1541 bad R/W head

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1541 bad R/W head

Francesco Messineo
Hi all,
I've fixed a couple of 1541 today. Well, actually one can't be fixed
because the R/W head measured 15.4 kohms instead of the usual 32 ohms.
So it seems it isn't the little cable interrupted too.
I guess the only option is finding a new Mitsumi/Newtronics D500
mechanic and substitute it. Or does anyone know a better solution? Any
idea why a R/W head dies?
I've found someone put an LS00 in place of a 06 on that one, but other
than that, the electronics looked ok.
Thanks
Frank

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Re: 1541 bad R/W head

MiaM
Den Sun, 25 Feb 2018 18:56:54 +0100 skrev Francesco Messineo
<[hidden email]>:
> Hi all,
> I've fixed a couple of 1541 today. Well, actually one can't be fixed
> because the R/W head measured 15.4 kohms instead of the usual 32 ohms.
> So it seems it isn't the little cable interrupted too.
> I guess the only option is finding a new Mitsumi/Newtronics D500
> mechanic and substitute it.

Depending on how skilled you are with mechanics, you might get away
with using the head from another kind of drive?

> Or does anyone know a better solution? Any idea why a R/W head dies?

Don't know why but sometimes it also happens on tape recorders.



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Re: 1541 bad R/W head

silverdr@wfmh.org.pl
In reply to this post by Francesco Messineo

> On 2018-02-25, at 18:56, Francesco Messineo <[hidden email]> wrote:
>
> I've fixed a couple of 1541 today. Well, actually one can't be fixed
> because the R/W head measured 15.4 kohms instead of the usual 32 ohms.
> So it seems it isn't the little cable interrupted too.
> I guess the only option is finding a new Mitsumi/Newtronics D500
> mechanic and substitute it. Or does anyone know a better solution?

You may try to replace the head. Is this the "turn" or "push" type of mech? I think I have somewhere an incomplete "push" mech, which should have a working head.

> Any idea why a R/W head dies?

Happens. Rarely but happens. To other types of tightly wound coils too.

--
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Re: 1541 bad R/W head

Francesco Messineo
On Sun, Feb 25, 2018 at 8:22 PM,  <[hidden email]> wrote:

>
>> On 2018-02-25, at 18:56, Francesco Messineo <[hidden email]> wrote:
>>
>> I've fixed a couple of 1541 today. Well, actually one can't be fixed
>> because the R/W head measured 15.4 kohms instead of the usual 32 ohms.
>> So it seems it isn't the little cable interrupted too.
>> I guess the only option is finding a new Mitsumi/Newtronics D500
>> mechanic and substitute it. Or does anyone know a better solution?
>
> You may try to replace the head. Is this the "turn" or "push" type of mech? I think I have somewhere an incomplete "push" mech, which should have a working head.

it's the turn one. The newtronics D500, is the most widely used in the
1541-II, but was used in many 1541s.
I think replacing the head would require a re-alignment of the stepper
too, which is something I can do, but I would rather avoid unless this
happens to be the last disk drive on earth :)
If it were mine, I would probably use it for parts.

>
>> Any idea why a R/W head dies?
>
> Happens. Rarely but happens. To other types of tightly wound coils too.

it's my first encounter with this failure, that's why I wondered. Who
messed with this drive before me, managed to install a 74LS00 in place
of one of the 7406. It rended completely inoperative both the activity
led and the head stepper, but fortunately didn't  ruin the custom
logic array.
I wondered if maybe the same person could have killed the head too...

Frank

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Re: 1541 bad R/W head

silverdr@wfmh.org.pl

> On 2018-02-25, at 20:31, Francesco Messineo <[hidden email]> wrote:
>
>> You may try to replace the head. Is this the "turn" or "push" type of mech? I think I have somewhere an incomplete "push" mech, which should have a working head.
>
> it's the turn one. The newtronics D500, is the most widely used in the
> 1541-II, but was used in many 1541s.
> I think replacing the head would require a re-alignment of the stepper
> too, which is something I can do, but I would rather avoid unless this
> happens to be the last disk drive on earth :)

It's not /that/ hard. I did it a few times on 5.25 and a lot of times on 3.5" where people notoriously used to tear the heads out or otherwise, mechanically damage it.

>> Happens. Rarely but happens. To other types of tightly wound coils too.
>
> it's my first encounter with this failure, that's why I wondered.

I ran a workshop back in the times and had much bigger sample, I guess. Literally hundreds (if not four figure numbers) of those passed through it. I remember this type of failure twice, I reckon. So yes - it is a very rare failure. A fraction of a percent.

> Who
> messed with this drive before me, managed to install a 74LS00 in place
> of one of the 7406. It rended completely inoperative both the activity
> led and the head stepper, but fortunately didn't  ruin the custom
> logic array.
> I wondered if maybe the same person could have killed the head too...

Could be. Who knows what (s)he was thinking and connecting (where to).

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Re: 1541 bad R/W head

MiaM
In reply to this post by silverdr@wfmh.org.pl
Den Sun, 25 Feb 2018 20:22:14 +0100 skrev [hidden email]:

>
> > On 2018-02-25, at 18:56, Francesco Messineo
> > <[hidden email]> wrote:
> >
> > I've fixed a couple of 1541 today. Well, actually one can't be fixed
> > because the R/W head measured 15.4 kohms instead of the usual 32
> > ohms. So it seems it isn't the little cable interrupted too.
> > I guess the only option is finding a new Mitsumi/Newtronics D500
> > mechanic and substitute it. Or does anyone know a better solution?
>
> You may try to replace the head. Is this the "turn" or "push" type of
> mech? I think I have somewhere an incomplete "push" mech, which
> should have a working head.

Kind of a rule-of-thumbs: Afaik the "push" type is always Alps while the
"turn" type is never Alps.


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Re: 1541 bad R/W head

silverdr@wfmh.org.pl

> On 2018-02-25, at 21:45, Mia Magnusson <[hidden email]> wrote:
>
>> You may try to replace the head. Is this the "turn" or "push" type of
>> mech? I think I have somewhere an incomplete "push" mech, which
>> should have a working head.
>
> Kind of a rule-of-thumbs: Afaik the "push" type is always Alps while the
> "turn" type is never Alps.

Yes, I think you are right.

--
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Re: 1541 bad R/W head

Konrad B
In reply to this post by silverdr@wfmh.org.pl
2018-02-25 21:19 GMT+01:00  <[hidden email]>:
>
>> On 2018-02-25, at 20:31, Francesco Messineo <[hidden email]> wrote:
>>
>>> Happens. Rarely but happens. To other types of tightly wound coils too.
>>
>
> I ran a workshop back in the times and had much bigger sample, I guess. Literally hundreds (if not four figure numbers) of those passed through it. I remember this type of failure twice, I reckon. So yes - it is a very rare failure. A fraction of a percent.

Few months ago there was a discussion on a local C= user group about a
bunch of 1541-s with defective R/W heads that popped up on an auction
site (these were part of a bigger batch actually and the guy who dealt
with them fixed the remaining ones).
One guy said he knew a (now retired) technician, working in a local
audio/video equipment manufacturer (Unitra) in the magnetic tape heads
department (long time ago...) - and this guy already fixed 10 of the
D500 R/W heads when we had this discussion, I guess this number now
may be 20+ due to the said bunch of broken 1541-s and some other guys
wishing to repair their own units. Process took 3-6 hours per one head
(!)

Regards,
Konrad

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Re: 1541 bad R/W head

Francesco Messineo
On Mon, Feb 26, 2018 at 2:47 PM, Konrad B <[hidden email]> wrote:

> Few months ago there was a discussion on a local C= user group about a
> bunch of 1541-s with defective R/W heads that popped up on an auction
> site (these were part of a bigger batch actually and the guy who dealt
> with them fixed the remaining ones).
> One guy said he knew a (now retired) technician, working in a local
> audio/video equipment manufacturer (Unitra) in the magnetic tape heads
> department (long time ago...) - and this guy already fixed 10 of the
> D500 R/W heads when we had this discussion, I guess this number now
> may be 20+ due to the said bunch of broken 1541-s and some other guys
> wishing to repair their own units. Process took 3-6 hours per one head

and how does one fix a broken head?
Frank

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Re: 1541 bad R/W head

Konrad B
2018-02-26 16:08 GMT+01:00 Francesco Messineo <[hidden email]>:

> On Mon, Feb 26, 2018 at 2:47 PM, Konrad B <[hidden email]> wrote:
>
>> One guy said he knew a (now retired) technician, working in a local
>> audio/video equipment manufacturer (Unitra) in the magnetic tape heads
>> department (long time ago...) - and this guy already fixed 10 of the
>> D500 R/W heads when we had this discussion, I guess this number now
>> may be 20+ due to the said bunch of broken 1541-s and some other guys
>> wishing to repair their own units. Process took 3-6 hours per one head
>
> and how does one fix a broken head?
> Frank

This is a literal translation: remove the coil, install the new one
(no info what he uses for this), measure the gap/polish the surface.
As easy as it is - for the guy that spent most of his life working for
the audio equipment manufacturer (and being a master of the audio tape
heads unit - until he retired).

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Re: 1541 bad R/W head

Francesco Messineo
On Mon, Feb 26, 2018 at 4:40 PM, Konrad B <[hidden email]> wrote:

> 2018-02-26 16:08 GMT+01:00 Francesco Messineo <[hidden email]>:
>> On Mon, Feb 26, 2018 at 2:47 PM, Konrad B <[hidden email]> wrote:
>>
>>> One guy said he knew a (now retired) technician, working in a local
>>> audio/video equipment manufacturer (Unitra) in the magnetic tape heads
>>> department (long time ago...) - and this guy already fixed 10 of the
>>> D500 R/W heads when we had this discussion, I guess this number now
>>> may be 20+ due to the said bunch of broken 1541-s and some other guys
>>> wishing to repair their own units. Process took 3-6 hours per one head
>>
>> and how does one fix a broken head?
>> Frank
>
> This is a literal translation: remove the coil, install the new one
> (no info what he uses for this), measure the gap/polish the surface.
> As easy as it is - for the guy that spent most of his life working for
> the audio equipment manufacturer (and being a master of the audio tape
> heads unit - until he retired).

ok, so there's no hope that there's a tutorial around or a better
explanation, right?
Would be interesting at least to know how to remove the bad coil. I
seem to remember the heads are all filled with epoxy or something
similar..

Frank

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Re: 1541 bad R/W head

silverdr@wfmh.org.pl
In reply to this post by Konrad B

> On 2018-02-26, at 14:47, Konrad B <[hidden email]> wrote:
>
> Few months ago there was a discussion on a local C= user group about a
> bunch of 1541-s with defective R/W heads that popped up on an auction
> site (these were part of a bigger batch actually and the guy who dealt
> with them fixed the remaining ones).
> One guy said he knew a (now retired) technician, working in a local
> audio/video equipment manufacturer (Unitra) in the magnetic tape heads
> department (long time ago...) - and this guy already fixed 10 of the
> D500 R/W heads when we had this discussion, I guess this number now
> may be 20+ due to the said bunch of broken 1541-s and some other guys
> wishing to repair their own units. Process took 3-6 hours per one head
> (!)

Totally interesting... I remember myself re-winding tweeters back then but never a head's coil. Unitra was a company I admired once (although its various branches with varying amount of admiration ;-) Their magnetic heads were not something I'd recommend to anyone but maybe they were all "hand-made", which would explain not only their quality but also the guy's ability to re-build a floppy head. Highly interesting.

--
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