Radio Shack TRS-80 Hard Drive Alignment

This is a detailed instructional video released by Radio Shack National Technical Support in 1986. It was provided to Radio Shack repair center technicians in order to better understand how to perform hard drive alignment procedures.

[@BryanChance]

It looks like an old 12volt battery charger. LOL Love these retro tech!!!

[@bokami3445]

loved the soft beep this drive make while reading/writing data to it

[@Nf6xNet]

This is exciting! But I die just a little bit every time they call the hard drive mechanism a "bubble". Did anybody other than Tandy use that terminology? When I was working for Silicon Systems, we called it an "HDA", short for "Head-Disk Assembly".

[@TheBrookshank]

it was a shugart term originating with the 8" 8 megabyte drives. they may have used the term prior to that..

[@Nf6xNet]

Aha! Thank you.

[@vanhetgoor]

Since the Zilog Z80 does not have a protected mode it would be interesting to see how a "protected mode" is added, unfortunately the schematics are not for the public to see. On the GitHub is only the keyboard of the computer project shown.
The point is, that is missing protected mode from the Z80 can not really be added later on, because the protected mode should have had an instruction to work. With this so called "protected mode" an extra circuit is added, but there is not a single instruction to use it, a complete routine is needed to switch protected mode on or off. With this extra I/O circuit some of the write enables are blocked but I am not convinced if this is exactly the same as the protected modes for other micro processors.
For instance the Z80 has only 16 address lines, if I would take some or the I/O lines I could use them to fake extra address lines, but then the Z80 does not have instructions to address 32 bit address lines so the result would be a non functioning 32 bit processor.
The same goes for the I/O. The Z80 could be extended to 65536 I/O addresses with some extra hardware, but it would not be functioning all the time exactly the same as addressing the first 256 I/O addresses.
But wait, there is more!
The Z80 has very little 64 bit instructions, if a 64 bit instruction could be done by processing eight times an 8 bit instruction, then we could say the the Z80 has a secret 64 bit instruction set, but we would be fooling ourselves.

[@nowheremanjk8624]

Ręczna regulacja obrotów silnika dysku... ;-}

[@McVaio]

Yes, those were the times!