(Topic ID: 134313)

Space Invaders two flashes on mpu board


By 04barb

3 years ago



Topic Stats

  • 8 posts
  • 5 Pinsiders participating
  • Latest reply 3 years ago by thedefog
  • Topic is favorited by 1 Pinsider

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#1 3 years ago

I had this board working then about 6 months ago I replaced the 5101 ram chip and socket. Now I'm back to two blinks again. This board has corrosion and I did the vinegar/water trick, but since then I have gotten a bead blaster. I don't think the 5011 ram chip just went bad by itself. I dread removing the socket because I had to stitch 2 or 3 traces, as I recall. Is there something else besides the corrosion coming back that would destroy 5101 ram chips?

#2 3 years ago

Let's see a pic of the corrosion around the RAM to the ground plane.

#3 3 years ago

Okay, I will snap a picture. I replaced the 5101 ram with a new one and still only two blinks.

#4 3 years ago

I think I found this on the internet somewhere. Hope it helps:

Continuity Chart for U8 5101 RAM in a Bally AS2518-17, -35 or Stern MPU-100 Board

IC & Pin# Data Address Continuity Points

U8 pin 1 (A3) U7 pin 20, U6 pin 5, U9 pin 12

U8 pin 2 (A2) U7 pin 21, U6 pin 6, U9 pin 11

U8 pin 3 (A1) U7 pin 22, U6 pin 7, U9 pin 10, U11 pin 35

U8 pin 4 (A0) U7 pin 23, U6 pin 8, U9 pin 9, U11 pin 36

U8 pin 5 (A5) U7 pin 18, U6 pin 3, U9 pin 14

U8 pin 6 (A6) U7 pin 17, U6 pin 2, U9 pin 15

U8 pin 7 (A7) U7 pin 15, U6 pin 1, U9 pin 16, U11 pin 24

U8 pin 8 GROUND

U8 pins 9&10 (D10&D00) U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (* pins 9 & 10 siamesed together)

U8 pins 11&12 (D11&D01) U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (* pins 11 & 12 siamesed together)

U8 pins 13&14 (D12& D02) U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 &14 siamesed together)

U8 pins 15&16 (D13&D03) U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (* pins 15&16 siamesed together)

U8 pin 17 (CE2) Q5 Right Upper leg, U9 pin 40, U11 pin 34

U8 pin 18 (OD) U18 pin 6

U8 pin 19 (CE1) U17 pin 8

U8 pin 20 (R/W) U7 pin 16, U9 pin 34, U11 pin 21, U18 pin 7

U8 pin 21 (A4) U7 pin 19, U6 pin 4, U11 pin 22

U8 pin 22 (Vcc) C13 Left Leg, R12 upper Leg, CR5 Lower Leg

#5 3 years ago

IMG_20150728_090711.jpg

IMG_20150728_090702.jpg

IMG_20150728_090645.jpg

#6 3 years ago

Pictures

#7 3 years ago

5101 is a sensitive little guy, static is not his friend.

#8 3 years ago

I'd replace some of those components. Those solder joints aren't so nice. Remove & clean up those pads and put some new components in CR7, C80, R12, C13, and anything else that looks like those. Otherwise you could be going in circles trying to figure it out. I've had the best long-term luck with corrosion repair when I just clean and repopulate entire affected areas. You may wanna take a fiber pen to the pads after cleaning them out. Good luck!

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