Going through my latest project, Williams Flash.

Just about ready to move it into the collection from my workspace in the garage and I noticed it is not keeping score properly. I checked each switch individually and they score the proper amount.

I noticed while playing at random times the score will reduce by a large amount like 70 or 80 thousand. Never seen anything like this and its random and not related to any one switch.

has anyone ever seen this before?

Im assuming this must be MPU related, Board was clean when I got it, not battery damage and good sockets (not scanbe) reflowed all pins and new connector on the driver board. Game had some burnt coils and blown transistors on the driver board but that has all been repaired.

pop bumpers seem kind of weak but other than that and the score everything is working as it should.

Any ideas where to start?

All digits display properly in test mode. I have a short video of it happening. Will see if it lets me upload it.

Looks like no video allowed, I took screen shots. Score dropped from 175k to 103K

Screen Shot 2017-08-19 at 4.17.55 PM (resized).png

Screen Shot 2017-08-19 at 4.18.31 PM (resized).png

Passes diagnostics. Both led's flash twice. Display has all segments in test mode.

Loaded the video to youtube, here is the link.

OK, so i figured out it is not actually decrementing the score. It is not showing the number 8 or 9 when adding the score. Testing today just using a switch worth 1000 points it will show 15k,16k,17k,10k,11k and then 20k.

It is adding the score but shows a zero for 8 and a 1 for a 9. In test mode it displays all digits including the 8 and the 9

Does anyone know which section of the MPU would cause this problem?

Has anyone seen this before?

I cannot find any references to it on line

I think I'm going to start by putting a socket on the MPU for the pia and put a new pia in to see what that does for me.

Fortunately IC18 was socketed, so I pulled the 6820 last night. Man it was in there tight, I mean real tight. Put in a new 6821 and then the game would not boot. I have substituted before without issue so either this game does not like it or the new 6821 is bad. The legs on the old 6821 were tarnished so I cleaned them up and put the old chip back in and the problem is gone.

It was warm out when I noticed the problem and kind of cool last night so I need to run it on a warm day to make sure it was not a thermal issue. I will likely put in a new socket this weekend just make sure that was not the problem as well.

Thanks to everyone for their assistance!