TURBO display problem - resolved

[vernimark]

I didn't check the schematics yet, I had time to run the self test only.
Board seems to work properly but score board shows what you can see in the picture. the 1st image is what I see when the game is in normal operational mode, the rest are pictures of the test mode that had to show 00000 11111 22222 33333 ... 99999 on all lines
THe problem is not on the score board but on the game board because I have another boardset (with ram problems, sprites corrupted) and after some cross check tests I can tell score board is ok.
do you have any experience with this kind of problems?

just to save time

regards,
vernimark

[vernimark]

I had a look to the schematics. as you can see digits don't work properly are all connected to the same buffer. THis buffer goes to pins 33 to 39 of connector 8 on CPU board.
Going to CPU board schematics the back tracking is quite simple. First of all we meet a 75468, a Darlington array. I don't think these darlingtons have problems. Darlingtons are driven by a 74LS48 (IC83) 7 segs driver and it is connected to IC84 that drives all digits.
Problems are on segments and not on digits so I think the problem is the faulty IC83

Tomorrow I'm going to change that IC and I can verify my theory

[Etienne MacGyver]

I love your notebook ! 

[vernimark]

Hehe thank you 

[level42]

Interesting stuff.....I can't help you but I love this stuff Marco !

[vernimark]

YYYYYYESSSSS!

resolved.let go with the next problem....

[Etienne MacGyver]

Nice !