Re: I have a IIgs. So now what?

["Alex Freed" <alexf@mirrow.com>]

"Allen Bong" <allenbsf6502@yahoo.com> wrote in message 
1172886106.223925.122610@31g2000cwt.googlegroups.com">news:1172886106.223925.122610@31g2000cwt.googlegroups.com...

> 74LS14 is a bad substitute for LS06 or LS05 as its o/p are not open-
> collector (see datasheet above)

True.

Looking at the original Apple disk controller it appears that the reason an 
open
collector part was chosen was to drive /RESET and the motor control timer.
Since the chip has 6 inverters it was easier to add resistors for the other 
4 than
use yet another chip.
In case of the /WR REQ signal it doesn't matter much if it's open collector 
or not.

>
>>From my Disk ][ circuit diagram the pullup for the /WR REQ comes from
> the disk drive's analog board.  If you are not getting +5 on pin 4 of
> your 74ls06, it might be an open resistor 1K R15 on the disk drive
> card.

Probably not the case as it's the WRITE that doesn't work and it's active 
low.

>
> Allen
>

-Alex.