[sebhc] Z-37 Diag Disk

Dan Lanciani ddl-cctech at danlan.com
Tue Mar 22 23:43:11 CST 2005

|> |> Does the disk so created read ok on another system?
|> |No, it does not.
|> That would argue against a problem with the "data separator"
|> (really clock recovery) circuit.
|Yes. Though I think it means the one-shots may need adjusting (it uses
|trimpots for the write precompensation and pulse width shaping).

The pulse width is unimportant.  I suppose it's possible that the precomp
could be so far off that it makes the written disk unreadable, but...

|taken the write problem to mean that there is more than one thing wrong.

I don't know.  The chances of two things being wrong neither of which
involves any of the swappable parts seem pretty low, unless something
traumatic happened to the board.

|It is
|probably significant that Heath did not use the 2.048 MHz bus clock;
|they instead used a crystal oscillator to get exactly 2.000 MHz.

Well, 2MHz is the correct number to get the standard data rates, but
you probably wouldn't see much of a problem at 2.048.  In fact, I've
read H17 disks (which use the latter) on a standard frequency controller
and they are well within the range of the PLL.

|> Did you try single as well as double density?
|No. That could be another thing to try.

It should factor out the precomp generator.

				Dan Lanciani
				ddl at danlan.*com
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