I am the proud owner of great looking Space Riders. This is my first Atari project and would welcome any advice on where best to start troubleshooting.

The game actually turns on but does crazy stuff each time I turn it on. It sometimes fires all coils repeatedly, the displays show random 0's scrolling across the players, and it has some garbled sound. Other times, some of the coils will lock on and the displays show all 0s correctly. I take all this as a decent sign that the boards still have life in them but not sure where to start. I will download the schematics and start trying to understand this pin.

Should be a fun project!

Hey Ken,

Thanks for the link. I have made a little progress. I cleaned the roms and and the 40 pin IC and the coils no longer continuously fire. Now all lights on the pf blink and the score displays and credit/ball in play displays all blink 0s. The auxiliary board beeps in unison with the blinking lights.

It occurred to me that it could be the voltages causing the pin to constantly flash lights at power up. What is the best way to test the VAC from the power supply for the logic bus? Should be 10 vac going through fuse 2. I don't see any test points. Strange design with everything including the transformers all connected to one piece of metal.

I decided to replace the rectifiers and capacitors on the power supply and rebuild the power circuit on the mpu board as well - replaced lm323 and the capacitor and resistor. I am still not getting 5vdc on the mpu board.

MPU power supply connector pin 1 at J9 should show 10 volts. It is showing 1.61 volts. Checking VAC voltage across the each fuse on the fuse block registers very low voltage on some fuses and no voltage on other fuses. The ceramic resistor on the MPU also gets too hot to touch.

Is this indicating a transformer issue? A short?

Thanks, this atari pin is all new to me.

I pulled the transformer/power supply unit and checked for continuity across the entire power supply. Everything checked out okay. I double checked the new rectifiers and connections - all is okay. I reinstalled the transformer/power supply unit and checked continuity from the power supply to the MPU board connection and power supply to the auxiliary board- all connections buzz as they should.

Turn the power on, and no volts to the mpu or auxiliary board. No volts coming off the rectifiers or capacitors.

I do have 117volts to the bg cabinet and those lights work. This connection does not go through the transformer.

Is it the transformer? I don't see an easy way to check voltage off the transformer - wire connect underneath it. Transformers seldom go bad so that would be odd.

I got my hands on a known working power supply. I still do not show 5vdc on the power section of the MPU. Where is the proper place to ground on these pins to check VDC since there is not a ground strap or braid?

Basically still the same issues. GI lights flash when powered on and displays and credit/ball in play flash all "0s".

Any advice would be greatly appreciated. PF has cleaned up really nice if I can get the darn thing working.

With the power supply disconnected from the MPU and auxiliary board, on bridge rectifier 2 - controls 5vdc logic power supply - I measure 10.8 vac on the blue and violet/blue wires. That is the correct reading. The vdc on the same rectifier which is orange/blue and yellow/black measures .15vdc. The bridge rectifier is good. On the other two rectifiers which are also good I measure correct VAC, but again no VDC. I am getting these measures with a known good power supply.

Since there is no ground strap or braid I am grounding to the cabinet hardware to test VDC.

Damn thing is a mystery.

I decided to check for voltage at the proms top left of the PCB. Both are showing 4.95 vdc. I must be measuring something wrong off the power supply. There is no voltage at the main MPU IC in the center left of the board.