AR III board questions

railwarrior

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I have a System 1 cab with the AR III board. Someone had added a switcher and tied into the harness to feed 5vdc in 2 places. Recently, it stopped working in the middle of trying to convert to another sys 1 game. The 10.3v was only putting out about 5vdc so I picked up a rebuild kit from Bob Roberts. R20 already looked burned, so I thought that is why someone hooked up the switcher to provide 5vdc. I 'rebuilt' the AR III. 10.3v now reads 15 vdc. My next step is to replace R20. What's going to keep it from burning up R20 again, if the switcher caused it to burn (or was installed because it was already burned to provide 5vdc)? Is there no 'sense mod' for this board?
 
I'm confused, I thought it was the job of the AR board to make the 5 volts from higher input voltages and send it out.
 
I just replaced R20 and removed the switcher. Now everything works. Anybody know what burns out R20? I have a Paperboy that has a switcher wired into the 5vdc as well.
 
Typically when resistors burn up on the ARII's it's due to bad/flaky edge connectors at the pcb. Make sure they are tight and clean. The pins go bad and cause a lot of resistance which causes the AR to crank up the current and burns up the resistors and edge traces on the pcb.
 
I thought I would check out the game options. When I flipped the test switch on the A/R III board, the screen started rolling.....then the graphics went white and I could make out the marbles still bouncing around. I had to power off the machine and switch back to 'game' for it to come back up correctly.

Now I don't know if I have a problem still with the A/R III or something on the SYS 1 Mobo.
 
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