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1541 red light constantly on, spindle behaving as expected, drive not responding.

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
262
Location
Finland
Alps mechanics are pretty good, but they too can suffer from misalignment (causing file not found error? when read is attempted).
Your latest drive was modified, right? Check that its mechanics wiring is not modified also.

I always have at least one working drive to test issues (or parts) of the failed drive. It is very helpful when you can rule out say, that the mechanics is guaranteed
to work, because it works with the other pcb. Then I can focus on failed pcb and not chase ghost on trying to repair already working mechanics.

It also works backwards. If the issue is indeed in the mechanics, all of your 6522's could be ok. So, do not throw them away just yet.
 

Hugo Holden

Veteran Member
Joined
Dec 23, 2015
Messages
2,257
Location
Australia
Alps mechanics are pretty good, but they too can suffer from misalignment (causing file not found error? when read is attempted).
Your latest drive was modified, right? Check that its mechanics wiring is not modified also.

I always have at least one working drive to test issues (or parts) of the failed drive. It is very helpful when you can rule out say, that the mechanics is guaranteed
to work, because it works with the other pcb. Then I can focus on failed pcb and not chase ghost on trying to repair already working mechanics.

That is very wise indeed.

This is the same thing I do. I try to have duplicates of parts for complex apparatus. That way if one fails, I can by substitution, find where the problem is .

(Not that I am a "board Jockey"....this was a term coined for people who could not repair pcb's at a component level and would just swap pcb's until the problem went away).

I am more interested in finding the actual fault, and also I subject the failed part to forensic analysis where I can. Then I repair at a pcb level, which I like to do. Quite a good prospect on vintage computer pcb's I have found.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
I had a working drive :D And managed to kill it when rushing, doh.

Has anyone used the book "Commodore 1541 Troubleshooting & Repair Guide", it's far more comprehensive than the Ray Carlson notes - it's suggesting that Q3 may be bad on the latest drive since the measured collector voltage is greater than 1v (around 2.8v).

I've got some transistors on order, they were cheap.

The book is available as a PDF for free online btw.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Well, I'm not sure about that book... I tested the transistor out of circuit and it passed - fitted a new part and no change.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Some progress....

Drive no2 is now working.

The brand new VIA's fixed it.

Drive no 3 still displays 'drive not ready errors'

As do Drive no 1 (which is my original drive that was working)

So, I know I have a working mechanism that I can test those 2 with now.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Although I can load some games & get directories of disks the speed check from the 1541 diag cartridge (which I'm running from my ultimate 1541 II+) shows ERROR. Perhaps there's something else still wrong (although this is with JiffyDOS rom in the drive).
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
OK, so I put a stock ROM in and it's showing 555 speed - I think this must be some bug or other electronics issue as this does not change no matter where I turn the pot to.

Any thoughts?

PS and of course now that I've adjusted the pot nothing is working again.
 
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BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Not sure what's going on, I also tried Zibri's speed test and it's showing a speed of 304.9 no matter where the trim pot is adjusted to - it even shows that value with the U1541 II+ which seems ridiculous.

Head thoroughly scratched.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Does anyone have any ideas how I might be able to set the spindle speed using an oscilloscope to time the target? Would an LDR be sensitive/responsive enough?

I tried using a strobe app on my phone but I think the hardware is limited to less than 50hz as used here in the UK.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
I've not made any progress on these drives, all of the mechanisms seem to be functioning ok (ie motors are working as expected), the drive that I've done the most work on will read directories off drives but fails to successfully load any other files. I've got some LM592's on order as they are the last part of the chain in the 'file not found' scenario. I'll update when they land. A friend is going to lend me a working drive with some disks also just in case I've had some local calamity that has wiped/partially wiped my floppies - but tbh my money is still on the misconnected cables resulting in damaged IC's.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
262
Location
Finland
Glad you got one working! Or at least to read directories.
Perhaps you could try some of these alignment tools:

Some of them have speed testers also. Of course you need to get these to a disc with working drive somehow
and to load to your c64.

I have also floppy image of one disc alighment/speed checker tool that I have had good results. I could
try to get back with it, if you find means to save it to real floppy? It's not with this computer that I'm writing right now though.

The spin speed must be quite accurately spot on, before you are able to read files correctly.
I doubt 304.9 will work, it should not even read the directory. I think beyond about 298...302rpm it gets difficult
and unsure to read floppies.

Sounds strange that turning potentiometer has no effect on spindle rpm. Even slight touch should make big impact.
I wonder if you turned the correct potentiometer.

Any case, wish you good luck in your quest to fix these!
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
592's arrived, replaced them in the drive that I have mostly rechipped and I can now load games - some of the disks that worked previously no longer work, but I think these have been munged by the drive diagnostics. I'll move on to getting the remaining 2 drives fucntional now. Not sure if this is just coincidental and down to the disks that I have been testing - we'll see.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
The speed was at 297 and I've managed to tweak it right onto 300 +- 0.1. This hasn't helped with many of the disks that seem to be failing (which are mainly original copy protected games).

Using the alignment check in the 1541 diag cart, I get 100 on track for every track, but the between track alignment seems to be all over the place, I confess that I don't really know what good looks like there. I can post a screenshot if needed.
 

ClassicHasClass

Veteran Member
Joined
Mar 22, 2013
Messages
1,572
Location
Sunny So Cal
If you feel like a bit of typing, this is a tool I use for testing/attempts at autoalignment. You can see if you get different results with it. Half track alignment is always iffy; many copy protected games fail on even trivially misaligned drives.

Code:
10 print"{r}torquemada 1541{R}"
20 print"this program will mobilize your disk"
30 print"head to its maximum extents using the"
40 print"fdc bump and seek jobs and an alignment"
50 print"master disk you insert. this may help"
55 print"cure sticky heads or alignment errors."
60 print
70 print"{r}warning!!!{R} this program should not be"
80 print"used on functional drives, as it may"
90 print"put them --out-- of alignment! you use"
100 print"this program at your own risk!!!"
110 print
120 print"copyright 2002 cameron kaiser":print"this is at your own risk-ware"
130 input"press return";w$
140 input"{q}device number";dv:ifdv<8ordv>11thenprint"bad device -- bye":end
150 print"checking for device":open15,dv,15:close15:ifst=0goto170
160 print"{r}device"dv"does not appear to exist":end
170 print"checking device signature":open15,dv,15,"ui":input#15,en,em$:close15
180 ifen<>73thenprint"{r}unexpected response code"en"from drive":end
190 dt$=right$(em$,4):ifdt$="1541"goto250
200 ifdt$="1571"goto230
210 a$="not a 1541 or 1571!":b$="this may not work!":gosub5000:ifexthenend
220 goto250
230 a$="this is a 1571!":b$="1571 drives rarely go out of alignment!":gosub5000
240 ifexthenend
250 print"{q}drive and firmware seem operational"
260 print"insert {r}write-protected{R} alignment"
270 print"master into device"dv:poke198,.
280 input"press return when ready";a$
290 open15,dv,15:print#15,"m-r"chr$(0)chr$(28):get#15,a$:a=asc(a$+chr$(0))
300 close15:a=aand16:ifa=0goto320
310 a$="sensor error!":b$="no disk or not write protected!":gosub5000
311 ifexthenend
320 rem *** main loop starts here ***
321 open15,dv,15,"m-w"+chr$(106)+chr$(0)+chr$(1)+chr$(193):input#15,en:close15
322 ifen<>0thenprint"{r}error"en"when changing revcnt":print"check drive ram":end
325 open15,dv,15,"i0":input#15,en,em$,et,es:close15
330 ifen<>0goto342
340 a$="valid track 18 read!":b$="bam seems to be readable now!":gosub5000
341 ifex=1thenprint"{q}resetting ... ";:open15,dv,15,"u:":close15:print"bye":end
342 open15,dv,15,"m-w"+chr$(106)+chr$(0)+chr$(1)+chr$(0):input#15,en:close15
344 ifen<>0thenprint"{r}error"en"when changing revcnt":print"check drive ram":end
345 print"{q}hold space to cancel drive operation"
349 print"{r}doing bump'n'seek ...{]}";
350 open15,dv,15:fory=1to4:printy;
360 t=35:s=0:j=176:gosub5500:ife<>1thenprint"{r}fdc error"e"on seek track 35"
370 t=1:s=0:j=192:gosub5500:ife<>1thenprint"{r}fdc error"e"on bump"
380 t=1:s=0:j=176:gosub5500:ife<>1thenprint"{r}fdc error"e"on seek track 1"
390 ifpeek(198)<>0thenprint:y=999
400 next:close15:print:ify>998thena$="user cancelled!":gosub5000:ifex=1goto341
410 goto320
4999 end
5000 ex=0:print"{r}warning!!!{R} "a$:ifb$<>""thenprintb$:b$=""
5010 poke198,.:input"continue anyway (y/n)";a$:a$=left$(a$,1):ifa$<>"y"thenex=1
5020 return
5500 cy=0
5510 print#15,"m-w"chr$(6)chr$(0)chr$(2)chr$(t)chr$(s)
5520 print#15,"m-w"chr$(0)chr$(0)chr$(1)chr$(j)
5530 cy=cy+1:print#15,"m-r"chr$(0)chr$(0):get#15,a$:e=asc(a$+chr$(0))
5540 ifcy>500thenprint"{r}timeout on fdc job":return
5550 ife>127goto5530
5560 return
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Hey Thanks, I think can copy and paste that via Vice & ftp a d64 to my UII+ I think.

I'll give it a whirl.

BTW, I now also have my original drive 'partially' working again - this was simply the VIA's that were bad.

As in some of the early responses in this thread by VintageVic, I this may actually be issues with my disks (I'm not sure why they would all start to fail when they worked on this drive immediately prior to this escapade), it will read non copy protected disks, a standard floppy with some users files on, and the Commodore Arcade Extravaganzer disk that I have. But I can't get any copy protected disks to work yet.

The other now working drive will boot some of my EA titles, Strike Fleet, Chuck Yeagers AFT.

That original drive is showing a slightly fast spindle sped of 301.5 +- rpm, the half track alignment is showing 100 for most tracks which is different to the other drive which varies from 0 right through to about 90 varying wildly. is a lower number better for half track alignment? Can't think why the copy protected games would load if not?

The third drive I bought (which had the poorly made SpeedDos interface), still refuses to read anything, motors all work, but gives file not founds, and 'ERROR' in a speed check. I replaced the 592's but they were not the issue on this one, rather than pull every chip I'll get the schematics out and do some serious scope work.

It's probably about time that I named these 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

In the photo I posted in earlier the drives from left to right are: DRIVE1, DRIVE3, DRIVE2.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
If you feel like a bit of typing, this is a tool I use for testing/attempts at autoalignment. You can see if you get different results with it. Half track alignment is always iffy; many copy protected games fail on even trivially misaligned drives.

I copy and pasted it over using vice/ftp/uii+, didn't really read it other than to fix some of the errors caused by the substituted control codes, but... it asks for a master alignment disk to be inserted? Is this necessary?

Thanks,

Ben
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
Sorry for lots of posts! I went ahead and tried it with a blank disk on DRIVE 2.

Amazingly, a few more games started to work afterwards.

I'll try this on DRIVE 1 next.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
OK so I've run it on DRIVE 1, and it seemed to get stuck in an endless loop.

It was continually cycling through and alternating the following 2 messages for each attempt:

FDC ERROR 3 ON SEEKING TRACK 35
FDC ERROR 9 ON SEEKING TRACK 1

I've not idea how this is meant to function - did a quick google and only found broken links to the previous version of this forum.

Would appreciate any help - the alignment check using 1541 diag cart on this drive now shows it way off :D

EDIT - ran it again for longer and the alignment came good again, errors went away. The drive will still only load non copy protected disks however. It could just be the age of the titles making them a bit marginal, but this is the drive that they all worked on a couple months back :(It's a real shame as I have some classic originals, Elite, Uridium, Scarabeus, Raid Over Moscow, Leaderboard, etc.
 
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BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
59
DRIVE 3...

Bit of a head scratcher, just won't read anything from the drive - the R/W head resistances are all good. The PCB won't read from the other mechanisms either AND the other mechanism won't read when hooked up to the a good PCB.

Today I replaced the UC2 socket, it was a knarly single wipe one, so I've replaced it with a double wipe one. I also socketed UC1 - and tested that in another drive, it's fine.

Drive just issues 'file not found'.

I'll double check my 592 work.

Alignment check shows all 0's
 
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