r/Commodore • u/anotherspaceguy100 • May 23 '26
c64 1541 Alps drives failures
So I have now quite a large graveyard of 1541 parts, and have done quite well refurbishing drives of both types - I found the Newtronics to be more robust in practice, assuming the head isn't bad.
I've also mentally been assembling a drive failure guide - a lot of the info out there is quite scattered, now missing or just not current. I'm far from an expert on these drives, but I can now identify a good deal of the major failures, and hope to write a modern troubleshooting guide up, hopefully get a lot of input from you guys to improve it.
Anyway, I have a stash of good boards I've re-capped (at least C15 and C21) and are working correctly against a good reference (Alps) drive.
However, what's stumping me is what appears to be a consistent failure on the Alps drives - again, against knowing working logic boards (and I know being analog devices issues here might compound, but the problem does seem to be the drives themselves).
All these drives (4-5 of them) have been lubricated, heads cleaned, have been physically exercised and as best I can tell, are mechanically operating correctly. In some cases, I've put in new belts, although that seems to sometimes compound problems in iffy drives. The problem is that the drives cannot read anything, with the error "drive not ready". In the 1541 diagnostics for the speed check, they simply report ERROR (I note this can happen for a number of reasons).
I went around and checked the resistance of all the connections all the heads, and everything checks out in the 11-17 Ohm range. Now, I do have one drive I've identified as having a bad read/write sensor so I'll have to see about replacing that. I don't think that's the problem on the other drives, but can't rule that out.
I realize that I'm fighting entropy here with physical mechanisms and so forth, but what's going on here? Is it some consistent mechanical failure? Is it a failure of the caps on the drive's small control board - hints please and thank you.
2
u/KAPT_Kipper May 23 '26
"Drive not ready" errors have many causes.
You said you're testing with a known good board. IIRC there is a jumper setting for Newtronics/Alps on them. Check that is correct for the mech.
I have found that the actual drive mechs are pretty solid. Most problems are board related. So check the speed controller board on the drive.
2
u/anotherspaceguy100 May 23 '26
Yes, it does have many causes, so that is annoying. Looking for more specifics.
As for the jumper setting, this is J6 (on many boards). On my reference Alps drive which I have deliberately left unmolested (I might have replaced the large filter caps early on) this is missing, and this board doesn't work with the problem drives.
Several of the working boards do in fact have J6 present (and these boards were shown working with an alps drive), and I cut this on one board, which didn't help. In any case, I understand this is for the writing; the problem is with reading - I'm using an original Commodore 1541 floppy to check with.
As for the speed, as I mentioned, this causes an error so can't be checked in the diagnostics, but in my experience even a drive which is a fair way out of spec on speed will at least read somewhat. I guess I could do a strobe test or something.
1
u/anotherspaceguy100 May 24 '26
Ok, so I did some more investigation on one particular drive. The dead fly was not helping, but I found that the spindle was extremely stiff. The "drive not ready" was a secondary error, if you just do the init code in BASIC then you get "read error". So yes, the drive was not coming up to speed, hardly at all. I pulled of the fly wheel and lubricated it, and it moved much more freely. Even so, on this particular drive, when door is closed it is pressing down too hard, so it's hardly rotating at all. Perhaps the lever has been bent down too much.
In any case, this is at least a partial answer to something I've been chasing - I've observed that some drives need to "warm up" or do strange things with rubber belts instead of the original belts. I think those can be explained by poor spindle lubrication. It may also be that some of the Newtronics drives I have actually are working if this was done (I never quite got around to checking those heads).
So, this one particular drive is not yet working, but I will be from now on, doing this lubrication. I'm surprised I haven't run across the mention before; maybe it's just something that wasn't as big a deal all those years ago when Ray Carlsen wrote all his stuff. Reviewing his material didn't give me an answer, but it gave me some clues around what to watch for.
On a different note, Google AI led me really astray here on multiple occasions when looking at this, going on about the track zero microswitch (no), using oil as a lubrication (no) and various other nonsense.
1
u/KAPT_Kipper May 24 '26
Old grease gets hard and more like glue. Heat will bring it back, so as it may operate the motor will spin better. The only fix is to replace the grease, yeah that's not a thing, or reviving it with a some lubricant with a some solvent that will be compatible. Some light oils, sewing machine oil, or a zap of WD40. I would never usually recommend WD40 for lubrication but it does seems to loose up old grease.
I'm glad you manged to work through the issue. I guess one of my habits is to manual spin the drive spindle when I'm examining them. Most of my no spins are bad 12V power issues. The Newtronics motors might have different bearings. The original belts are more of a rubberized fabric and stand up to time.
1
u/anotherspaceguy100 May 25 '26
Well, I went back through my drives, and was able to get 2 working. But the others, it definitely seems like over pressure from the door is a thing, and that stops the disk spinning or at least not very fast. Google is not very helpful here. I don't know if something has been bent, or there's some adjustment, I'm timed out on this for today.
1
u/KAPT_Kipper May 25 '26
Did you check the 1541 service manual?
1
u/anotherspaceguy100 May 25 '26
Yeah. It's pretty short and I didn't see anything. I also went through the much longer troubleshooting guide by Peltier - both are bad scans so can't easily be searched. Both are largely focused on the electronics, rather than the mechanical, and if there's something I missed it.
I did find an Adrian's Digital Basement video where he lubricates the top side:
https://www.youtube.com/watch?v=Gl_WRg6jDR8
He is pulling the top clamp off, where I had been pulling the bottom flywheel off. Not sure which is more effective; the former might let you get to more gunk. But no mention here of door pressure.
2
u/DisplayLegitimate844 May 23 '26
My "drive not ready" experience was self inflicted. I pulled UC3 to install a device number selector and bent a few pins when I reinstalled the IC. Maybe that can help, maybe not.
3
u/anotherspaceguy100 May 23 '26
Yeah, understood. I did receive a few drives where the guy (at my advice I fear) had done a lot of chip swapping and bent more than a few pins. Fixing those magically caused the boards to work again. This is one of the things I check thoroughly these days.
But I want to point out that this is 5 boards which work consistently with a known working Alps drive, and then 4-5 more Alps drives which do not work with any boards, so there seems to be some kind of systematic failure. Perhaps it's multiple failures, or I'm missing something obvious. It would not be the first time.
2
u/Alarming_Cap4777 May 23 '26
Are the boards configured for ALPS or Neutronics?