My Robotron blew a fuse (F5 7ASB) a few weeks ago; first problem it's had in over a year. I replaced the fuse, checked the voltage. Ran it for a few more hours; everything seemed good.
A few weeks later, it starts resetting sporadically; every 20 to 30 minutes, then gradually gets more frequent, until it blew the fuse again. I checked everything out again, installed the 5V adjustment pot to fine tune the voltage. I'm getting about 5.05v to the CPU. I also reflowed the headers on the CPU PCB and P/S board. It seemed to run fine for a while, then started up again.
It blew the fuse again, and I did a little more research. Someone suggested a seemingly unrelated issue which supposedly fixed his Robotron, doing the same thing, so I tried disconnecting the coin lock coils. No change.
Voltages are all good. I powered it up and checked temperatures. The F5 fuse quickly rises up to about 190 degrees. Resistor R3 gets really hot; around 200 degrees. I don't really see any heat issues on the CPU PCB, except the CPU. The 6809E is getting up to about 120, which I think is a little hot.
Other than the resetting and the lines on the screen, which I believe are unrelated, the game plays great; nothing that would suggest any other problems.
I'm down to my last 7A fuse, so I'd like to fix this fairly quickly.
Should R3 get really hot? If not, does this indicate a bad resistor, or something else in the circuit causing it to overheat.
Should the CPU heat up to over 120 degrees? If not, same question as the resistor.
Thanks!
A few weeks later, it starts resetting sporadically; every 20 to 30 minutes, then gradually gets more frequent, until it blew the fuse again. I checked everything out again, installed the 5V adjustment pot to fine tune the voltage. I'm getting about 5.05v to the CPU. I also reflowed the headers on the CPU PCB and P/S board. It seemed to run fine for a while, then started up again.
It blew the fuse again, and I did a little more research. Someone suggested a seemingly unrelated issue which supposedly fixed his Robotron, doing the same thing, so I tried disconnecting the coin lock coils. No change.
Voltages are all good. I powered it up and checked temperatures. The F5 fuse quickly rises up to about 190 degrees. Resistor R3 gets really hot; around 200 degrees. I don't really see any heat issues on the CPU PCB, except the CPU. The 6809E is getting up to about 120, which I think is a little hot.
Other than the resetting and the lines on the screen, which I believe are unrelated, the game plays great; nothing that would suggest any other problems.
I'm down to my last 7A fuse, so I'd like to fix this fairly quickly.
Should R3 get really hot? If not, does this indicate a bad resistor, or something else in the circuit causing it to overheat.
Should the CPU heat up to over 120 degrees? If not, same question as the resistor.
Thanks!

