exxos's Atari, Amiga & retro forum

OK, it seems that I don't have the drive aligned quite right as disks written with the drive can't be read by other drives. Hmm. Another thing which will have to wait until the new year I think.

I'm back from my Dad's in Cornwall and in spite of having to go into work on a Bank Holiday to try to resurrect our core network switch after a flood a couple of floors above went water dripping on the top.

If Aruba hadn't drilled holes in the top of the case the thing would have survived... but...

Anyway, after removing one of the PSUs and the very dead controller board (there are two redundant ones) the unit did start up, but not without the sound of popping MOSFETs deep inside and a smell of burnt component. Thankfully, these aren't needed for what we use it for as I think they were part of the PoE power circuitry on the chassis backplane.

Here's the affected part of the dead manager board.


Despite this I did have a go at realigning the Apricot FP's floppy drive. Unfortunately the drive doesn't output the raw flux to the floppy cable so I couldn't use the oscilloscope to measure things and I just made things worse. It's a right pain as you have to fully disassemble the machine and half the drive to get to the screws holding the stepper motor.

I may get back to this again later in the week.

Mmmm, popping MOSFETs.......

Lashed up a test system for the Apricot FP floppy drive, powering using an ATX power supply and using patch wires into the end of a ribbon cable to bring Motor-On, Head-Load and Drive select low.

There's a convenient output test header on the floppy controller board where you can connect an oscilloscope to monitor the output from the head amplifier circuit. With this I was able to measure the read head output and adjust the stepper motor so that on a floppy written with all bytes being 0xaa on a known good drive I got the largest signal. (I used 0xaa as this is constantly alternating flux and hence was easy to read on the 'scope.)

I'm running test now,

stephen_usher wrote: 04 Jan 2022 20:12 Lashed up a test system for the Apricot FP floppy drive, powering using an ATX power supply and using patch wires into the end of a ribbon cable to bring Motor-On, Head-Load and Drive select low.

There's a convenient output test header on the floppy controller board where you can connect an oscilloscope to monitor the output from the head amplifier circuit. With this I was able to measure the read head output and adjust the stepper motor so that on a floppy written with all bytes being 0xaa on a known good drive I got the largest signal. (I used 0xaa as this is constantly alternating flux and hence was easy to read on the 'scope.)

I'm running test now,

Good luck, hope you can get it adjusted and working. Be interesting so see some pictures of the scope showing good/bad results.

Ah.. Tricky, the machine's all back together again!

Well, the drive is very picky about the floppy drive used to format the disk.

It will read disks written on my STs and TT, and a disk which was written on an Apricot Xi in the distant past, but it doesn't like the ones written on the F2's internal disk or the drive I usually use with my Sinclair QL. It's almost as if the track spacing on those drives is very slightly different and this old drive is more finicky.

You're making me want to start on the Seltron again for the Apple II, there mist be a way of checking the speeds and feedback, just need to figure it out!!

Must finish Mac Classic first!

It helps if you have a circuit diagram and full maintenance documentation, including oscilloscope diagrams, circuit diagrams and schematics for the test system as well (just not the ROM contents or the Sony software and test computer to run it upon).

stephen_usher wrote: 04 Jan 2022 23:12 It helps if you have a circuit diagram and full maintenance documentation, including oscilloscope diagrams, circuit diagrams and schematics for the test system as well (just not the ROM contents or the Sony software and test computer to run it upon).

I have absolutely none of that for the Seltron, seems it's rare as hens teeth!! There is also a possibility that it was designed for a specific disk controller, either Laser or Vtech, but need to do more digging.