Pretty much the subject.
Here's what happened:
In the morning, I copy the system master disk to the same drive three times.
I do the same in the afternoon and evening.
Sometime today, I got an error message. I/O error or some other error, I do not remember.
That's an interesting ritual you have there.
I'd be more inclined to suspect the media than the drive, really.
Could there be a dirty head or pressure pad problem? I also suspect the connectors and contacts on the analog board could be developing high resistance..
These are first-line things to look at that cost nothing but a little time.
Hello insanitor,
sounds to me like a modified mild form of "burn in testing" like formerly used with harddisks...
up to this point i do side with the previous postings....
there are several points a disk II might fail in such a test.....
here are some possible problems and their possible "solutions"....
1. the cable from Analog board" to read/write head is not schielded and it transmits delicate signal...
possible solution: changing that very thin cable to a very thin shielded special microphon-cable
( with isolated 4 "core" wires !)
the problem: this special shielded very thin cables are very rare (!) and very extreme expensive (!)
hard to get (!) and you have to find one, that
is exactly same flexible like the unshielded one formely used and to be replaced
and you have to be very careful while soldering ( the read/write head is very sensible ! )
short research:
http://ex-en.alliedelec.com/search/productdetail.aspx?SKU=70004649#tab=specs
or
http://www.gotham.ch/en/index.php?section=docsys&cmd=23_details&id=15
-It is even not sure that this cables will fit the needs....
- first cable seems not to be flexible enough
and second seems to fit ... - if it is thin enough
- it must be previously issued some questions to the seller:
is the "total"-cable ( refering to the outer diameter of the cable )
really very thin ( less 3mm ) and very extreme flexible ?
- and shielding of that cable must be connected to Ground of the analog board
- but none of the four "core"-cables in the cable is connected to ground
- therfor there must be a fifth connection made to the shielding of that cable isolated from the other four cables
- and the connection to Ground must be made at the analog board side
- at the read/write head the shielding must remain without connection staying isolated from the four "core" wires ! - and being covered with shrinkhose for pretection against unwanted contacts !.
2. as explained the signals to the read/write head are very sensible - so at most drives the
read/write compensation signal is just adjusted in a "standard general" way ....
- as far as you tell not to be technician i would give advice to only let experienced tecnician
perforn the task: adjusting the read/write compansation at the analog board with control at a oscilloscope
as explained in my disk pages - this optimizese the signals from and to the read/write heads cleaing them from unwanted spikes and "dirt impulses"....
3. often forgotten: if disk drive is dismounted often the schielding plate is removed to attempt the parts below...
and often its not realy mounted back properly.... it´s also good idea to get better electrical connection of the shielding plate to "solid electrical ground" - it´s funny that engineers at Apple didn´t be aware of the leaking connection between shielding plate and ground... the diskframe is only bad electrical connection:
solution: solder a flexible wire to the shielding plate and at the other end of the ( rather short ! ) flexible wire mount a pin- connector and add ( close to the large filtering capacitors at the analog bord at their minus pol ( which is the general ground of the drive ) a pin where that wire connector may be attached to....
this ensures nmuch better operation of the shielding function of the shielding plate....
Hint to find Ground at the analog board: Pin 1,3,5 and 7 at the connector of the analog board to the plug of the cable to the interface are connected to Ground !
4. Anyhow it´s recommended to read my diskpages to understand the functions of the disk I drives and to carry out the adjustments and cleaning procedures and adjustments as far as possible to the own abilities...
http://www.appleii-box.de/H084_1_AppleIIDiskService1.htm
the cleaner and better adjusted the drive - the better the performance...
and just besides also another hint: some guys equipped in former days their drives with longer flatribbon cables
that´s not a good idea....
this cable should be really not longer than 2 feet ( = 60 cm )......
and even the guys at Apple recognized the problem of unshielded flatribbon cable to the drives ....
at least if using the drive roughly and often its better to replace the old unshielded "rainbow" cables with the later used gray flatribbon cables with the attached "mounting plates" - they are shielded and perform their duty much better than the old "rainbow" like cables....
also to be mentioned here.... often in former days users have forgotten while dismounting cable from disk drive to interface from the drive to remount back the inductive core ! That´s the cluby ferron ring where the cable has been wrinkled several times through before being attached to the analog board....
that inductive core shall be mounted and the cable should make 3 turns through that core and be mounted between the analog board and the fixing clamp at the rearside of the case !
remark:
i have repeated this text at page :
http://www.appleii-box.de/H084_4_AppleIIDiskService4.htm
with some added explaining pictures...
all this points will lead to better and more reliable performance of the DISK II drives.
sincerely
speedyG
a9m0107... Not disk ii.
The ferrite core on this drive can only be installed one way or the back plastic will crack.
I have opened up plenty of these and there is no way to loop the wire three times through the ferrite core. The connector will not allow it.
Hello insanitor,
sorry, was my fault...
i will add that drive in a few days too...
speedyG
Thanks. However, you have given me a few ideas.
If the problem is RF interference, I can attempt to install additional metal shielding.
There is a piece of metal between the analog board and the rest of the unit.
If it is doubled, let's say from an extra drive I have, then maybe it would be enough.
Also, if I install another piece of metal around the connector that goes to the head, maybe that will accomplish to a lesser degree, that wire you spoke of to obtain shielding.
Also, if I take the ground screws attached to the cable and sanded them as well as their connection to ground, then maybe the resistance would go down.
My experience with these drives says a good cleaning of all the connectors and grounds is all that's needed. Check the head contact against the disk. And clean the hub/spindle. Make sure nothing is lifting the pressure pad as it moves with the head.
I'm real big on cleaning connectors, because, the disk is a mechanical device that vibrates and gets banged around when you swap disks. This creates microscopic movements in the connectors and they can and do develop high resistance (and oxidation) over a very long time. 15 - 20 years. Clean clean clean!
Nothing additional need be added. Most of the shielding you see is because of the plastic casing, unlike the metal case (of the older Disk II that provides its own shield effect. And note that the head wires are twisted to provide interference protection.
I've also not had to add shielding between the analog board and the rest of the electronics or mechanism. Good grounding connections are all that's needed.
You CAN add extra ground wires as Speedy said. It won't hurt anything. And we did so in some of our RF/laser lab drives many moons ago. Whether it had an effect or not IDK. We just did it.