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Model III disk drive - no "Diskette?" prompt

dmemphis

dmemphis

Experienced Member
Joined
Oct 4, 2014
Messages
262
Location
Pottstown, PA
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.
 
Progress: Having success with an HxC2001.
I'm using the same cables as with the real drive.
Adapted the HxC to fit the original old floppy cable.
Booting LDOS now at will off that.
Took a while to get oriented to it and loaded with LDOS.
So I guess my physical drives are ALL bad?
Same failure mode on them all?
Ideas to diagnose them?
Or might HxC be masking something...
 
If the Drives are stepping back to Track 0, I'd check the Track 0 Signal and
also the Index Pulse signals to the Floppy Disk Controller. If the Floppy
can't be read you should be getting the Diskette? Message telling you that
you should insert a Bootable Floppy.

You can also Verfiy that you are getting the READ and WRITE Signals to the FDC.

Larry
 
Last edited:
I don't have a boot floppy here, but I assume it would not work...
First things first... that missing prompt.
Click to expand...

The only time you're going to see "Diskette?" is if you have a disk in the drive WITH THE DOOR OPEN.

Turn it on with no disk in the drive and you'll have a blank screen and Diskette? will never appear.
 
You are right, just put a diskette in a physical drive and got the prompt.
Wow. A major misunderstanding on my part.
Best I can say that was a bad user interface design...
Diskette? would have been good to present without a diskette in the drive too.
(Leading me to assume that was how it behaved)
It was nagging me that someone this was operator error since all three machines
did it but I didn't make the connection between diskette in or out.
The good news, is maybe most of the drives work this project will be successful...
So, yes to one of my questions, is the machine waiting for something to give
the prompt... yes... me. Argh!
 
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