mfm_emu

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ve7gmn

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Jan 31, 2021, 10:09:46 PMJan 31
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I think I might have damaged my unit.

When I start the emu it now says write and step active make sure j2 is not backwards or something along those lines , what should I check


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David Gesswein

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Feb 1, 2021, 7:36:12 AMFeb 1
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Did you check to make sure neither end of J2 cable is plugged in backward?

If this is a new build verify that RN1 and RN2 are installed with pin 1 dot
at the silkscreen dot.

Try it without J1 and J2 cables attached. If you still get the error you will
need to check with test equipment where write and step signals are low.

If it doesn't give the error you will need to check why the signals are low
from the computer.


On Sun, Jan 31, 2021 at 07:09:42PM -0800, ve7gmn wrote:
> I think I might have damaged my unit.When I start the emu it now says write and step active make sure j2 is not backwards or something along those lines , what should I check

ve7gmn

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Feb 1, 2021, 11:02:34 AMFeb 1
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Not a new build , was working then started to output this error. Does it with the cables unplugged or plugged



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David Gesswein

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Feb 1, 2021, 12:58:58 PMFeb 1
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I assume know known change around when you started getting the error.
I assume you have also power cycled the board.

Schematic is here
http://www.pdp8online.com/mfm/board/mfm_revb_pcb/pdf/top.pdf

I assume you have at least a volt meter. The board has a couple marked
ground pads to can use to measure to.

Measure the voltage on the write line U2 16. It should be > 3V.
If not check at RN1 which pulls the signal high. Pin 1 is 3.3V and pin 4 is
the write line.

If that was high check U2-4. If its low check that pin 19 is low which
enables U2.

If its high check on P9-31. If that is high it seems to be a problem
with the beaglebone.

The other signal the error refers to is E_STEP.

ve7gmn

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Feb 2, 2021, 12:16:32 AMFeb 2
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Thanks for the help, it was a cold solder joint pin 1 of rn1,all good now

Thanks





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-------- Original message --------
From: David Gesswein <d...@pdp8online.com>
Date: 2021-02-01 9:58 a.m. (GMT-08:00)
Subject: Re: mfm_emu

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