[sdiy] Matrix 6R MIDI input prob

[harry]

(this is not sarcasm...)

Do you have a scope ?

You can look across the input LED of the optocoupler and you should see
midi data at about 2 Volts... if it is higher the LED might be blown. Then look at
the output side for the same data... maybe inverted but there. Now it should be logic
level, usually 5V.

H^) harry

edanderson wrote:

> I've been hacking around with this dead-to-MIDI Matrix 6R for a bit now.  The problem seems to be in the MIDI input circuit- as seen in the lower right corner of this schem:
>
> http://people.atl.mediaone.net/gail2001/m6proc3.jpg
>
> Since the MIDI thru feeds off of the input "pre-amp" (not sure what it is- opto isolator??) and thru doesn't work, I'm thinkin that the problem lies there.  The schem *seems* to indicate one of two choices here; I've got a PC900V.
>
> Can anyone recommend what sort of tests I could do to pinpoint the source of the trouble?
>
> Thanks muchly.
>
> Ed Anderson