I'll do this properly - Floppy drive alignment.
After alot of reading, youtube and trying to understand what the hell Azimuth means to anything I finally have a fully refurbed and correctly aligned SF314 that works a charm. I will try and explain what i did in case others want to try it. TBH once you have all the kit and actually see how they did it back in the day it was actually very simple.
One thing you do need is a proper floppy alignment disk with the necessary 'special' magnetic patterns on the disk (not software). So this is not Atari specific here. I managed to grab one from fleabay for about 20 quid, they do come up often but don't hang around long. The small instruction book that came with it was also helpful to compare against other literature :
Dysan Alignment Disk info.pdf- (3 MiB) Downloaded 53 times
Also some specific Atari related fixing in SAMS Computer Facts - https://docs.dev-docs.org/htm/search.php?find=SAMS
Particularly of interest :
- SAMS facts.png (1.63 MiB) Viewed 3173 times
The video that really helped me understand what was going on and why/what I should be doing was an old Radio Shack employee video on the subject :
https://www.youtube.com/watch?v=BPy4Yf3 ... U&index=48
Ok on with the show.
Oscilloscope connected to the following points on the SF314 control board (pic courtesy of SAMS facts) lets start with Head Radial Alignment check :
- test points.png (748 KiB) Viewed 3173 times
Middle point is GND, either side are you connection points (circled red). Grab you Atari diagnostic cartridge and via the floppy menu send the head out to track 40 (the magic track that has the funky magnetic pattern on it) and if you have the trigger setup correctly on the oscilloscope (as per alignment disk instructions) should show a nice even cats eyes picture, or not in my case :
- 20240218_154527.jpg (234.61 KiB) Viewed 3173 times
As we are just dealing with the bottom head at this point (hard attached to the stepper motor) the adjustment can be done by gently unscrewing the following two screws (in red) and gently moving the motor unit with a flathead screwdriver (blue) :
- adjust lobe.png (132.54 KiB) Viewed 3173 times
Retry the test until the pair of 'lobes' are of equal height, then re-tighten the screws to lock in place.
The azimuth check for the bottom head was also done at this time and after adjusting the setup for the Oscilloscope as per instructions the following happy output was seen :
- 20240218_172348.jpg (232.81 KiB) Viewed 3173 times
This indicates optimal Azimuth alignment too, yay.
Now the difficult bit - the top head!!
As i had been previously just moving the top head by trial and error a few years back I knew this was pretty much out of whack, the problem with the top head in relation to testing and getting results on the oscilloscope is the diagnostic cartridge doesn't enable you to go to track 40 on side 'B' straight away, you have to go to track 40 on side A then select side B, this defeats the trigger as will trigger on index (when the head first moves to track 40) for the life of me I couldn't get the oscilliscope to trigger on anything including side signal. So this is where my phone camera comes in handy as the Oscilliscope was going to fast for me to manually pause it but I could pause and rewind a video of it!
So the head alignment (lobe picture) I could get pretty easily but the Azimuth was always out of whack :
- 20240218_171842.jpg (192.36 KiB) Viewed 3173 times
After alot of trial and error I established that (if looking down on top head with disk slot towards you) moving the head North/South affected the head alignment (lobe) more so and East/West was more the Azimuth setting. After no more than about half hour of small adjustments tightening the two screws at the base of the head as i went then readjusting I finally got near enough perfect :
- 20240218_172348.jpg (232.81 KiB) Viewed 3173 times
Since adjustment its read/written every disk I've thrown at it across multiple ST's, accompanying new PSU (while i gut the old PSU and replace its internals) too and hopefully will have many more years of use as a genuine piece of Atari branded hardware.
If you have any sort of Oscilloscope (doesn't need to be a new storage one as these alignment disks were designed to be used in the 70s/80s using the oscilloscopes of the time) and can get an alignment disk (dysan seem to the THE make but have seen sony ones too) then any drive can be resurrected and personally i think the genuine Atari branded drives should be given more love than the 3rd party one's, if you have one then give it some love its easier than you think.
Hopefully this is not too much of a ramble and the steps can be followed but I will happily answer any questions.
