MFM Miniscribe HDD does not spin, how to repair??

[XYLOPHONE]

Hello,
I am trying to get my 20MB Miniscribe 3.5" hard drive running again.
The problem is that it doesn't spin up anymore when I power it up. I
disassembled the drive's PCB, and swapped it with the PCB from a
working drive, and the other HD works with both PCBs, so proving the
problem is with the spindle motor itself.
Looking closer at it, I notice that when I power it up, the platter
spins about 1/4 of a revolution, then stops forever, until I power off
and on again. Rotating it manually doesn't fix it.

What could be the problem? I feel that if I can get the HDD to
correctly spin again, I should be able to access the data. This drive
is vintage, so I'm doing all efforts to rescue it.

Thanks for any information, any hint, or any similar situation
experienced.

Luc.

 

[Percival P. Cassidy]

I am trying to get my 20MB Miniscribe 3.5" hard drive running again.
The problem is that it doesn't spin up anymore when I power it up. I
disassembled the drive's PCB, and swapped it with the PCB from a
working drive, and the other HD works with both PCBs, so proving the
problem is with the spindle motor itself.
Looking closer at it, I notice that when I power it up, the platter
spins about 1/4 of a revolution, then stops forever, until I power off
and on again. Rotating it manually doesn't fix it.

What could be the problem? I feel that if I can get the HDD to
correctly spin again, I should be able to access the data. This drive
is vintage, so I'm doing all efforts to rescue it.

"Vintage"!? Wasn't it on one of those drives that Noah kept track of all
the animals?

Have you tried giving the drive a sharp twist about the axis of the spindle?

Perce

 

[Krypsis]

"Vintage"!? Wasn't it on one of those drives that Noah kept track of all
the animals?

Have you tried giving the drive a sharp twist about the axis of the
spindle?

Perce

That should work! Sounds like the OP has what is termed a "stiction
fault". This is caused by the heads being stuck to the platter. The
sharp twist, often with power applied, is enough to break the "stiction"
and allow the heads to float free. Note that, if power is applied when
doing it, there is a risk of damage so treat the device with kids gloves
if you need to do it this way.

Haven't seen this fault in many a long year. No doubt this is due to off
platter head parking mechanisms on all drives nowadays.

 

[Arno]

Hello,
I am trying to get my 20MB Miniscribe 3.5" hard drive running again.
The problem is that it doesn't spin up anymore when I power it up. I
disassembled the drive's PCB, and swapped it with the PCB from a
working drive, and the other HD works with both PCBs, so proving the
problem is with the spindle motor itself.
Looking closer at it, I notice that when I power it up, the platter
spins about 1/4 of a revolution, then stops forever, until I power off
and on again. Rotating it manually doesn't fix it.

What could be the problem? I feel that if I can get the HDD to
correctly spin again, I should be able to access the data. This drive
is vintage, so I'm doing all efforts to rescue it.

Thanks for any information, any hint, or any similar situation
experienced.

Luc.

First, if the data has any real worth, STOP MESSING AROUND and
get help from a professional data recovery service. Chances are you
will just make matters worse.

As you say the drive spins 1/4 revolution, so it cannot be stiction.

Sounds like not all coils in the spindle motor get powered. As
you tried the PCB swap, this would not be a problem with the motor
driver amplifiers. One possibility is a contact problem.
Another one is a possibly broken winding in the motor itself.
Both can be debugged with a multi-tester by mesuring winding
resistances. (If you have no clue what I am talking about, then
you are not qualified to look into this, sorry.)

The contact problem is typically easy to fix temporarily
when located. The broken winding is usually unfixable.

Arno

 

[XYLOPHONE]

First, if the data has any real worth, STOP MESSING AROUND and
get help from a professional data recovery service. Chances are you
will just make matters worse.

As you say the drive spins 1/4 revolution, so it cannot be stiction.

Sounds like not all coils in the spindle motor get powered. As
you tried the PCB swap, this would not be a problem with the motor
driver amplifiers. One possibility is a contact problem.
Another one is a possibly broken winding in the motor itself.
Both can be debugged with a multi-tester by mesuring winding
resistances. (If you have no clue what I am talking about, then
you are not qualified to look into this, sorry.)

The contact problem is typically easy to fix temporarily
when located. The broken winding is usually unfixable.

Arno

Thanks Arno, I'll carefully try to see the contacts.

However, I forgot to mention that, when I first removed the PCB,
everything underneath was covered with tiny DARK BLACK dust, just like
black laser printer toner, or maybe even smaller grain powder. I
gently wiped all that black dust away. When I removed the PCB from the
working HDD, there was a little bit of that black dust, but far less
than on the non-spinning drive.

Does this dust make a click to anyone?

Thanks again...

 

[Jerry Peters]

Thanks Arno, I'll carefully try to see the contacts.

However, I forgot to mention that, when I first removed the PCB,
everything underneath was covered with tiny DARK BLACK dust, just like
black laser printer toner, or maybe even smaller grain powder. I
gently wiped all that black dust away. When I removed the PCB from the
working HDD, there was a little bit of that black dust, but far less
than on the non-spinning drive.

Does this dust make a click to anyone?

Thanks again...

Disintegrated foam perhaps? I seem to remember dismantling a drive
with a thin piece of foam between the pc board and the drive. Might
have been to dampen vibration.

Jerry

 

[Franc Zabkar]

However, I forgot to mention that, when I first removed the PCB,
everything underneath was covered with tiny DARK BLACK dust, just like
black laser printer toner, or maybe even smaller grain powder. I
gently wiped all that black dust away. When I removed the PCB from the
working HDD, there was a little bit of that black dust, but far less
than on the non-spinning drive.

Is there a sintered carbon brush that bleeds the static electricity
off the motor shaft?

- Franc Zabkar

 

[Rod Speed]

Jerry Peters wrote

Disintegrated foam perhaps?

I've never seen any foam deteriorate as comprehensively as that.

I seem to remember dismantling a drive with a thin
piece of foam between the pc board and the drive.

Yes, some Seagates did have that at one time.

Might have been to dampen vibration.

Dont believe it was for that.

 

[GMAN]

Is there a sintered carbon brush that bleeds the static electricity
off the motor shaft?

- Franc Zabkar

I remember those from my Atari ST years. You occasionally would get them
making god awefull sounds when they would wear down and some would suggest
anything from sewing machine oil(3 in 1 oil), to using a dab of facial grease
(Shrugs head???) to stop the squealing.

 

[larry moe 'n curly]

I am trying to get my 20MB Miniscribe 3.5" hard drive running again.
The problem is that it doesn't spin up anymore when I power it up. I
disassembled the drive's PCB, and swapped it with the PCB from a
working drive, and the other HD works with both PCBs, so proving the
problem is with the spindle motor itself.
Looking closer at it, I notice that when I power it up, the platter
spins about 1/4 of a revolution, then stops forever, until I power off
and on again. Rotating it manually doesn't fix it.
What could be the problem? I feel that if I can get the HDD to
correctly spin again, I should be able to access the data. This drive
is vintage, so I'm doing all efforts to rescue it.

Does the RedHill.net.au have any info? HDDguru.com forums are
dominated by people who do HD repair and data recovery.

I would try unplugging the cables from that motor and the motor of a
working drive and compare the resistance readings of their coils.
However resistance measurements don't always tell everything about
coils, and for that you need to ring the coil:

http://members.ozemail.com.au/~bobpar/k7205.pdf

http://repairfaq.org/sam/flytest.htm

Is it possible to replace the motor without opening the drive? I have
a feeling dust would be a problem if even if the motor can be removed
that way.

 

[Arno]

XYLOPHONE wrote:

Does the RedHill.net.au have any info? HDDguru.com forums are
dominated by people who do HD repair and data recovery.

I would try unplugging the cables from that motor and the motor of a
working drive and compare the resistance readings of their coils.
However resistance measurements don't always tell everything about
coils, and for that you need to ring the coil:


Is it possible to replace the motor without opening the drive? I have
a feeling dust would be a problem if even if the motor can be removed
that way.

I think in this particular case, resistancw will be enough, as
a HDD motor has at least 3 identical coils. However if the
resistance is very low, measuring it could be tricky.

For reference: On a 12 year old Fujitsu 3.5" drive I still
have, the windings come in at 3 Ohm. That is within the usable
range of a nomal multitester, if some inaccuracy is
not an issue.

Arno

 

[Rod Speed]

larry moe 'n curly wrote

XYLOPHONE wrote

Does the RedHill.net.au have any info? HDDguru.com forums are
dominated by people who do HD repair and data recovery.

I would try unplugging the cables from that motor and the motor of a
working drive and compare the resistance readings of their coils.
However resistance measurements don't always tell everything about
coils, and for that you need to ring the coil:


Is it possible to replace the motor without opening the drive?
Nope.

I have a feeling dust would be a problem if even if the motor can be removed that way.

Its academic because it cant be.

 

[Franc Zabkar]

I feel that if I can get the HDD to
correctly spin again, I should be able to access the data. This drive
is vintage, so I'm doing all efforts to rescue it.

I still don't see any resistance measurements. Do you know how to use
a multimeter?

Does your drive have a tach sensor? Often there will be a Hall effect
sensor that provides RPM feedback to the controller. Modern drives
sense the back EMF in the non-driven winding, but earlier drives used
discrete sensors.

If you don't understand what to look for, then upload some photos to a
file sharing site so that someone can assist you.

- Franc Zabkar