Need help - setting up old Shugart 800-2 8inch drive on my freedos testbench

[Chuck(G)]

Start with the simple things--is the head making contact with the disk? Sometimes the head-load mech gets messed up and the head doesn't fully descend. This can cause a huge drop in signal amplitude.

 

[_ds_]

Yes I checked the head with the RPM Test in IMD to close the solenoid.

Head must have good contact to disk - see pictures.

open

closed


Strange thing is, I am able to meassrure the INDEX Signal with osci but can not calculate the RPMs within IMD ?!
Could that be a reason that the head is not delivering me a good signal?

 

[Chuck(G)]

Okay, one more time--probably discussed on a different thread recently. IMD does not use the INDEX signal--it wants a formatted, readable disk and computes the time between successive ID reads of the same sector. The NEC 765, unlike the WD 17xx does not make the INDEX signal available to the program application.

What happened to the felt pad on the side opposite the head? It's required for proper operation.

 

[_ds_]

What happened to the felt pad on the side opposite the head? It's required for proper operation.

oh no I lost it - you have eagle eyes.

On the other drive there is this little felt pad.



Where could I get a spare part or how could I fix it on my own? Making an own little felt pad?
btw - I changed the value on the variable resistor R57 because I thought the gain is not good.
Shall I bring the position of the variable resistor to the same level as on my working drive?

 

[Chuck(G)]

After you get the pad in, yes, I'd adjust the level to the recommended spec.
Others may have some ideas about felt "buttons". I've never had to replace one (all of my regular drives are DS). I've long wondered if a billiard cue tip might be suitable, rather than softer felt.
Other folks will have some suggestions, I'm sure.

 

[_ds_]

while cleaning the head with a "cotton bud" and IPA I had an idea ;-)
As a quick and dirty solution, but honestly working, I took a cotton bud and used it as a felt button.



And with this, I am getting RPMs, meassurements in IMD align test and I am able to load a DOS formatted 8" disk and open a textfile
so everything is pretty fine - the potentiometer I adjusted to the same levels as on the other drive which seems to be fine.

IN the next upcomming days I will think about 3d printing this button and adding afterwards some felt onto it.

So finally I have 2 working 8" drives at home both can access the A drive under dos and write data to it - the next big step is to boot from an 8" floppy.
But I think I would need a real dos system and not Freedos or could I also create a boot disk from there?
Since I have a SS,SD floppy and my BIOS assumes a 1.2MB drive, when I create the boot floppy I need to tell the system (similar to sys a that the floppy is half the "wrong" known size.
How to do this?

 

[Chuck(G)]

Single-density; i.e. FM? I thought support for that vanished around PCDOS 2.0. It was never in the BIOS.
Careful with that cotton bud--it'll pick up dirt like crazy, which you don't want.

 

[Andrey_Ak]

The SA800 came in two versions - the uncommon 800-1 with a built in data separator, and the far more common 800-2 without a built in data separator.

Hello!

Can you please tell us in more detail what are the differences between these versions 800-1 and 800-2 ?

I have two drives: an 800-1 with a 25075-1 board and one 800-2 drive with a 25172-0 board. So I can't find any service manual with a schematic diagram of the 25075-1 board.

Drive 800-1 with a 25075-1 board

https://tis.kz/temp/fdd8inch/20250225_203351.jpg

Drive 800-2 with a 25172-0 board

https://tis.kz/temp/fdd8inch/20250225_213235.jpg