip. Looking at the board, I see... an empty socket. Huh? That's supposed to be IC6 - a 4049 - and according to the printset I have, it handles up, down and left for both movement and firing. That doesn't make sense, because all four directions for fire work, and move right doesn't work, even though it's supposed to go through IC5, which is present. But, no matter - schematics aren't always correct, and I know there were a couple different revisions of interface boards. I had a very badly damaged Defender interface board in a pile of junk boards scavenged from a previous warehouse trip, so I dug it out. This board won't work with Robotron, and I don't think it'll work period - it's corroded, bent, and crunched from laying on the floor in a filthy warehouse for years. But, it has the chips I need. The solder was too corroded to melt properly with the iron, so I used a heat gun to heat up the board, and was able to pull the chip out. I plugged the chip into Robotron and powered it back up - and I can move! All the controls work now. I played a quick game. All the sounds are there, but they are extremely quiet.
