System 11B display query

[paddythegreek]

A couple of month ago i changed the player 1 display (7 digit alpha numeric) on a mates machine as it had virtually outgassed itself. The new display worked perfect until today when the "F" segment has gone out. The player 2 which is alpha numeric is perfect, so am i right in thinking the 7180 segment drive chip is ok as player 2 is working ok then the fault is actually the new display i installed in player one. The schematic shows the chip driving both player 1 & 2. Thanks Ken

 

[PBrookfield]

Although I've not dealt with an original plasma display unit, I'm getting pretty bloody familiar with System 11 hardware as it's my first machine, I'm a neurotic sort and I will eventually be doing some crazy guff to it.

If the 'F' segment is gone in player 1 but it's okay in player 2 then you are correct, the 7180 is probably OK. I say probably because there's always room for an extremely cryptic and unlikely fault (such as internally the 7180 is incorrectly always going low for player 1's F but not player 2 - stupidly unlikely.)

At this point it is much more likely that it's just the replacement unit that's gone too. As a last hurrah, also check resistor R36 and all traces to U12, but as player 2 is working, the problem is almost certainly the display segment itself.

 

[paddythegreek]

Update: I was out for most of the day but switched m/c on around 4.30 and guess what. The bleedin display is fine.
Left it on for over 2 hrs and still ok..it remains to be seen what happens tomorrow.

 

[PBrookfield]

Update: I was out for most of the day but switched m/c on around 4.30 and guess what. The bleedin display is fine.
Left it on for over 2 hrs and still ok..it remains to be seen what happens tomorrow.

Always fun! Seems to further imply the unit is acting strange, unless the machine was moved - failed resistors and broken traces don't tend to sporadic like that unless moved...

 

[stoptap]

Update: I was out for most of the day but switched m/c on around 4.30 and guess what. The bleedin display is fine.
Left it on for over 2 hrs and still ok..it remains to be seen what happens tomorrow.

Sounds like tarnished connectors. A common issue on older displays. I found they are a lot more robust these displays than I thought they would be. As long as they aren't outgassed then pretty much anything can be repaired on them.