1581 Followup: Let's get this thing working! (and figure out why it isn't)

[@networkg]

Your step by step approach and attention to detail is your brilliance. I just might have a go at making one of these for myself. Thank you for such an informative video.

[@TimsRetroCorner]

Thanks, I think the perseverance paid off in the end. Good luck with your build if you decide to go for it.

[@daisywong-ke1kz]

Really COOL work!🤩

[@tommyovesen]

Great video and research! Thanks!

[@bwack]

I was home ill today, had some time watching. I enjoyed it :) 1:14:30 - when drive 1 does not detect disk change, I noticed that it randomly turns on the motor when the disk is out.Bad contacts in the disk-detect switch ? Maybe a bit of contact cleaner will help.

[@TimsRetroCorner]

Thanks, I'll give that a go. I'm hoping to do a long term follow up at some time in the distant(!) future, which will include drive maintenance required. This was just a "quick" test, and didn't really dig into drive mech problems (it was way long as it was!)

[@TLang-el6sk]

As I mentioned in a comment to your last 1581 replica video I had some trouble with bad switches in these SFD-321B drives. I noticed that the one of your drives having problems with the disk change randomly started the motor - this could be related to faulty switches. I also think that the adapter PCB is not a replacement for a proper conversion: None of the two circuits you have shown creates a proper timing for the ready signal. In one case it's just synchronized to the index pulse, but that doesn't guarantee the drive is up to speed and stable. The index pulse can arrive from nearly 0 rotations to 1 rotation after the motor has turned on and the drive selected. The other circuit does no timing/synchronization at all.

[@TimsRetroCorner]

Others have mentioned the switch in that drive - it's definitely worth looking into 👍

[@TLang-el6sk]

@@TimsRetroCorner Yes, for sure. With one of my drives the switch was on the edge of failing. And: Take care with newer revisions of these drives. I also mentioned this before - there are HD only revisions where the HD selection switch is missing completely and the drive is configured for HD only! I rewired the one of my drives with this limitation to DD only as I planned to use it in an Amiga or 1581 only. I hope your odyssey ends without killing many more rare and expensive chips...

[@SteveGuidi]

I recently got to the bottom of my 1581 issue, but it wasn't as complex as yours. In the end, my DIY 1581 with the Sony MPF920 was working all along. The main issue was that my C16 uses a 6502-based CPU with adaptor circuitry, and that I was testing with JiffyDOS. There is nothing wrong with JiffyDOS, but the CPU adapter frustratingly doesn't work with it (confirmed via other users of the same board). Once I switched to using the stock kernal, all directory and SEQ file load corruption/hangs ceased.

[@TimsRetroCorner]

That's worth knowing. I have a 6510 with adapter in my Plus/4, and some 6502 adapters waiting to go into some other repairs. BTW, did you need the stock kernel in the 1581 as well as the C16?

[@SteveGuidi]

@@TimsRetroCornerEither ROM in the drive worked during my testing, regardless of how the CPU kernal is configured. I generally leave the drive in JiffyDOS mode and don't experience any issues. I have the same 6510 adapter, but I haven't tested it with the 1581 yet. I'm confident it will work as there is no modified JiffyDOS kernal ROM that supports the 6510 adapter board (yet?). For reference, I'm using the "Monotech MOS CPU Replacer" board.

[@CaptainCommodore]

Well done chap, great perseverance although I may be a little wary of those brick type psus for the 1581 as there's no filtering or reservoir, bung a load on it and scope that bad boy and see it is rippling its tits off.......

[@borayurt66]

Comprehensive video, thank you. I have a couple of PC drives sitting and doing nothing. I would like to use one of them as an external (DF1) drive for my A500+, can you please give the github link to that converter PCB you built?

[@TimsRetroCorner]

This is the adapter that I built in this video github.com/gianlucarenzi/AmigaPCDriveAdapter I'll also update the description.

[@TinySmall69]

Hi, for the white board: does it matter that you have .. - a WD1770 and the Jumper J1 is shorted, - the 6526 seems not to be a 6526-A version, because the 1581 is running at 2MHz ? What would mean if J1 is wrongly set the disk timing parameters are wrong, and the 6526 not having a predictable behavior at 2MHz ! @54:38 Edit: also the technical specification of a 8520 and a 6526 are slightly different, even they are almost the same, one of them has pull-ups on the ports where the other doesn't, and the other way round!

[@TimsRetroCorner]

The only difference is in the head step speed. The 1581 doesn't use the faster speeds of the WD1772, so J1 will switch between the same two speeds regardless of which chip is used. In practice, leaving J1 open will just change the step rate from 6ms to 12ms, and make the drive slower seeking between tracks. The 6526 seems fine at 2MHz. The only thing that I think really depends on the phi-2 clock though is the shift register, which runs fast serial mode. In off camera testing, fast mode was sending data at 4s for a 15k file (vs 38secs in slow mode), and was consistent between the grey & white drives.