Disk II Positioning Disk fault?

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Hi, Iv got three Disk II's for my Europlus. Two of them seem quite new and work fine. The third drive seems much older than the others. Its sounded very noisy and generally unhealthy. In fact it had real problems reading any disk. So I have serviced them all with SpeedyG's guide. No change in that drive. So I went onto the next step, speed calibration with LockSmith 6.0. I got a pattern similar to drive belt problems. (wide line of "sand" almost identical to the screen shot on SpeedyG guide.) Not to be de-tired I calibrated the speed. Then I tried to format a disk or read one. Nothing, the disk is not recognised. Then I noticed that the Positioning Disk seems to be just spinning and occasionally the Positioning Slide moves. Its as if the drive can't "scene" the grove. One occasion the slide ball was stuck in the hole in the Positioning Disk

any ideas?

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speedyG's picture
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Re: Disk II Positioning Disk fault?

Hello pfarady,

there seem to be 2 problems joining each other....

the first one is rather easy to solve : the positioning
If you remember from my pages the pictures you´ll also remember that the positioning ball
is fixed to the rearside of the read/write head.

You´ll also remember the detailed pictures about that steelplate in copper color. It´s recommended in you case to slightly bend that steel plate that way that the ball gets a slight higher presure to the positioning disk by
bending it slightly downwards towards the positioning disk. But it´s required to dismount the head like displayed
at my page. I´d als recomend to clean the positioning diesk itself carefully and applying a very tiny but of grease
in the sliding-groove.

That would solve the first part of the problem.

The second part of the problem will be the track zero alignment.
There might be also instedad a problem with the read /write compensation......
the problem itself splits in 2 parts:

recognizing the track zero ( regular detecte by some drives with a light barrier at the rear end of the read/write head
and at the end where the sliding steel bars are fixed at the chassis
or
alternate by software allocation.

You remember the 3 very tiny drill marks in the positioning disk that indicate the coorect position ?
The descrition explains how to untighten the screws of the positioning stepper motor and allocating by turn of
the stepper motor the head to match exactly the proper drilled notch at thepositioning disk and fixing the screws and verify of the correct distance by use of distance blades st the positioning limiter steelplate alocated at the
steelbars st the top ?

Then after performing this 2 tasks you may remount the drive for testing of the read/write compensation.
For that measurement you will need an oscilloscope and perform a speedalignment test to get permanent
read/write operations performed while adjusting the to trimming resistors at the analog board to get optimum
performance / signal at the oscilloscope.

then the problem should be solved.
sincerey
speedyG

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Re: Disk II Positioning Disk fault?

thanks for the directions, the first bit was along the lines of thought I had and the second I was hoping to avoid. Never mind all the fun of owning this stuff.

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Re: Disk II Positioning Disk fault?

All fixed now and running sweet. Stripped the drive down as per instructions, cleaned and greased. No need to do the track 0 (than God). All the drives I have are running a bit fast, is it worth tuning them up with Locksmith? Or as they can read/write disks, leave well alone? If it isn't broke and all that.

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Re: Disk II Positioning Disk fault?

Hello pfarady,

glad to hear that it´s solved.

About the speed:
slight bit to fast is not too bad, but in fact it´s recommended to
better get the drives a very tiny bit slower than normal.

Ideal is a value of 1% to 0,5 % less than normal.

If you did read the explenations at the beginning of the page about speed adjustment
you´d remember that if the speed is too fast - there is a small danger that writing
to disk the last sector might overwrite portion written in the first sector by overlaping !

This problem is eliminated if the drive is a tiny bit too slow.

Probably it´s a good idea to reread the first part of that page wwith the explenations....

Another reason is related to the handling of some copy protection shemes......
If the drive is a bit slower Locksmith and other Nibble copy programs can
handle the task of copying that disks better....

sincerely
speedyG

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Re: Disk II Positioning Disk fault?

Hi, I did read the section on setting the speed but just wondered on the merit of "re-tuning" all my drives to slightly slow. The drive I have just fixed still gives a trace on Locksmith like a line of sand. The belt feels fine do you think its shot or the motor showing its age?

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Re: Disk II Positioning Disk fault?

excuse me please.... - but a "line of sand" is like "a chewing gum"....
every person reading such a term has his own "interpretation"....
can you place here a picture or a link to a picture
( probably taken by a handy ? )
speedyG

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Re: Disk II Positioning Disk fault?

ok trying to figure out how to up load a photo.

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Re: Disk II Positioning Disk fault?

Hello pfaraday,

go to this thread:
http://www.applefritter.com/?q=content/heating-issue
view posting #8.
that and the following postings explain how to do it.
speedyG

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Re: Disk II Positioning Disk fault?

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Re: Disk II Positioning Disk fault?

Just for compare:

that was taken at best resolution of locksmith.

I´ve updated my site with a new additional page related to this kind of trouble at:
http://www.appleii-box.de/H084_6_AppleIIDiskService6.htm

hope that helps ahead solving the problem.

speedyG

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Re: Disk II Positioning Disk fault?

Thanks, I'll start with finding a belt and see if it cures the new issue. The drive can read disks but when trying to write a disk it gets to the inner section of the disk the positioning disk seems to get stuck. Then the drive cant write any more data. very odd. Its not the controller card as the other 2 drives work fine.

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Re: Disk II Positioning Disk fault?

That sounds to me like the guide-steel-ball still jumping out from the notchrail....
Did you strengthen the tension of the ball to the rail by bending the steel spring carrier... ?

speedyG

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Re: Disk II Positioning Disk fault?

Yes I did bend it down, it dose not seem to be that its not making that sort of sound. the positioning disk is not spinning its "jogging" as if its reached its limit and keeps trying to go past it?

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Re: Disk II Positioning Disk fault?

If it spun too far on the mounting rod, then that can happen. You'd have to spin it back and pin it somehow. That used to be how Commodore drives got misaligned over time, if I am understanding the problem properly.

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Re: Disk II Positioning Disk fault?

but would that not make it miss track 0? i did notice that when i had the drive to bits that the steel ball was not at the very start of the groove on the disk. it was just behind the track 0 dent. should the ball be hard up against the start of the grove?

and another thing, where are people finding drive belts from? Iv had a good dig about with no luck. 290mm x 3.3mm

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Re: Disk II Positioning Disk fault?

Hello pfarady,

i cant´t help myself, but i still have the impression that you did not read this page carefull:
http://www.appleii-box.de/H084_3_AppleIIDiskService3.htm

otherwise you would have recognized that the postioning limiter ( no.13 in the pictures ) is responsible
to limit the move of the head to to avoid the head get out of the limits....

and the notch indication position of track 0 must be exactly centered below the read/write head
and exactly centered at the middle between the 2 steelbars by adjusting the steppermotor by release and turn
and then after adjustment by fixing the position and tightening the screws again very hard.
The position must be confirmed by measurement with the gage steel ( 0,008 ) !
If this is done correct the trouble should vanish....

drivebelt:
http://www.ebay.de/itm/Antriebsriemen-290mm-Flachriemen-Qualitat-Riemen-Plattenspieler-Turntable-Belt-/361497160251?hash=item542ae8ea3b:g:4jIAAOSwDuJWzstg

speedyG

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Re: Disk II Positioning Disk fault?

Ok, thanks. I presumed as the drive had no problems reading disks written on other drives the track 0 aliment was fine. Therefore I didn't want to open a can of worms by touching the motor. I shall ingestive further.

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Re: Disk II Positioning Disk fault?

Hi, Iv finally got round to getting a scope to test the track zero. Ive tried all sorts of settings but just do not seem to be getting the trace I want. Can some body / SpeedyG tell me the settings I should be using and what probe they have found success with?

Also as part of this I tried to set track zero with the motor but even at is maximum adjustment I can't get the gap between the spindle and the carriage to 0.008, am I just being stupid?

Im still mighty confused to how the drive can read disks and only have issue when writing to the inner tracks, can this rely be track zero problem?

Im determined not to chuck the drive in the bin!

thanks once again

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Re: Disk II Positioning Disk fault?

Hello pfaraday,
at the moment i'm completing a update of a page at the site......
i'll reply within next 24 hours till tommorow evening in detail....
sincerely
speedyG

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Re: Disk II Positioning Disk fault?

Hello pfaraday,

lets first order some points:
The order of the pages in my site are not only just for fun....
the order is given by the total order of the procedures:
1st adjust the speed of the drive
2nd adjust the track zero
3rd adjust the read write compensation

The adjustment of read/write compensation is recommended if speed adjustment fails total
while the speedadjustment is a part of the simple electronic adjustment procedures
the read/write compensation is a rather complex electronic adjustment.

If a drive is not correct adjusted to correct speed and then there is a danger that correct track detaction might fail
not because it's the wrong track
- but because information on the disk is damaged because the drive is too fast
and resulting by that behavious sectors are deleted by "overlapping" sectors
or
- if the drive is too slow the sectors are too short resulting to overstressing
the read write compnsation because the drive is not able to write the information
to the "shortened" track with enough amplitude... see explenation in my pages...

The track zero adjustment is a primary mechanical adjustment procedure and not a electronical adjustment !
I'll explain this here again regarding to the pictures in the page in my site:
You need for the track zero adjustment no scope but you do need a spaceingblade tool - ( gage steel )
it's the blue case with the unfolded spreaded steel spacing blades where the blades have different
thickness imprinted to the steelblades !
see:
http://www.appleii-box.de/H084_3_AppleIIDiskService3.htm

After the analog board has been dismounted, you will see the positioning disk ( indicated as 12 )
the positioning limiter ( indicated as 13 )

There are several pictures of the positioning disk in follow up of the page one that displays the drill notches
that are marked in one picture by drawing as 0, 20, 35 and 40 !
they mark the position where the sliding ball of the head positioning sled will be in the gliding notch - when positioning is correct.

First start by cleaning and greasing the positioning disk like displayed in the pictures !
the when the head is mounted back at the sliding bars ( 1 ) you can turn the positioning disk
( of course with no electric power at the disk ! ) manual till it reaches the position indicated
by the drill notch as 0 !

At that position there will be only very tiny spacing between the axis of the positioning disk (12 )
and the positioning limiter ( 13 ).

Then the screws of the positioning stepper motor ( marked as 15 ) shall be untightend and the
motor shall be slightly turned and gently pushed till that point, where the spacing blade ( gage steel )
with meaurement 0,008 just gently slides in or out between at that space of the axis of thr positioning disk
and positioning limiter and then the screws (15) shall be tightened
to fix this position of the stepper motor rather strong !

Then the disk II shall be mounted completely again according to the pictures and the text and then you may test the drive.

If you want to test the drive by software You must pay attention !
Only the original disks will display correct testing values !

Copied disk can't display valid values due to the fact that the measurement tracks have not been written
with 1/4 track stepping mode at special drive ! Then only testing possible is validating the interchangeability between other adjusted drives and this now adjusted drive.

Then after these two procedures have been completed you have a working drive or the drive still causes problems...
In that case and only in that case it becomes needed to get access to a scope and perform a read/write compensation adjustment procedure.
At my next page that is rather short explained in a brief description.
If you prefer a extended explenation the i'd recommend to download the
"Sams Computer Facts" for the Disk II :

http://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/hardware/storage/disks/Sams%20Technical%20-%20Disk%20II.pdf

and read the detailed description of the scope measurement procedures starting at page 10.

sincerely
speedyG

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