[sdiy] EFM MIDI-Gate?

[Chromatest J. Pantsmaker]

Ah.. sorry, that was old information and was indeed a problem with the
scope.  I'm using a really nice scope now and I still can't get the
circuit to work.

It seems that I'm not getting any output on the 6n138.  I just get 5V
and it doesn't appear to be pulsing or anything like that.  I've
compared the schematic with the traces, and everything goes where it's
supposed to.

On Wed, Feb 24, 2010 at 6:22 PM, Jerry Gray-Eskue <jerryge at cableone.net> wrote:
>  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
>