Epson PX-8 specifically TF-10 problem...

[allison]

On 12/09/2017 07:52 PM, Fred Cisin via cctalk wrote:
> On Sat, 9 Dec 2017, allison via cctalk wrote:
>> I have several Epson PX-8s and i used them.. They work well with the
>> various wedges I have.
>> I also Have a PF-10 which is the portable 3.5" 40 track two side floppy.
>> The problem is it randomly does not turn the media unless I give it a
>> push to get it turning.
>> Things checked:
>> * Batteries, NEW fully charge (Both).
>> * internal Power supplies, current voltage and bridged with external
>>    supplies does not help.
>> * media checked for binding, it does not.
>>  When it turns it reads and writes correctly and at the correct speed.
>>  It may do so without help for many tries then will stop required a
>> manual push.
>> At first glance I though there were motor bearing issues but have
>> verified
>> this is not so.   If I force motor on and restrain it I has good torque
>> and no
>> dead spots.  All signals in the motor control look good on the scope.
>> Any thoughts?
>
> How does it detect the presence of a disk?   and/or disk change?
>
>
Functions normally save for the motor does not always turn on command
but will if manually pushed.  All other functions are normal.


>
> Totally irrelevant to the matter at hand:
> BTW, how close to "industry standard" is the interface to the drive
> mechanism itself?   Would it be practical to replace the mechanism
> with one of the 80 track (and also 2 sided?) Epson drives?  Either the
> whole drive, if it is fairly "standard", or just the stepping
> mechanism if there is another Epson drive similar enough?

No its an oddball.  The read-wirite electronics are part of the
intelligent mainboard that communicates
with the pX-8 serially.  The only board that is part of the drive is the
motor control.

Its of the early 80s.   It would be nice to build a replacement with
more storage but the basic design
is a 68B03, 2732 and 765 with read/write amps and filter on that
board.    It would be easier to start
from scratch with an 8085 and a 37c65 but then that would require
figuring out the protocol and
patching the OS (CP/M-80 in Eprom) to accept the larger result.  If I
were to do that I'd do a solidstate
disk using CF or SD.  Its easier to do that using the PX-8 system bus
(parallel data, address and Z80 controls).

> Besides significant increase in capacity, it would simplify data
> interchange a bit.
> Although the track spacing is 67.5 tpi, instead of 135tpi, I wonder
> whether the track width is similarly different.
>

Its not unlike the 5.25" situation with track width as in the the higher
density drives
have narrower heads.  Not unlike Sa450 and FD33GFR.  I can read the
media with
a standard drive by double stepping but to create media I have to first
bulk
erase and then write only every other track or it has a poor error rate.

Allison