TECH: System 3 boot problem

I have a Rescue 911 that will not boot about every 10th time turning it on. If I turn it off and back on it will usually boot. But it might take 1 or 2 times of doing that. When it doesn't boot the back box lights come on but no other lights. The DMD does not display anything. The LED on the control board and display controller light up and stay light but they should blink. The LED lights on the sound and aux sound boards do not come on.

I have reseated all the connectors. And I tried wiggling them when it doesn't boot but it does not help. I tested voltage for the CPU at P1 connector at pin 1 for +5V and pin 4 for ground. I was able to test it when booting fine and with a boot failure. Both times it tested at +5.08V so I don't think I have a power problem. Any ideas what to check next?

Thanks in advance for your help.

Ken

_{Post edited by kguenther6 : Changed title to get more responces}

I just bought the machine so I don't know how long its done this. Of course I was told every worked 100%

Since I was getting +5.08V I didn't try adjusting it. I'll try bumping it up a bit tonight and see if that helps.

I bumped up the voltage to +5.2V and still have the boot problem. And it seems to be getting more frequent. Any other ideas? Thanks.

Thank you for your replies. I have tried re-seating all the connectors. That didn't help. I'll check out the capacitors tonight and also put the voltage back to 5.1V. Thanks for the suggestions.

Here is an update of what I've done. I have another System 3 pin Mario Andretti. I swapped CPU boards changing out the ROM chips on the swap. Both CPU boards booted fine once swapped and never failed over a number of retries. But the Rescue 911 board that was put into the Mario did not recognise any of the switches for some reason when it was in the Mario. So I switched the boards back. Next thing I tried was to unhook all the the connectors from the CPU board except P1 (power). It booted fine multiple times with no failures. So I plugged in one connector and got a boot failure. I tried another connector and got another boot failure. I tried a few other connectors and I always got a boot failure when booting multiple times. So I tried again without any connectors except power and could never get it to fail. Any suggestions? I would really like to find what is causing the failure instead of just buying a whole new CPU board. Thank you.

Oops. I just read that the DMD board is needed for the CPU to boot. If its not attached then the CPU LED will do a fast flash. It was probably doing that and I mistook it as a successful boot. I'll start my tests over again with the DMD attached. Any suggestions would still be appreciated.

I see the ground modifications were not done on the Rescue 911. I'll do them and see if that helps any.

When it doesn't boot the lights on the back box come on but no lights on the playfield. The DMD does not display anything. It is completely blank. The LEDs on the CPU and DMD driver boards come on and stay on solid. No blinking of the LEDs at all. The LEDs on the sound and auxiliary sound board stay off.

Again, this does not happen every time. It successfully boots 5 out of 6 times.

I'll give that a try and let you know.

Thank you.

An update to my issue. I replaced the U11 chip and so far no boot issue. I was having the problem 1 out of every 4 or 5 boots. But I've booted it about 30 times with no issues so far. Everything I read about U11 problems said the DMD would display garbage but mine didn't display anything. So its a little different than the normal U11 problem. But anyway its working. Thanks to all for your input.

Ken