Hi all:
I hope everyone is having a nice holiday season.
I have retruned to working on an Apple II+ and could use a nudge in the right direction.
This is an Apple II+with an 820-0044-C board.
The machine will not boot from the disk drive. Here are the steps I have take thus far:
- I have removed all cards except the disk controller. -- No change in behavior
- The machine will drop into basic with its ']' prompt after pressing CTRL-RESET
- I have tried a different and known good controller. -- No change
- I have tired couple of known good floppy drives -- No change
Observations:
Drive does the expected and typical clatter when starting (head zeroing? I believe)
Once the clatter is done, drive will spin but never boot from known good Dos 3.3 disk. There is no sound of the head moving.
I suspect chips on the MB but thought I would ask what folks think might help and what chips on the MB I should check.
Thanks all
After I hit send on the original post it dawned on me I never tried booting with only 1 FDD.
Yup, bad drive - I guess. (although I thought it worked on another system)
Can boot with one of the drives. Use only the "bad drive" and no go.
So mystery solved Scooby.
Question now is what is wrong with the bad drive? My guess at first is a bad 74LS125 on the drive's analog board, a classic failure mode, but it could be other things, too, including a dirty hard or improper alignment.
Thanks! That is good to know. I will chekc the chip.
And Merry Christmas!!! :-)
Here are two Monitor commands that bounce signals through the write-protect sense inverter (pin 3) and read-sense inverter (pin11) of the 74LS125. NOTE: These commands test drive 1 attached to a disk controller installed in slot 6.
With disks completely removed from the drive, use CALL-151 to enter the monitor and then enter the following command:
C0ED C0E9 I C0EA C0E8 N C0E3 I C0E2 NThe disk drive should turn on and then off again, and the monitor should print several lines of response bytes, some of which are printed in inverse text. If the inverse bytes are 00 then 00 then 7F, then it indicates that the ULN2003 and 74LS125 appear to be behaving normally. If the cable is bad (or unplugged) then those bytes will all be FF.
This second command resets the controller to sequence-0 and then tries to sense noise through the read amplifier:
C0E9 C0ED I C0EC C0EE C0E8 NBecause the command is listening for noise, it might take more than one try to get an unambiguous response. Likely responses are:
Tell us if you receive a different response that isn't listed -- maybe we can pick it apart and figure out what it means.
DiskII WP tests.png
Thanks! I will definately give this a go over my holiday vacation.