dmemphis
Experienced Member
Got three model IIIs with the same symptom on the test bench: they
fail to give a "Diskette?" prompt.
I don't have a boot floppy here, but I assume it would not work...
First things first... that missing prompt.
Each can power up to Cass? no problem with the BREAK key.
I can write and run BASIC programs.
Conditions are:
power supplies good, cabling good (checked continuity across new variety flex cable,
drives lubricated but operational condition not known.
When powered up, the drive 0 light comes on, heads retracts to rear, but the screen is blank.
BASIC programs can select the drive and move the head back and forth.
INP(240) shows the proper values on and off track 0. (2 & 6)
I've swapped all the boards around always the same result.
I don't have any further diag procedures.
Have failed to find similar failure mode on the web.
Got a solution, ideas, or info?
ie: Does the firmware give up waiting for something before issuing the prompt?
Next step is a Z80 ICE to see what the code is doing- if its crashed or in a loop
unless I get a targeted approach here. But to do anything good, I'd need
an annotated ROM listing...
Odd all three sets of boards do the same thing.
fail to give a "Diskette?" prompt.
I don't have a boot floppy here, but I assume it would not work...
First things first... that missing prompt.
Each can power up to Cass? no problem with the BREAK key.
I can write and run BASIC programs.
Conditions are:
power supplies good, cabling good (checked continuity across new variety flex cable,
drives lubricated but operational condition not known.
When powered up, the drive 0 light comes on, heads retracts to rear, but the screen is blank.
BASIC programs can select the drive and move the head back and forth.
INP(240) shows the proper values on and off track 0. (2 & 6)
I've swapped all the boards around always the same result.
I don't have any further diag procedures.
Have failed to find similar failure mode on the web.
Got a solution, ideas, or info?
ie: Does the firmware give up waiting for something before issuing the prompt?
Next step is a Z80 ICE to see what the code is doing- if its crashed or in a loop
unless I get a targeted approach here. But to do anything good, I'd need
an annotated ROM listing...
Odd all three sets of boards do the same thing.