Disk II drive problems

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Joined: Jan 12 2011
Posts: 30

I am trying to repair 2 x disk II drives where they pass the speed tests I run on them (hooked up as the second drive) but they don't seem to even register when I do an allignment test (or other drive tests I have disks for).

Before condemning the circuitry, and having spent quite some time studying the mechanics of the ones I am trying to fix, I note the two 'stainless' bars on which the stepper motor adjusts the position of the head have a little corrosion on them and the movement of the unit along them is not smooth and in some places faces resistance.

Is there merit in cleaning and lubing these bars (withsomething like deoxit)? On both units, with the case off, when I run the allignment software, the drive seems to try and get the head where it needs it, but never passes the test. I notice the bar retaining screws have green paint from the assembly plant, so I guess their position is critical.

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Offline
Joined: Dec 13 2005
Posts: 256
Re: Disk II drive problems

This maybe something that you have already done but have not mentioned. Head cleaning. It does not take much to foul the heads drives. Just one dirty oxidizing disk can make them have problems in minutes.
Next is Zero track setting. Set with an .008 to .010 gage steel. They say .010, but I had better luck with .008 if I remember correctly it has been quite a few years.

As for the side rails I do not recall any settings with them. I think the paint is show no one has tampered with the drive. As they are round, no real way to move them. 400-600 paper a few swipes to remove any rust.

A bad ribbon cable, or maybe a bad rewrite chip. Socketted chips with black legs need to be cleaned before they fail.

Now if Zero track is set right and everything else is good, the stepper motor is slotted for movement. This adjustment is for stepping from track zero. You can mark it with a line on the the slotted brackets. This way you can return it to same or almost exact spot you moved it from.

Hope this helps.

Take Care

speedyG's picture
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Joined: Nov 16 2011
Posts: 1382
Re: Disk II drive problems

Hello Atomtan,
i agree that in fact there are several points to keep care of at the Disk-II-drives. And there had been a lot of postings in the last months related again and again with similar troubles and repairs.....

I have therefor decided to prepare several pages with pictures and explenations and instructions and basic informations how drives work, how they are aligned and how so do service at them.....

this will come out close to the pages i made about keyswitches and keyboards....
but of course this will take some 3 to 4 days due to the fact, that i do have some fixed appointments within the next days and the creation of such pages will request some time ( specially making detailed drawings ) too....

anyhow my goal will be, to make some kind of basic reference pages that will last for some years as reference to that topic and reduce repeating threads about that.....

so please be patient with me ... i will try to solve this task as soon as possible.... it should be finished at latest till to the end of the upcoming weekend....

i will post then the link to the created pages here in this thread......

sincerely
speedyG

P.S. : getting the Steelbars as mentioned clean and lubing them with machine-oil is one thing that will bring you ahead .... but it´s not the complete story....

correction - later edit:
the correct alignment is also dependent the so called "Track-Zero-Indicator" which is realized by a light-bar-system at the backside of that bars.... but attempting them is really tricky (!)....
added correction:
this is only valid to some of the shugart-drives distributed by Apple as DISK II drives...
the other work by calibration of the positioningdisk ( explained in the pages that will be created now ) and with a kind of "try and error" by software read accesses... ( this will be explained too... ) .... end of edit ----

so my best advice at the moment, is to wait with that task till the pages and explanations are completed....

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Joined: Jan 12 2011
Posts: 30
Re: Disk II drive problems

Many thanks.

speedyG's picture
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Re: Disk II drive problems

Hello Atomtan,

the first page is completed in raw format ( without proofreading ) but with text and pictures
just to get imagination how the stuff will be treated.... feedback welcome....
the other 3 pages will be completed each day one page till Sunday evening the final 4th page shall be finished.
The requested time is caused by the fact that i have to make additional pictures and drawings and of course write the taxt with the explenations....
the first page is located at:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage1.htm

after the forth page is completed, you should be able ta handle any kind of calibration or mantainance related to
the Disk II drives.

sincerely
speedyG

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Re: Disk II drive problems

Nice work. Your years in Germany have given you connectallworditis, though. Feel free to use the space bar once in a while. Smile

speedyG's picture
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Re: Disk II drive problems

david__schmidt wrote:

Nice work. Your years in Germany have given you connectallworditis, though. Feel free to use the space bar once in a while. Smile

Dear David,
thank you very much for the feedback! Your completely correct with your complaint.. its result from the fact that i emigrated to Germany in 1975 and nearly didn´t speak english for more than 30 years.... ( i learned instead German language perfect, and Italian, French and Spanish languages rather well in the last 30 years ) so in fact my practice
was limited only to reading special-topic magazines about electronics and computer in english language.....

I am indeed completely out of exercise and practice and sometimes i feel like a pupil back in school with terrible
spelling.... but it starts getting better... thank God for the edit function here.... otherwise the stuff would be
non-readable.... but i enjoy to get familiar with english conversation again and with some small talk across the pond....

I´ll try to follow up to your advice as soon as possible and as much as possible to recover from the bad style....
again thanks a lot for the reminder.....

sincerely yours speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
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speedyG's picture
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Re: Disk II drive problems

next STRIKE !


the page about speedadjustment of the DISK II is completed.....

http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage2.htm

tommorow the basics about the adjustment of the track zero will be added...
Edited Update:
I guessed to be finished today - but i´ll need a day more due to the complexity of that topic....

enjoy the page .... feedback is welcome !
sincerely
speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

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Joined: Apr 24 2012
Posts: 218
Re: Disk II drive problems

SpeedyG,

First and foremost HUGE thanks for your great effort, this is an awesome help for us that want to know more about our hardware. Is being a great learning tool.
I have a question: in the Apple IIc drives, where is the adjustment screw? I just found my external drive is slow, want to fix it. Thanks again!!

EDIT: I found it and fixed it, using the "Optimum (Recommended)" option. Now, if I use the "300 RPM (normal)" option it gives me lower speeds. Any comments?

Javster

speedyG's picture
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Re: Disk II drive problems

Hello Javstar,
as i explained in the part related to the length of the sectors it´s a big hazard if the drive runs to fast ( due to the risk of overwriting the following sectors ) - so thats the reason that the optimum will always be slower than the exact 300 u/pm ..... then there is also a little margin set even to get a little aditional less speed because the motor and the electronic that drives the motorspeed drifts a little bit by getting warmer and then speeding up the motor ... so that kind of "offset" was also subtracted from the speedadjustment to be sure that even if the drive gets wery warm ( and thats a common problen to all computers of the apple series that the ventilation is very bad and the computer gets rather hot inside ) no overwriting will happen....
sincerely speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
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speedyG's picture
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Re: Disk II drive problems

Hello to all AF-members,
now the important parts of the referencepages related to DISK II Drives are completed....
Basicpage:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage1.htm
speedadjustment:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage2.htm
track zero adjustment:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage3.htm
so at this point i´ll just take a small timeout to solve other tasks waiting to be solved....
in a several days i will also create the final page related to the topic of the read/write compensation
that will explain how to optimize the performance of the electronics of the read/writehead and
common repairs at the analogboard ( for example exchanging the damaged chips if the cable to the
controller was plugged wrong way in and some chips got fried... so some drives might become resurected ... )
the other advantage of optimizing the electronics is that the drive probably can use the tracks 36 to 40
with safe reading and writing... and besides that page will cover some common tricks of protectionshemes
used in the old days to protect gamedisks....
up till then enjoy the pages have fun ... hoping the pages are usefull to the community and reduce threads to the topic of drives ....
sincerely speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

speedyG's picture
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Posts: 1382
Re: Disk II drive problems

Hello to all AF-members,

just a short remark:
the page 3 and the related PDF-File have been updated and some remarks and hints added and the part related
to adjustment with the scope has been added !

sincerely
speedyG

__________________

In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....