Two 1541-II drives with problems

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Two 1541-II drives with problems

Ville Laustela

Hello!

I found out that I own two Commodore 1541-II disk drives, both in a non-working state.

Testing with a measured-good PSU, I got the following results with both drives:

- power on: normal activity (power led on, spindle runs and drive led lights for few seconds, then stop)
- connected to a C64: drive resets with the computer normally
- attempting to load halts at "SEARCHING FOR": drive spins (with leds on) but the stepper doesn't move. Only way out is to reset the computer.

By the Ray Carlsen's website (http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt) these symptoms point to either U7 logic chip (7406) or U6 VIA (6522). On one of the two drives I replaced the U7 chip but that had no effect.

Before I start a (lenghty, painful, boring...) removal of the 6522 VIA, I would like to ask here if anyone would have any other ideas?

Cheers,
Ville


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Re: Two 1541-II drives with problems

William Levak


Sometimes on these drives, if the head is too far out, when you reset the
drive, it does not find the directory, and therefore cannot read a file.

There are only two ways to fix this:

    1) issue a block read command to track 1.
    2) open up the drive and physically move the head all the way in.

This is worth doing before attempting electrical repairs.

On Sat, 19 Apr 2014, Ville Laustela wrote:

>
> Hello!
>
> I found out that I own two Commodore 1541-II disk drives, both in a non-working state.
>
> Testing with a measured-good PSU, I got the following results with both drives:
>
> - power on: normal activity (power led on, spindle runs and drive led lights for few seconds, then stop)
> - connected to a C64: drive resets with the computer normally
> - attempting to load halts at "SEARCHING FOR": drive spins (with leds on) but the stepper doesn't move. Only way out is to reset the computer.
>
> By the Ray Carlsen's website (http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt) these symptoms point to either U7 logic chip (7406) or U6 VIA (6522). On one of the two drives I replaced the U7 chip but that had no effect.
>
> Before I start a (lenghty, painful, boring...) removal of the 6522 VIA, I would like to ask here if anyone would have any other ideas?
>
> Cheers,
> Ville
>
>
>       Message was sent through the cbm-hackers mailing list
>
>

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Re: Two 1541-II drives with problems

silverdr-2
The easiest way to recover from the head being positioned above usable track range is to issue an explicit initialization command "I". But I wouldn't expect this to be the case here. Judging by the symptoms (system hanging when the communication is about to happen rather than drive trying to move the head a few times and returning an error) I'd rather expect one of the return lines being fried. What I'd do would be to tap on the lines with a scope or LA and check what's happening there. Both before and after the 06 inverter. This should lead me to the suspect (which probably is one of the mentioned ICs anyway). But I am not sure if the OP has the required equipment at hand.

On 20 April 2014 06:30:33 CEST, William Levak <[hidden email]> wrote:


Sometimes on these drives, if the head is too far out, when you reset the
drive, it does not find the directory, and therefore cannot read a file.

There are only two ways to fix this:

1) issue a block read command to track 1.
2) open up the drive and physically move the head all the way in.

This is worth doing before attempting electrical repairs.

On Sat, 19 Apr 2014, Ville Laustela wrote:


Hello!

I found out that I own two Commodore 1541-II disk drives, both in a non-working state.

Testing with a measured-good PSU, I got the following results with both drives:

- power on: normal activity (power led on, spindle runs and drive led lights for few seconds, then stop)
- connected to a C64: drive resets with the c omputer normally
- attempting to load halts at "SEARCHING FOR": drive spins (with leds on) but the stepper doesn't move. Only way out is to reset the computer.

By the Ray Carlsen's website (http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt) these symptoms point to either U7 logic chip (7406) or U6 VIA (6522). On one of the two drives I replaced the U7 chip but that had no effect.

Before I start a (lenghty, painful, boring...) removal of the 6522 VIA, I would like to ask here if anyone would have any other ideas?

Cheers,
Ville


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Re: Two 1541-II drives with problems

silverdr-2
In reply to this post by Ville Laustela


On 19 April 2014 14:14:23 CEST, Ville Laustela <[hidden email]> wrote:

>- power on: normal activity (power led on, spindle runs and drive led
>lights for few seconds, then stop)

That's good. Means that it found no internal problems. The worst usually is when the led remains on all the time

>- connected to a C64: drive resets with the computer normally

You mean when you power the computer on? There goes a RESET line along the cable. If the drive passes its POST at power up, you can quite safely bet that it will pass the reset correctly as well. At least I haven't seen a single case that would not.

>- attempting to load halts at "SEARCHING FOR": drive spins (with leds
>on) but the stepper doesn't move. Only way out is to reset the
>computer.

Which tells us that the communication from the computer to the drive works more or less fine (drive received expected commands and tries to deliver results). The problem looks like the communication back doesn't work. This would indeed point to the ICs mentioned below.

>
>By the Ray Carlsen's website
>(http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt)
>these symptoms point to either U7 logic chip (7406) or U6 VIA (6522).
>On one of the two drives I replaced the U7 chip but that had no effect.
>
>Before I start a (lenghty, painful, boring...) removal of the 6522 VIA,
>I would like to ask here if anyone would have any other ideas?

If you have a way to check the serial lines with a scope that should shed more light. But.. manage your expectations and be prepared for the boring job anyway. While one can never be 100% sure, odds are good that new VIA is your friend there.

-- 
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Re: Two 1541-II drives with problems

Greg King-3
In reply to this post by William Levak
There's an easier way:
    3) Initiate the disk.

But, that condition jiggles the head (moves the stepper motor), and doesn't
jam the computer; so, it isn't his problem.

-----Original Message-----
From: William Levak
Sent: Sunday, April 20, 2014; 12:30 AM -0400

Sometimes on these drives, if the head is too far out, when you reset the
drive, it does not find the directory, and therefore cannot read a file.

There are only two ways to fix this:
    1) issue a block-read command to track 1.
    2) open up the drive, and physically move the head all the way in.

This is worth doing before attempting electrical repairs.

On Sat, 19 Apr 2014, Ville Laustela wrote:

>
> I found out that I own two Commodore 1541-II disk drives, both in a
> non-working state.
>
> Testing with a measured-good PSU, I got the following results with both
> drives:
>
> - power on: normal activity (power led on, spindle runs, and drive led
> lights for a few seconds, then stops)
> - connected to a C64: drive resets with the computer normally
> - attempting to load halts at "SEARCHING FOR": drive spins (with leds on);
> but, the stepper doesn't move. Only way out is to reset the computer.
>
> By the Ray Carlsen's website
> (http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt),
> those symptoms point to either U7 logic chip (7406) or U6 VIA (6522). On
> one of the two drives, I replaced the U7 chip; but, that had no effect.
>
> Before I start a (lengthy, painful, boring...) removal of the 6522 VIA, I
> would like to ask here if anyone would have any other ideas?
>
> Cheers, Ville


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Re: Two 1541-II drives with problems

Gerrit Heitsch
In reply to this post by Ville Laustela
On 04/19/2014 02:14 PM, Ville Laustela wrote:

>
> Hello!
>
> I found out that I own two Commodore 1541-II disk drives, both in a non-working state.
>
> Testing with a measured-good PSU, I got the following results with both drives:
>
> - power on: normal activity (power led on, spindle runs and drive led lights for few seconds, then stop)
> - connected to a C64: drive resets with the computer normally
> - attempting to load halts at "SEARCHING FOR": drive spins (with leds on) but the stepper doesn't move. Only way out is to reset the computer.

Last month a friend and I fixed an SX-64 where the drive was behaving
that way. It reset properly, you could read the error channel but as
soon as you tried to actually load something from a disk it hung.

In our case the problem was... the 6502. Once we replaced the CPU
everything worked, put the old CPU back in and the problem was back. We
never explored it in detail, but wondered whether the SO-pin on the 6502
the 1541 uses to tell the CPU that a Byte is ready stopped working. He
kept the CPU since there are other systems were it might still be useful
for.

So if the CPU is in socket, try a different one.

  Gerrit



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Re: Two 1541-II drives with problems

silverdr-2
Right, good point! Checking the error channel can give a good hint too!

On 20 April 2014 11:09:23 CEST, Gerrit Heitsch <[hidden email]> wrote:
On 04/19/2014 02:14 PM, Ville Laustela wrote:

Hello!

I found out that I own two Commodore 1541-II disk drives, both in a non-working state.

Testing with a measured-good PSU, I got the following results with both drives:

- power on: normal activity (power led on, spindle runs and drive led lights for few seconds, then stop)
- connected to a C64: drive resets with the computer normally
- attempting to load halts at "SEARCHING FOR": drive spins (with leds on) but the stepper doesn't move. Only way out is to reset the computer.

Last month a friend and I fixed an SX-64 where the drive was behaving
that way. It reset properly, you could read the error channel but as
soon as you tried to actually load something from a disk it hung.

In our cas e the problem was... the 6502. Once we replaced the CPU
everything worked, put the old CPU back in and the problem was back. We
never explored it in detail, but wondered whether the SO-pin on the 6502
the 1541 uses to tell the CPU that a Byte is ready stopped working. He
kept the CPU since there are other systems were it might still be useful
for.

So if the CPU is in socket, try a different one.

Gerrit



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Re: Two 1541-II drives with problems

William Levak
In reply to this post by silverdr-2
On Sun, 20 Apr 2014, [hidden email] wrote:

> The easiest way to recover from the head being positioned above usable track
   range is to issue an explicit initialization command "I".

That doesn't always work.  I have had instances when "I" does not work,
but block read to track 1 does.


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Re: Two 1541-II drives with problems

Ville Laustela
In reply to this post by silverdr-2

Hello.

And thanks for your thoughts, everybody.

I actually have two (very old) oscilloscopes, but both are in storage now so I have no chance of getting them up and running now. Also I have very little idea on using those.

I have heard of the problem where the drive head gets driven out of its normal way, and can't find the directory. I think I had that once but it still gave me some kind of error reply, so I don't think it's not related to what I have at hand now.

I did some work on the drives today, but I am not sure if this can be called progress.

I socketed the U6 6522 on one drive (I'll call it the drive 2, it's the one that has broken top cover and it's missing the locking lever). The one on which I already replaced the small U7 logic chip. De-soldering the chip wasn't as painful as I called it (actually I did that faster than any previous chip removal, didn't broke any traces and I even managed to extract the chip undamaged!).

I think I had mis-diagnosed the drive 2. It had a flaky power switch, and sometimes it didn't start right away (both leds stayed on). I thought this was a matter of the broken power switch, and it usually started fine after couple of tries. But as I now removed the switch and wired it to permanently on, it doesn't start (both leds stay on). Perhaps I just magically got it up before by reseting it by turning it on and off?

The drive 2 still does not work (leds stay on), and it seems to be not related to the U6 6522, as I tested it with a working 6522 from a working-1541. I also tested the extracted 6522 on the 1541 drive and it works (drive powers up, and thrue a ZoomFloppy I got a directory listing without any problems). So at least I have a spare 6522 chip now.

I think I'll now concentrate on the better looking drive 1, and get on socketing it's chips.

(Sorry if the text above was hard to follow :)

--
Ville



[hidden email] kirjoitti 20.4.2014 kello 11.58:

>
>
> On 19 April 2014 14:14:23 CEST, Ville Laustela <[hidden email]> wrote:
>
>> - power on: normal activity (power led on, spindle runs and drive led
>> lights for few seconds, then stop)
>
> That's good. Means that it found no internal problems. The worst usually is when the led remains on all the time
>
>> - connected to a C64: drive resets with the computer normally
>
> You mean when you power the computer on? There goes a RESET line along the cable. If the drive passes its POST at power up, you can quite safely bet that it will pass the reset correctly as well. At least I haven't seen a single case that would not.
>
>> - attempting to load halts at "SEARCHING FOR": drive spins (with leds
>> on) but the stepper doesn't move. Only way out is to reset the
>> computer.
>
> Which tells us that the communication from the computer to the drive works more or less fine (drive received expected commands and tries to deliver results). The problem looks like the communication back doesn't work. This would indeed point to the ICs mentioned below.
>
>>
>> By the Ray Carlsen's website
>> (http://personalpages.tds.net/~rcarlsen/cbm/1541/1541-II/1541-II.txt)
>> these symptoms point to either U7 logic chip (7406) or U6 VIA (6522).
>> On one of the two drives I replaced the U7 chip but that had no effect.
>>
>> Before I start a (lenghty, painful, boring...) removal of the 6522 VIA,
>> I would like to ask here if anyone would have any other ideas?
>
> If you have a way to check the serial lines with a scope that should shed more light. But.. manage your expectations and be prepared for the boring job anyway. While one can never be 100% sure, odds are good that new VIA is your friend there.
>
> --
> Sent from mobile phone (so please have understanding).
>
>       Message was sent through the cbm-hackers mailing list


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Re: Two 1541-II drives with problems

Spiro Trikaliotis
In reply to this post by silverdr-2
Hello,

* On Sun, Apr 20, 2014 at 11:52:55AM +0200 [hidden email] wrote:
> Right, good point! Checking the error channel can give a good hint too!

Exactly.

First try: Try to speak with the drive without and disk interaction:

1. RESET the drive & the computer (i.e. by switching everything off and
   on)

2. Type the following program:
   10 OPEN 1,8,15
   20 GET#1,A$:PRINT A$;:IF ST<>64 GOTO 20
   30 CLOSE 1

3. RUN it.

4. Do you get any output (if yes: What?)
   Or does your drive hang?

   If you get any output, the IEC connection works, and you have problem
   with the drive itself. (For example, the S.O. bit on the 6502, or
   the DC VIA). If your drive (or computer) hangs, then you have a
   problem with the IEC bus (the 7406 drive, the BC VIA, ...)

Tell us your result, and we might be able to help you more.

Regards,
Spiro.

--
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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Re: Two 1541-II drives with problems

Ville Laustela

Hi.

Thanks Spiro, that program sounds like a great idea.

I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two drives.

I typed in the program and run it and the first run gives "73,CBM DOS V2.6 1541,00,00" and the following runs give "00, OK,00,00". So it appears that the fault must lie at the DC VIA or the S.O bit on the 6502 (can I check this with a logic probe?).

Regards,
Ville



Spiro Trikaliotis <[hidden email]> kirjoitti 21.4.2014 kello 23.04:

> Hello,
>
> * On Sun, Apr 20, 2014 at 11:52:55AM +0200 [hidden email] wrote:
>> Right, good point! Checking the error channel can give a good hint too!
>
> Exactly.
>
> First try: Try to speak with the drive without and disk interaction:
>
> 1. RESET the drive & the computer (i.e. by switching everything off and
>   on)
>
> 2. Type the following program:
>   10 OPEN 1,8,15
>   20 GET#1,A$:PRINT A$;:IF ST<>64 GOTO 20
>   30 CLOSE 1
>
> 3. RUN it.
>
> 4. Do you get any output (if yes: What?)
>   Or does your drive hang?
>
>   If you get any output, the IEC connection works, and you have problem
>   with the drive itself. (For example, the S.O. bit on the 6502, or
>   the DC VIA). If your drive (or computer) hangs, then you have a
>   problem with the IEC bus (the 7406 drive, the BC VIA, ...)
>
> Tell us your result, and we might be able to help you more.
>
> Regards,
> Spiro.
>
> --
> Spiro R. Trikaliotis
> http://www.trikaliotis.net/
>
>       Message was sent through the cbm-hackers mailing list


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Re: Two 1541-II drives with problems

Gerrit Heitsch
On 04/22/2014 06:49 PM, Ville Laustela wrote:
>
> Hi.
>
> Thanks Spiro, that program sounds like a great idea.
>
> I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two drives.
>
> I typed in the program and run it and the first run gives "73,CBM DOS V2.6 1541,00,00" and the following runs give "00, OK,00,00". So it appears that the fault must lie at the DC VIA or the S.O bit on the 6502 (can I check this with a logic probe?).

Well, the SO-Bit needs to change state when the drive is running and the
DOS has enabled that functionality through CA2 of the VIA that controls
the drive. It is supposed to indicate that a Byte is ready to be read.
That doesn't mean that the 6502 is reacting to it though, that part
happens inside the CPU where you cannot reach with a logic probe...

You should grab the schematics for the 1541 long board. That one doesn't
have the gate array, it does everything in discrete TTL which makes it
much easier to find out HOW it's done.

  Gerrit



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Re: Two 1541-II drives with problems

Rob Eaglestone
Makes me wonder what it would take to put most of the 1541 logic onto a FPGA or CPLD... using SystemVerilog, for example. 

(And is my mentioning that considered a proof of my insanity?


On Tue, Apr 22, 2014 at 12:14 PM, Gerrit Heitsch <[hidden email]> wrote:
On 04/22/2014 06:49 PM, Ville Laustela wrote:

Hi.

Thanks Spiro, that program sounds like a great idea.

I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two drives.

I typed in the program and run it and the first run gives "73,CBM DOS V2.6 1541,00,00" and the following runs give "00, OK,00,00". So it appears that the fault must lie at the DC VIA or the S.O bit on the 6502 (can I check this with a logic probe?).

Well, the SO-Bit needs to change state when the drive is running and the DOS has enabled that functionality through CA2 of the VIA that controls the drive. It is supposed to indicate that a Byte is ready to be read. That doesn't mean that the 6502 is reacting to it though, that part happens inside the CPU where you cannot reach with a logic probe...

You should grab the schematics for the 1541 long board. That one doesn't have the gate array, it does everything in discrete TTL which makes it much easier to find out HOW it's done.

 Gerrit




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Re: Two 1541-II drives with problems

Gerrit Heitsch
On 04/22/2014 08:00 PM, Rob Eaglestone wrote:
> Makes me wonder what it would take to put most of the 1541 logic onto a
> FPGA or CPLD... using SystemVerilog, for example.
>
> (And is my mentioning that considered a proof of my insanity?

Once you have the two 6522, the 6502 and the RAM/ROM taken care of, the
rest is not that complicated. Besides the analog part of course, you'll
probably have to keep that analog.

  Gerrit



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Re: Two 1541-II drives with problems

silverdr-2
In reply to this post by Rob Eaglestone
------------------------------------------------------
From: Rob Eaglestone [hidden email]
Reply: [hidden email] [hidden email]
Date: 2014-04-22 at 20:00:48
To: [hidden email] [hidden email]
Subject:  Re: Two 1541-II drives with problems

> Makes me wonder what it would take to put most of the 1541 logic onto a
> FPGA or CPLD... using SystemVerilog, for example.
>  
> (And is my mentioning that considered a proof of my insanity?

Probably. But I bet you found a good company here ;-)

--  
SD!

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RE: Two 1541-II drives with problems

Baltissen, GJPAA (Ruud)
In reply to this post by Gerrit Heitsch
Hallo Ville,


Gerrit wrote:
> You should grab the schematics for the 1541 long board. That one doesn't have
> the gate array, it does everything in discrete TTL which makes it much easier to
> find out HOW it's done.

Or visit: http://www.baltissen.org/newhtm/1541a.htm :)


Met vriendelijke groet / with kind regards,
Ruud Baltissen


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Re: Two 1541-II drives with problems

Spiro Trikaliotis
In reply to this post by Ville Laustela
Hello Ville,

* On Tue, Apr 22, 2014 at 07:49:28PM +0300 Ville Laustela wrote:
 
> I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two drives.

If you told me that you have ZoomFloppy, I would have said to issue

        cbmctrl reset
        cbmctrl status 8
        cbmctrl status 8

from a command line window in order to see the same output. You could
not have to type in the "program" in WinVICE.

But, while you have OpenCBM, you might want to try to issue

        cbmctrl download 8 0xc000 0x4000 ROM.BIN

(note: This command needs some time (2 minutes, IIRC) to execute, so
keep patient!)

and have a look into the resulting file "ROM.BIN". It should be exactly
16384 byte long.

You could also retry this command multiple times. For this, issue the
following two commands again and again:

        cbmctrl download 8 0xc000 0x4000 ROM2.BIN
        fc /b ROM.BIN ROM2.BIN

Each time, fc should output that the files are identical.

If this test works, then you can be (almost) sure that the IEC part (the
communication part) is actually working.


Now, having verified this, you can try to check the drive itself. This
is the hard part. You could try to format a disk (either with

        cbmctrl pcommand 8 n0:test,00

or with
        cbmformat -p 8 test,00

Personally, I would prefer cbmformat.)

Does the head bump now? Does the stepper move in any way?

Why do I want to format? Because format will bump the head even without
reading from the disk beforehand. Thus, if for example S.O. is not
working, your drive should at least bump and thus, move the R/W head.

BTW: What 1541 drive is it? 1541, 1541-2, 1541C? It would be best if you
could also send me the ROM.BIN file from above. The reason why I ask: I
want to know if your drive has the "track 1" sensor or not. This might
change the way the head bumps.


There would be possibilities to do even more checks with software, but I
doubt that software does not exist yet.

 

Regards,
Spiro.

--
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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Re: Two 1541-II drives with problems

Ville Laustela

Hello Spiro.

Here's a short reply, too late for intensive testing now.

Sorry if I forgot to mention the ZoomFloppy. I'll send you the ROM, Spiro. It didn't take very long to transfer, and yes, it is 16384 bytes. Didn't do file comparasion as OS X's terminal didn't accept it as fc /b, didn't go to search for correct syntax now. It is a 1541-II (as per the topic).

If I run the cbmformat command, I can see that the drive head makes a very little step (but won't move anywhere). Spindle runs for a second or two, drive light comes up but then it stops (looks just like it resets) and ZoomFloppy leaves on blinking (cbmformat halts, but gives no errors or anything). I can't get any error messages as giving cbmctrl status 8, it notices that the previous command was interrupted, and does a full reset. Attempting a cbmctrl dir 8 just makes the drive run (both lights on) and it goes on forever (ZoomFloppy starts blinking).

One thing I also wonder: if I power up the drive with a floppy in and the door closed, it keeps running and both lights stay up. That sounds weird, I don't remember 1541s doing that? If I open the drive door, it stops. How can it see when the door is open, I thought this doesn't have a disk sensor?

I have now also socketed the DC 6522 VIA, and replaced it with another one. Still no chance. But, couple of times today cbmctrl showed me "drive not ready", which was something new. But then it went away again, almost like a bad contact somewhere. I am really getting a bit lost now, so many chances what might be wrong with this :/

--
Ville


Spiro Trikaliotis <[hidden email]> kirjoitti 23.4.2014 kello 22.22:

> Hello Ville,
>
> * On Tue, Apr 22, 2014 at 07:49:28PM +0300 Ville Laustela wrote:
>
>> I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two drives.
>
> If you told me that you have ZoomFloppy, I would have said to issue
>
>        cbmctrl reset
>        cbmctrl status 8
>        cbmctrl status 8
>
> from a command line window in order to see the same output. You could
> not have to type in the "program" in WinVICE.
>
> But, while you have OpenCBM, you might want to try to issue
>
>        cbmctrl download 8 0xc000 0x4000 ROM.BIN
>
> (note: This command needs some time (2 minutes, IIRC) to execute, so
> keep patient!)
>
> and have a look into the resulting file "ROM.BIN". It should be exactly
> 16384 byte long.
>
> You could also retry this command multiple times. For this, issue the
> following two commands again and again:
>
>        cbmctrl download 8 0xc000 0x4000 ROM2.BIN
>        fc /b ROM.BIN ROM2.BIN
>
> Each time, fc should output that the files are identical.
>
> If this test works, then you can be (almost) sure that the IEC part (the
> communication part) is actually working.
>
>
> Now, having verified this, you can try to check the drive itself. This
> is the hard part. You could try to format a disk (either with
>
>        cbmctrl pcommand 8 n0:test,00
>
> or with
>        cbmformat -p 8 test,00
>
> Personally, I would prefer cbmformat.)
>
> Does the head bump now? Does the stepper move in any way?
>
> Why do I want to format? Because format will bump the head even without
> reading from the disk beforehand. Thus, if for example S.O. is not
> working, your drive should at least bump and thus, move the R/W head.
>
> BTW: What 1541 drive is it? 1541, 1541-2, 1541C? It would be best if you
> could also send me the ROM.BIN file from above. The reason why I ask: I
> want to know if your drive has the "track 1" sensor or not. This might
> change the way the head bumps.
>
>
> There would be possibilities to do even more checks with software, but I
> doubt that software does not exist yet.
>
>
>
> Regards,
> Spiro.
>
> --
> Spiro R. Trikaliotis
> http://www.trikaliotis.net/
>
>       Message was sent through the cbm-hackers mailing list


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Re: Two 1541-II drives with problems

silverdr-2
------------------------------------------------------
From: Ville Laustela [hidden email]
Reply: [hidden email] [hidden email]
Date: 2014-04-23 at 22:02:16
To: [hidden email] [hidden email]
Subject:  Re: Two 1541-II drives with problems


> Sorry if I forgot to mention the ZoomFloppy. I'll send you the ROM, Spiro. It didn't take  
> very long to transfer, and yes, it is 16384 bytes. Didn't do file comparasion as OS X's  
> terminal didn't accept it as fc /b, didn't go to search for correct syntax now.

Under OSX you can use cmp command.

$ cmp file0 file1

--  
SD!

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Re: Two 1541-II drives with problems

Spiro Trikaliotis
In reply to this post by Ville Laustela
Hello Ville,

* On Wed, Apr 23, 2014 at 11:01:24PM +0300 Ville Laustela wrote:
 
 
> Sorry if I forgot to mention the ZoomFloppy. I'll send you the ROM,
> Spiro. It didn't take very long to transfer, and yes, it is 16384
> bytes.

I just checked: It is a plain 251968-03 ROM; that is, there is no sensor
for track 0.

> Didn't do file comparasion as OS X's terminal didn't accept it
> as fc /b, didn't go to search for correct syntax now. It is a 1541-II
> (as per the topic).

I thought you were using WinVICE to test? That's why I assumed you are
on Windows, and I proposed "fc". For Unixoids, I would have proposed
"diff" instead, although I do not know if it exists on MacOS, too.

Thanks to silverdream, we now know that you can also use "cmp".

> If I run the cbmformat command, I can see that the drive head makes a
> very little step (but won't move anywhere).

That's bad. That's why I asked about the ROM version: If it were with a
track 0 sensor, then the little step might make sense if the head is
already on track 0 (or 1). However, your drive does not have this
sensor. Thus, the head should bump. Unfortunately, it does not.

Thus, my possible candidates would be (according to the schematics on
http://unusedino.de/ec64/technical/misc/c1541/1541-II-340503.gif):

- the DC VIA (6522, U8)
- the gate array (U10)
- U13 which seems to be the amplifier for the stepper motor
- the drive mechanics themselves.

Of course, one could more tests to find out what the 6502 reads to be
more sure.

However, I would really bet on the 6522. You might want to swap it with
the 6522 in U6. If the serial communication does not work then, it is
the 6522.

But, as you state below that you have swapped in a 6522, then the
next-best bet comes into play: the gate array. It is responsible for the
stepper motor as well as for the (digital) R/W logic, as well as
generating the BYTE signal (which is directly connect to "S.O." on the
6502).

However, I do not know where you could get a replacement for that one.

In order to find out what we are searching, you might also want to test
your PCB against a known working drive mechanics, if you have some
access to it?


> One thing I also wonder: if I power up the drive with a floppy in and
> the door closed, it keeps running and both lights stay up. That sounds
> weird, I don't remember 1541s doing that? If I open the drive door, it
> stops. How can it see when the door is open, I thought this doesn't
> have a disk sensor?

It does not use a disk sensor. Instead, it only looks for the write
protect light sensor for changes, and then it looks if it can read
anything from disk. If it gets byte after byte, it knows a disk is
inserted.

I have not seen this behaviour myself, so I cannot tell anything about
the details. Furthermore, I am not sure if the 1541-II actually should
have this behaviour or not.

> I have now also socketed the DC 6522 VIA, and replaced it with another
> one. Still no chance. But, couple of times today cbmctrl showed me
> "drive not ready", which was something new. But then it went away
> again, almost like a bad contact somewhere. I am really getting a bit
> lost now, so many chances what might be wrong with this :/

The problem is we would need some test programs to find out what the CPU
is actually seeing from the drive in order to be able to diagnose this
better. I don't think many test programs exist.

Groepaz, don't you work on test programs for the 6522 for VICE? Can they
be made to work with the floppy drive?


Regards,
Spiro.

--
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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