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

[Brent Hilpert]

On 2017-Dec-09, at 6:06 PM, allison via cctalk wrote:
> 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.

How about a problem with the current supply to the motor, such as low gain in the driver.
A progressive failure may be just on the edge of supplying enough current to keep it rotating, but not enough for startup torque.