1541 disk drive - "File Not Found"

[BennehBoy]

Since I started this thread, I've picked up 2 more 1541's - it's a bad habit

To keep things somewhat easier to follow I'll 'name' the drives:

DRIVE1 - My original 1541, I had upgraded it with a JiffyDos ROM, and fitted a modern DolphinDos interface by bitbreaker4u. Alps mechanism, 1540050 mainboard. No clock circuit bodges, but has the UB1 bodges. Both VIA's replaced with brand new items from Mouser.

DRIVE2 - bought from a well known auction site as 'untested', yeah yeah ALPS mechanism, 1540050 mainboard. clock circuit bodges (cut tracks & some bodge wires around UC5&UC6. factory bodges at UB1. Various failed CMOS chips replaced (UC5, UD1,) both VIA's replaced.

DRIVE3 - bought untested, but saw it had parallel cable, so was hoping for a SpeedDos installation (which it had). SpeedDos adapter was 'falling to bit', I'll remake once the drive is functioning. Alps mechanism, 251830 mainboard. VIA's replaced, 592's replaced. Currently still non functional.

Drive 2 was completely non functioning when I got it. As above I've socketed and and replaced almost every IC on the board during 'fault finding' - whilst I was doing the work on the drive I was cross connecting drive 1's mechanism with it and vice versa. In a stupid rush moment I misaligned some of the internal connectors and ended up with both drives non working. I had managed to fry the VIA's - amazingly brand new ones are still available from Mouser so I bought 6 of them.

VIA's turned up and this got drive 2 working, but Drive 1 still refused to read disks.... Now, somehow, most of the previously working disks have either 'gone bad' (seems unlikely to me - although SWMBO does like to hoover round my gear a lot), OR my 'mucking about' has made the drives more temperamental. Half of the previously working copy protected originals now function in DRIVE 2, and only non copy protected disks work in DRIVE 1. Alignment shouldn't have changed as I've not messed with that - but who knows.

DRIVE 3 arrived when both the above were 'non working' it was a punt to try and get a working drive, but it also showed up with red light of death. The home made SpeedDos adapter in it was erm, very shoddy, and lo and behold it also had a dead VIA (UC3) - replacing this got it to boot, but it steadfastly refuses to read any disks, an alignment check with Jani's 1541 Diag Cart shows 0 readings for every track.... it could be seriously out of alignment but I suspect an electronics issue (the drive head resistance all check out so the head should be OK).

Any ideas anyone? Was specifically hoping @GadgetUK164 might poke his nose in as I know he's repaired a few of these.

[BennehBoy]

I'm not sure if it's just me, but sometimes just getting my thoughts written down results in a flash of inspiration...

I swapped out UC1, the 325572-01 chip that CBM made to condense a lot of the CMOS logic from the long board version of the 1541 to cost reduce the short board version, onw got a working drive!

EDIT, not quite there yet, I can load a directory but no programs. The drive spindle speed is maxing out at 260 (with the adjustment pot fully tweaked), this really needs to be at 300. Could be a voltage issue, or a slipping belt.. although the belt feels tight.

[BennehBoy]

I seem to be having a lot of forehead slapping moments lately - stuff I've forgotten and had to relearn the hard way....

...for example, get the scope on it before making assumptions, buying parts, and wasting time.

A C64C I have ceased communicating via serial during the course of my 1541 repairs. I assumed the CIA had blown, ordered a new pair, fought with the ground plain to extract the chip, socketed the new one, added an ESD protection piggyback (also more cost), put it back together only for it to still not be working.

Turns out the C64C has a 7406 in circuit to help protect from ESD (I don't think the breadbin does?), pulled the 7406 and yeah it had failed. so ~60 quid and a lot of time wasted for a sub quid 74 logic chip.

DOH!

[rubber_jonnie]

I don't know how relevant this is, but I recently repaired an Atari 1050 drive, which is kind of similar in that it has its own processor, RAM, ROM etc.

I was able to treat it like a computer in its own right when I repaired it.

However, I discovered along the way that it has a built in test mode, configured by joining 2 jumpers, that allows you to run it in a specific test mode whilst probing one of the ICs (The FDC) and tuning 3 pots to get the scope readings right.

Maybe the 1541 has something similar that you can use to check it out?

[BennehBoy]

I've managed to get all 3 of the 1541's working. All had various IC failures, but the chief culprit was the VIA chips.

The third drive, has a failing spindle motor, it's required to run at 300 rpm but varied between 170 & 500! Testing the coils, the resistance is low so I figure there's a short in there somewhere. Unfortunately a replacement spindle motor costs about the same as a drive - I'll keep it as a spares unit.

There's no diagnostic mode built into the 1541, but it does offer various flash codes for failure states in which the CPU is able to execute - mine were mainly in states that did not

I've got a diagnostic cartridge that plugs into the C64 (built myself), using the fantastic cartridge rom from here -> http://blog.worldofjani.com/?p=2180 I use this to check the spindle speed, perform a general performance test, and also to do a simple check of the alignment.

One of the working drives has a misaligned stepper, it's 1 track off, so whilst most things work, some games do not. I'll be hooking the scope up to it when I get chance to tune it back in.

I also recently bought one of these -> http://www.go4retro.com/products/zoomfloppy/

When this is coupled with a 1541 which is parallel port enabled (and I have a drive which has DolphinDos 2 installed which includes a parallel port), perfect disk backups can be made at GCR level. I want to do this so I can backup my copy protected originals.

Unfortunately the software required for this doesn't seem to work with my version of DolphinDos (it works with version 3 for 1571 drives), so I'm going to build a speed dos setup in the other drive... one of the drives came with speed dos but the adapter was very Heath Robinson and I'm not going to put that back in:

PXL_20220118_141147523.MP.jpg (203.61 KiB) Viewed 2801 times

Instead I found this really nice openhardware adapter on github -> https://github.com/svenpetersen1965/154 ... r-SpeedDOS

So I've ordered some PCB's from PCBWay.

I'll share some more details when I finally get that up and running.

[BennehBoy]

Forgot I had this photo of the 3 offenders:

PXL_20211126_104356129.jpg (484.92 KiB) Viewed 2800 times

[rubber_jonnie]

Nice work

I have a drive for my Apple ][ (Not apple, Seltron) that won't work and has speed problems. Using Locksmith speed test it bounces between too fast and too slow, occasionally landing on the correct speed (Also had belt slippage), though it is better than it was which was not on the chart at all. I'm going to have to scope it I think, as it only seems to be the speed that is off.

I did watch a vid on Adrians Digital Basement about replacing the power supplies in these with something more modern on account of then running quite warm, is this anything you have thought about?

I'm still mulling, but I don't use my 1541 very much, I tend to use my SD2IEC as the 1541 is so huge!!

[BennehBoy]

They run much warmer in the US on 110v - the FET's have to dissipate more power due to the higher output from the 110v transformer windings.

It would also reduce heat in UK, but I think there are question marks over the ripple introduced by the switching FET replacements that people use (can't see it making that much of a problem on kit of this age, but am happy to be educated).

I had thought it might be the belt too, swapping one in made no difference, and I tried the same mechanism on another PSU in case it was a 12v supply issue - would prefer that it had been as that's easier to fix.

I do use my 1541UII+ a lot, but there's a real sense of nostalgia bout running an original game from floppy

[rubber_jonnie]

They run much warmer in the US on 110v - the FET's have to dissipate more power due to the higher output from the 110v transformer windings.

It would also reduce heat in UK, but I think there are question marks over the ripple introduced by the switching FET replacements that people use (can't see it making that much of a problem on kit of this age, but am happy to be educated).

I had thought it might be the belt too, swapping one in made no difference, and I tried the same mechanism on another PSU in case it was a 12v supply issue - would prefer that it had been as that's easier to fix.

I do use my 1541UII+ a lot, but there's a real sense of nostalgia bout running an original game from floppy

Yeah, I totally get your PoV on the thermals, I might drag mine out and stress test it, see what sort of temp it gets to. One problem I had with the Apple ][ Seltron drive is that the motor spindle was missing a rubber coating round the middle, and as a result the belt was slipping like mad. I managed to fix it ok and get the belt tensioned, but still bad rotational speed. Worried that the control IC is bad, but I guess I need to scope it. Mechanism seems otherwise fine and given it is half height it'd be useful to have working..

[arkadiusz.makarenko]

May I ask what is modern compatible replacement for MOS6522?

I am trying to fixmy 1541, and last thing to test is 6522.

Edit
It is W65C22N... there is even wiki website about it
https://en.m.wikipedia.org/wiki/WDC_65C22