31 Jan
2024
31 Jan
'24
10:27 p.m.
I believe the pull ups are all on inputs from the external controller
and not for outputs from the drive itself. Looking at the schematic the
Index output (J1-P20) does not go through the pull up resistors.
Thanks again for your help.
On 1/31/2024 3:59 PM, Chuck Guzis via cctalk wrote:
On 1/31/24 13:03, Mike Katz via cctalk wrote:
Michael,
Thank you, that was what I was planning as my next step. I haven't
checked to see if the service manual has a full schematic.
The main purpose of my message on here was to see if I was missing
something obvious like an option trace cut or something like that that I
missed when I checked the manual.
Thanks again,
Mike -
There is indeed a schematic in the 842 service manual PDF page 87 is
what you're looking for. Since the LEDs are always powered, you need
only be concerned with the output of the phototransistor. DMM is fine;
no scope necessary. An opto going bad is not completely unknown on
these drives. (I have a couple of the 842s--good drives, otherwise)
Diskette drives really are non-intelligent devices...
--Chuck