(Topic ID: 193108)

EK MPU Issues

By Billc479

4 years ago



Topic Stats

  • 9 posts
  • 4 Pinsiders participating
  • Latest reply 4 years ago by Billc479
  • Topic is favorited by 1 Pinsider

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#1 4 years ago

I am a little baffled by my EK - the boards are original, repinned, and "bulletproofed". The cables connecting to the boards were repinned. , and NVRam installed. When I turn it on, everything goes through the normal sequence - 7 flashes, the displays show zeros, etc., then right after the chimes are done sounding, the displays go blank, and nothing works. All of the power test points on the MPU are rock solid, even during the chimes sounding. This started happening a few days ago - before that, everything was fine.

I'm not sure where to start - Any ideas?

#2 4 years ago

Could there be an issue with the ball trough? Perhaps the machine does not sense there is a ball in the trough.

#3 4 years ago

The ball trough switch works, and the slam switches are open. The scores did not blank when I removed the ball on BOPP and turned it on, so I don't think the ball trough switch is the issue. Thanks for the suggestion.

#4 4 years ago

Will it enter test mode if you push the switch on coin door?

#5 4 years ago

JT - no.

I am beginning to lean toward U11 - looking close, I might have a bad solder joint on the socket. If I get to it today, I'm going to resolder and will report back.

#6 4 years ago

Flakey 5101 ram can cause that kind of issue. So you could have a problem with your NVRam or it's socket.

#7 4 years ago

I replaced U11 socket, followed by a new U11, and the problem did not go away. I will try replacing the RAM socket when I get a chance.

I am assuming a 68B21 is compatible to a 6820. The only difference I saw on the datasheets was the 68B21 could handle some more types of inputs.

#8 4 years ago

Not exactly. A 68B21 is simply at 2 Mhz version of a 6821. I can't remember what changed between the early 20's and the later 21's.

And since the system is only running at around 500-800 KHz, it works fine with either.

#9 4 years ago

Changed the NVRAM socket, still have the same issue. I'm ordering a new NVRam from Pinitech and will try that - maybe I blew up the RAM somehow. I'll post results with the new NVRam when I get them.

I unplugged the door and tried - still the same issue - right after the attract chimes, board goes into the power up state, repeats three or four times, and then no longer does anything. I can turn off power, and the same sequence happens.

I tested the rest of the slam switches, they test OK, so I can eliminate those as causing a reset. Sigh...

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