Re: [sdiy] Broken fatman

[carsten at analog-monster.de]

Hi Karl,

as I know MIDI IN schemos high value is connected via resistor to the
collector of the final transistor of the optocoupler (pin 6 of 6n138).
An incoming MIDI signal causes a voltage drop at this pin to low
(according to the bits - incoming high (1) meaning low, 0 meaning
high). So permanent low could be the result of:
 - permanent incoming high (pin 2) due to crash
 - 6n138 is in silicon heaven due to crash
 - high value at pin 6 vanished due to crash
and a following indicator indicates a permanent MIDI signal due to 0V at
the output...

Hope this helps

Carsten
-- 
Analog-Monster!
Synthesizer DIY Project
http://www.analog-monster.de

Karl Ekdahl <_nial_ at yahoo.com> schrieb am 27.05.2004, 09:01:21:
> Hi all, a friend of mine bought a fatman two weeks ago
> and dropped it in the floor one week after so now it
> doesn't respond on midi and indicates a constant midi
> input. I've checked the schemo, and as i understand it
> ic6 (the 6n138) pin 6 should be LOW on active signal.
> The signal is LOW all the time, no matter if i've
> connected a midi cord or not, so i'm wondering, do you
> really think that the 6n138 could have braked because
> of the fall? Maybe i'm totally missinterpretating the
> schemo...
> 
> thanks
> 
> karl
> 
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