From: William Levak (wlevak_at_cyberspace.org)
Date: 2002-11-11 04:24:08
On Sun, 10 Nov 2002, Marko [iso-8859-1] Mäkelä wrote:
> Tapeconnector Port I (backplane) Port II (inside)
> Signal/Pin connected was connected was
> ------------------ TAP ---- C2N232-----TAP----C2N232
> Sense 6-F +2V +3,5V +4,5V +5V
> Write 5-E +5V +5V +5V +5V
> Read 4-D 0V +5V 0V +5V !!!!!!!
> Motor 3-C 0V +7,5V 0V +0V
> ###
> Vcc 2-B +5V +5V +5V +5V
> GND 1-A GND GND GND GND
The sense line on port I is too low. This line goes to PA4 on the 6520.
This is a TTL level signal and should be close to either 0 or 5 V.
Anything else indicates a problem.
It could be the jumpers for selecting the port configuration. They are
located just behind the keyboard connector and should be connected front
to rear for the configuration above.
The 6520 could also be defective.
There could also be a short on the circuit traces. I once found a fine
solder thread between 2 circuit traces on a casette port. It was so
fine it took a magnifying glass to find it. It was under the green
varnish they coat the board with, so it was a manufacturing defect.
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