Reversed cables?

[emu]

Hi all,

just (finally) opened my box with two new boards, and both complain
about reversed cables?

I already tried a different set, and the same message comes, first the
J3 is reversed, than the J4 is reversed too?

All my cables are keyed, so I can't put them in wrong.

I'm sure, I'm doing something stupid, didn't use the first board I have
for years :(

Onme set I took of my MV2000, where the drive was working fine, and the
same drive attached

Any idea?


Thanks!

[David Gesswein]

Were these assembled boards with beaglebone you got from me (David Gesswein)
or something else? If so did you change any software on the board?

Does the drive have the terminator resistor installed?

Your ran setup_mfm_read before mfm_read command?

Are both ends of your cables keyed?

For J3 the full error is
** Drive selected without select, is J3 20 pin cable reversed?
On the 20 pin cable is a selected signal that the board is seeing low
when it hasn't asserted any of the select lines. Does the drive have an
activity light and if so is it on?

Schematic is here.
https://www.pdp8online.com/mfm/board/mfm_revd_pcb/pdf/top.pdf

See what voltage is on pin 1 of J3 which is easiest to probe on U5 pin 7.

For J4 its looking to see that both index and write fault signals are
active (low).

Index should only be low for a short period every 16.6 ms. Write fault
should not be low.
Index is J4-20 or U5-5
Write fault is J4-12 or U5-4.

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[emu]

On 2025-04-13 11:02, David Gesswein wrote:
> Were these assembled boards with beaglebone you got from me (David Gesswein)
> or something else? If so did you change any software on the board?

Sorry for the noise :(

Yes, they were form you, and are nice!

I didn't notice, that I actually killed (ripped some wires off) the
working cable, taking it out of the MV2000.

Got a different set of cables, and now it works how it should !

Thanks, and sorry again ...

[Kirk Barrett]

Absolutely fantastic boards!!