[sdiy] EFM MIDI-Gate?

[Jerry Gray-Eskue]

 Pins 5, 6, 7, and 8 all show the same
> waveform which doesn't seem right to me at all.

According to the schematic You should have +5v on 8 and Ground on 5.
Check your power supply, and be suspicious of your o-scope software, as
several people recently pointed out the sound card inputs are usually AC
coupled and so cannot see DC voltages.

Use a Voltmeter or DVM (if you have one) to check out the DC voltages.

Also the Input side of the opto should have a floating ground relative to
the rest of the circuit.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Chromatest J.
Pantsmaker
Sent: Wednesday, February 24, 2010 5:52 PM
To: Dave Kendall
Cc: Synth DIY
Subject: Re: [sdiy] EFM MIDI-Gate?


I'm still working on this thing, haven't figured out what's wrong yet.

I bought a stack of 10 6n138 optocouplers from mouser.  I've tried
several now with the same results each time.  I'm wearing a ground
strap.

So, using the scope, I'm seeing 5V data bouncing on the inputs of the
6n138 (pins 2 and 3) but on the output, I'm just getting a slightly
fuzzy +V and the scope says that it's detecting DC voltage on that
pin.

I've pulled out every other IC (all socketed) and the results are the same.

Thoughts?

The Schematic is here:
http://chromatest.net/EFMmidi-gate.pdf

On Fri, Nov 13, 2009 at 8:47 AM, Chromatest J. Pantsmaker
<chromatest at azburners.org> wrote:
> I think I may have a dead optocoupler, so I'm gonna buy some
> replacements and see if that helps.  I'm not really sure how to check
> the one I have.  I'm using the o-scope software (freeware) that uses
> your soundcard as an interface.  Pins 5, 6, 7, and 8 all show the same
> waveform which doesn't seem right to me at all.
>
> On Fri, Nov 13, 2009 at 7:16 AM, Dave Kendall <davekendall at ntlworld.com>
wrote:
>> Hi.
>>
>> FWIW, I stuffed the board years ago, but never tested it. However I made
a
>> couple of notes when examining the circuit traces.
>>
>> Silkscreen error:  +5V and GND down near the 7805 voltage regulator are
>> incorrectly swapped over. +5V should be nearest the edge of the board.
>> It works, but the silkscreen is wrong..... (batch number H&L - 1 5100)
>>
>> D1 should be jumpered. LED is not used. (don't know why - I think I got
that
>> from Tom G's notes some time....) The pad nearest to the legend J1 is
>> ground, the pad connected to junction of D1 and R1 is +15V or +12V.
>>
>> C2 is a 10uF electro (25V ). The negative is connected to GND, ie. facing
in
>> towards R8. (did I sub the ceramic caps? Hmmmm)
>>
>> I haven't got the board in front of me, so can't check exactly why I
wrote
>> this stuff.
>>
>> Hope this helps anyway...
>>
>> cheers,
>> Dave
>>
>>
>>
>> On Nov 12, 2009, at 06:08, Chromatest J. Pantsmaker wrote:
>>
>>> So, I'm starting to revisit some old projects... The first of which is
>>> the EFM MIDI-Gate interface.
>>>
>>> I have one built, but at the time when I built it, I couldn't get it
>>> to work.  That was roughly in 2000 or so.
>>>
>>> I have the original PDF file, but as I remember, there were often
>>> extensive re-work notes for each EFM board produced.
>>>
>>> Does anybody have those notes?
>>>
>>> Does anybody have a working MIDI-gate who could help me troubleshoot
mine?
>>>
>>> --
>>> .sig
>>> -Chromatest J. Pantsmaker
>>> http://www.chromatest.net
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
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>>
>
>
>
> --
> .sig
> -Chromatest J. Pantsmaker
> http://www.chromatest.net
>



--
.sig
-Chromatest J. Pantsmaker
http://www.chromatest.net

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