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
