(Topic ID: 120799)

DE Simpsons display issue - segment stuck on


By bestofthebunch

5 years ago



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  • 11 posts
  • 3 Pinsiders participating
  • Latest reply 5 years ago by barakandl
  • No one calls this topic a favorite

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#1 5 years ago

I have a Simpsons and the centre segment is stuck on on both display tubes, any idea where I should look?

#2 5 years ago

Could be a few things.
Connector
Resistor SIP
6821 at position 9B

Which segment is it?
Do you have a logic probe?

DE display segment letters
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#3 5 years ago

It's "G" I changed PIA and still stuck on, yes have a logic probe

Cheers
Brian

#4 5 years ago

Strange...since the G segment is driven by separate logic on each tube, which would seem to require two separate failures.

http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Alphanumeric_Issues

--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#5 5 years ago

I have a Rottendog MPU and just realised the dip settings are set on Williams I'm hoping this is the issue so I'll check when I get home and change the settings. Not sure if this would cause it?

Cheers
Brian

#6 5 years ago

Ok just looked again, top display "G" is stuck on, bottom display "M" is stuck on. The dip switches made no difference, hope that will help to point me where to look

Cheers
Brian

#7 5 years ago

Have ordered a new display but any help to fix this as a spare would be great

Cheers
Brian

#8 5 years ago

Well...with a RD board in there...I'm out of the game.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://ww.PinWiki.com - The Place to go for Pinball Repair Info

#9 5 years ago

New display board in and it's all working perfectly so just need to know what to look at on old board to fix it

Cheers
Brian

#10 5 years ago

I had considered that, but the circuitry on the board =should= have separate enables for that segment. i.e...there are different ICs responsible for segment G on the upper glass and on the lower glass.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#11 5 years ago
Quoted from bestofthebunch:

New display board in and it's all working perfectly so just need to know what to look at on old board to fix it
Cheers
Brian

Follow the segment drive. Check the decoder output and compare to other segments. If the decoder is working, it is probably the UDN chip. Don't touch the probe to the -100v side of the circuit. Just the 5v logic level side. You can use your DMM to get a good idea if the HV driver is working. Just compare average voltages. if it is stuck at -100, then that is the problem if the decoder output is good.

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