(Topic ID: 292764)

AS 2518-35 MPU issue with game Displays


By JethroP

11 days ago

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Topic Stats

  • 12 posts
  • 4 Pinsiders participating
  • Latest reply 9 days ago by northvibe
  • Topic is favorited by 2 Pinsiders

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#1 11 days ago

Have a Star Trek that has display problems related to the MPU, as I swapped out the MPU and the problem went away. I'd like to get the original board fixed.

Symptoms of the bad board. When in attract mode the 4 player displays each show 00. When I press the credit button to start a game the #1 player display goes blank, and the 1's digit on player 3 goes blank. When I play the ball and start scoring points, the #1 display shows the points incrementing, then when the ball drains and the bonus is collected, the digits go blank again until the start of the second ball, except for the 1's and 10's digits. Weird. This continues all throughout the game.

I have ruled out connectors and power supply. I have 170 volts to each display. Everything else on the game seems to work fine (except for some GI lamps out). Any thoughts on what is wrong with the MPU?

#2 11 days ago

My first question is did you repin connectors, but you said just swapping mpu fixed the issue, have you inspected the connector header pins?

Is there any battery acid damage or corrosion?

#3 11 days ago
Quoted from northvibe:

My first question is did you repin connectors, but you said just swapping mpu fixed the issue, have you inspected the connector header pins?
Is there any battery acid damage or corrosion?

I did inspect the header pins (under magnification) and didn't see any cracks. I didn't reflow the solder, as it didn't look necessary. There is no corrosion. Clean board. U10 was an AMI chip and I replaced it as the AMI chips are known to fail, but that didn't make any difference.

#4 11 days ago

Can you upload a video showing all displays and the problem?

Post a clear picture of the MPU board.

#5 10 days ago

I've replaced all the socketed chips with known good chips...well, at least they worked in other boards so I'm calling them good. Uploaded a video to youtube, and really strange now when I started my second player the scoring appears on the credit/ball in play display. Other displays screwed up as shown. Could this possibly be faulty game ROMs?

IMG_9549 (resized).JPG
#6 10 days ago

Are the feature lamps working?

Do me a favor, replace that counterfeit 5101 RAM chip at U8 this time with an old genuine one. I've got a bunch of those with a high failure rate, last one I tested caused the displays to blank out a second after every score change.

#7 9 days ago
Quoted from Quench:

Do me a favor, replace that counterfeit 5101 RAM chip

I did and that solved the problem! Damn counterfeits.
I assumed that since the game booted the 5101 was good. Lesson learned. Thank you.

I have one display where some of the segments glow partially when they should not be lit. See the pic. What would cause this? My HV is adjusted to 170VDC.

IMG_9553 (resized).jpg
#8 9 days ago
Quoted from Quench:

Are the feature lamps working?
Do me a favor, replace that counterfeit 5101 RAM chip at U8 this time with an old genuine one. I've got a bunch of those with a high failure rate, last one I tested caused the displays to blank out a second after scores changed.

Quoted from JethroP:

I did and that solved the problem! Damn counterfeits.
I assumed that since the game booted the 5101 was good. Lesson learned. Thank you.
I have one display where some of the segments glow partially when they should not be lit. See the pic. What would cause this? My HV is adjusted to 170VDC.[quoted image]

WHOAAA greatch catch Quench!! man such a little part that a counter fit breaks the game. Glad this is resolved.

#9 9 days ago
Quoted from JethroP:

I assumed that since the game booted the 5101 was good.

Quoted from northvibe:

WHOAAA greatch catch Quench!! man such a little part that a counter fit breaks the game.


Helps when I experienced something similar. I think the memory cells lose their retention rather quickly, but not quick enough for the boot-up memory test to fail.

Quoted from JethroP:

I have one display where some of the segments glow partially when they should not be lit. See the pic. What would cause this?

Try changing the 4543 decoder chip on the display board. If it doesn't fix it it might be the glass display.

#10 9 days ago
Quoted from northvibe:

Is there any battery acid damage or corrosion?

This is impossible as there is nothing on these boards that has any "acid" inside.

I am guessing you mean "alkaline" damage possibly better stated simply as "battery damage"

#11 9 days ago

Thanks for all the suggestions. It is working now. I replaced the decoder but still had the problem. I cleaned the board with alcohol thinking maybe there was some tracking going on with some black dust on the board. Also reflowed the solder on the end pins (HV and 5V). Not sure what was causing the problem, but it's working as it should now.

#12 9 days ago
Quoted from pins4u:

This is impossible as there is nothing on these boards that has any "acid" inside.
I am guessing you mean "alkaline" damage possibly better stated simply as "battery damage"

Ah ya, alkaline damage is what I meant. Thank you.

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