[Techtoolslist] Help troubleshooting a 9010A

[Clay Cowgill]

> Been working on the units and I am finally getting somewhere.

> - I blew U1 on the Display board.  Anyone know what chip this 

> is?  (its the large 40-pin chip)  Marking: P8041A 1210

> 8423

> 535419

> Intel '77

> I confirmed that this was the issue by swapping it out 

> between the displays.


Intel 8041 microcontroller... It's a mask ROM part, IIRC (I think the 8741
was an EPROM version).  It's similar to the 8048, both of which were
predecessors to the ubiquitous 8051... (MCS-51 family vs. the MCS-48 family)

Unless someone has managed to extract the code and you can locate an 8741 to
program it on to, you're probably stuck with just swapping in one from
another unit.

(At some point, maybe getting that particular MCU decapped to preserve the
ROM would be a good idea...)


> Display 2:

> - 10th character sometimes disappears, sometimes is faded, 

> sometimes is fine.  I traced that this is controlled by U4 

> (pin 11) and U8 (pins 2 & 17).  I can replace both, but which 

> is the most likely problem?  Anyone know where I can get U8 

> (UDN6118A) chips?


Allegro and Sprague used to make those...  You could steal some off of an
old Williams pinball VFD driver board, or just type "UDN6118" in on eBay and
there will be some there.

-Clay