RX02 / DSD440 / SA801 problem

From: Tom Leffingwell <tom_at_sba.miami.edu>
Date: Tue Mar 5 20:32:23 2002

On Wed, 6 Mar 2002, Tony Duell wrote:

Good point...I added it to the subject already. :)

> If you're asking about a 'generic' module (drive, PSU, etc) that may
> well have been used in other machines, then post any identification
> that's on that module.

I forgot to get the version off the board last night, and unfortunately I
left it the lab today, so I'll have to get it later. Anyway, it does have
a socketed 40-pin ASIC on it right in the center. The only standard
devices I noticed where some 74xx ones, and an LM339 quad comparator. I
didn't notice any transistors, and I was sort of wondering how the stepper
was driven. I would think that if whatever is driving it is blown, then
it wouldn't move at all.

I had considered swapping the socketed 40-pin IC between the working and
non-working unit, but I don't have proper IC extraction tools, and if its
got really flimsy pins on it, I might screw up my only working unit.
 
> I have schematics for 4 versions of the logic board...
>
> The later ones have a 40 pin ASIC on them. The first worry is that the
> stepper control circuit is mostly inside this ASIC, but the actual motor
> drivers aren't (they're sections of a ULN2047 chip). The older versions
> of the board have the stepper motor circuit built from TTL (which you can
> still get) with discrete power transistors for the motor drivers.
>
> Let me know which version board (or at least if theres a 40 pin chip on
> it, or if there are 3 TO66-can power transistors near one edge) and I
> will see what I can do to help you debug it.
>
> -tony
>
Received on Tue Mar 05 2002 - 20:32:23 GMT