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Miniscribe 2012 disk defect

In some Miniscribe manuals, the blinking error codes for the drive are explained.
For example, look at the bottom of the manual for the M8425S, at [here].
If (repeat: if) it shares the same error codes as your drive, then the pattern is 1000, which equates to code 8.
 
modem7 said:
In some Miniscribe manuals, the blinking error codes for the drive are explained.
For example, look at the bottom of the manual for the M8425S, at [here].
If (repeat: if) it shares the same error codes as your drive, then the pattern is 1000, which equates to code 8.
Click to expand...

Code 8 - Unable to uncover Track Zero sensor

In some Miniscribe drives that error can be caused by the position indicating flag on the shaft of the head positioning stepper motor having worked its way out of position. On some of the drives where that was the case there was a test jumper block on the controller board of the drive that could be shorted together and then when the drive was powered up it would go into a mode where the position indicating flag could be rotated back into the proper position. The set screwed holding the flag in place on the shaft needed to be loosened, and then the flag could be carefully rotated into or out of the path of the photo detector just until the threshold of the LED turning on or off. Right at that threshold the position indication flag should be back into the proper position and the set screw should be carefully tightened without rotating the flag or the shaft. Then the drive would be powered down and the jumper removed and if everything went just right it would power up normally again after that.

That was 30 years ago when I had to do that to multiple Miniscribe drives. I'm fuzzy on the details now.
 
Hello gslick,
I have a MiniScribe 8425SA disk from a Macintosh SE restauration project.
The failure code is the same - Code 8: Unable to uncover Track Zero sensor. You mentioned in your previous answer the "test jumper" to teach the position of the Track Zero. I find the documentation of this hard disk (https://stason.org/TULARC/pc/hard-drives-hdd/miniscribe/M8425S-21MB-3-5-HH-SCSI1-SE.html) and there is no "test jumper", except I find one more "pin" (it is like a half jumper, only one pin) on the PCB but this is not documented anywhere.
Could you remember if this single pin could be the test jumper? if I shorten to GND then this will be the "test jumper" what you mentioned?
I also find the MiniScribe_III_Product_Manual.pdf (http://www.bitsavers.org/pdf/miniscribe/MiniScribe_III_Product_Manual.pdf) there is a flow chart how the initialisation of the disk made at the startup time. On page 44, is the "Code 8" detection.
I think, with the reset of the position indicating flag could solve my "Code 8" problem.
I don't think so, the IR LED or the IR sensor is wrong, please correct me, if they could fail.

Thank you.
 
I just did a photo about the PCB of the MiniScribe 8425SA and prepared with few labels - for better orientation.
MiniScribe_8425SA_PCB_NOTE.JPG
 
Hope it helps. When I have a Code 8 - Unable to uncover Track Zero sensor, many times the stepper motor is a little bit stucked and performs well in the first searching pattern with a low pulse rate, but when put in a high pulse rate (the second part of the seeking power on rutine) motor stucks and not covering track zero sensor. If it is the case and no error in PCB components, you can use Miniscribe exercise routine JP13 (I dont remember which jumper is in 8425SA, maybe your diagnostic pin in your picture). If it is not a mechanical stuck, then always there is a component near the RIFA PBL 3717 (stepper motor controller) that is burned. You need to check also the track zero sensor (4 pin connector near the 4 pin stepper motor connector)
 
Thank you. Finally, I was able to set the flag to detect Track Zero. Sadly the disk lost its information about the insode disks - or I don't know why - but it is not possible to format it.
I will still try different ways with this unit.
The idea is to do a capacitor renew (recapping) maybe the write amplification and/or the read amplification is not good anymore. It seems the mechanical issues are solved but still something not 100%.
Stepper motor works (fully lubricated), disk drive motor works nicely, spins up easily, everytime. Track Zero flag set and no more Code 8 anymore.
Thank you very much to both of you.
I'll give feedback after the recapping.
 
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