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Stepper motor Profile disk acts weird.

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mactjaap:
I bought a Profile disk on EBay

Macintosh Apple Profile A9M0005 Lisa 5MB Hard Drive External Parts or Repair
Please check the photos. I suspect the unit has been dropped. The case has a little damage as shown.
Powers on and makes a lot of noise from drives. No power cord.
Sold As-Is Where-Is What-Is

Damage is shown on the pictures and the disk was not tested. As these disk are not often seen in the Netherlands I decided to give it a try. I have one working profile, a second would be nice.



I won the auction at $102.50 and used my US shipping address to send it to because only US shipping was allowed. Last week it arrived and I inspected it. The power unit, board and disk looked OK. So I decided to power it on. As was stated in the add: Powers on and makes a lot of noise from drives.
I know the first thing to look at is the stepper motor. Does it do its startup routine? It did, but not as I expected.
I made a YouTube  movie to show it. The movie is around 3 minutes long. The stepper motor sometimes, sweeps back and forth. And it also pauses. These pause can take as long as 40 seconds. But the stepper motor finish its job and the ready light will turn solid red.

https://www.youtube.com/watch?v=gUxkSGfzfT0

Who knows what is happening here?


Spoiler alert.
The Profile seems to work OK. LOS 3.1 sees the disk and has formatted it. I can copy on and from the disk

stepleton:
I have one that behaves similarly; it has a few bad blocks and always has for the 25 years that I've owned it. I'm guessing yours must have bad blocks too. Each backward sweep may be to visit a spare block that the ProFile is using as a substitute for a bad block, although I haven't read the ProFile ROM disassembly close enough to know for sure.

Use BLU or NeoWidEx to see the count of bad blocks. If LOS 3.1 works, it won't be all that many. If it's 0, I'll be surprised!

AlexTheCat123:
My ProFile that recently died has a similar (but more severe) behavior and I'm pretty sure this just means that it has some bad blocks.

patrick:
Your drive starts up and recalibrates. The spare table is read, this is the seek at the beginning. Now each block is read and its CRC checked.. You have three spared blocks, these are the seeks to the center (where the replacement blocks reside). Besides that there are a couple of pending bad blocks.  Here it takes significantly more time until the block has been read or timeout occurred. These bad blocks will be replaced by spares in case the next write access fails.

mactjaap:
Thanks for your help! Nice to know that is familiar behavior.
If I check the disk with BLU  indeed it shows a spare count of 20 and spares allocated 1, but 0 bad blocks.


More news about this disk..... Bonus find:
I see that my new Profile disk has a Z8603 on board. It has 2K ROM. This "Piggyback" ROM is necessary if you want to do a low level format.

Quoted from  Patricks web site:


--- Quote ---When the Z8 microcontroller family was introduced in 1979, Flash memory was not invented yet. Internal memory was mask ROM, and for software development either external EPROM memory or an in-circuit emulator system was used. Zilog offered two different mask ROM controllers, the Z8601 with 2kB and the Z8611 with 4kB ROM. For software development, two special prototyping devices were available, which had an external EPROM sitting on the back of the chip. These "Piggyback" devices were the Z8603 (with 2kB 2716) and Z8613 (with 4kB 2732).
--- End quote ---

http://john.ccac.rwth-aachen.de:8000/patrick/Z8emu.htm

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