Analogue-sequencer

In-Reply-To: <bvqrtd+2pfp@eGroups.com>
Cheers Colin you are a star!



Keith

http://home.freeuk.net/lowpass

On 4 Feb 2004 at 16:06, keithw@cix.compulink.co.uk wrote:

> In-Reply-To: <bvqrtd+2pfp@eGroups.com>
> Cheers Colin you are a star!

Does that mean you found the problem then keith

What was it?

Andy
---

Andy Wilson
http://www.techman.synth.net
andy@techman.synth.net

Folks,

I've been having a look at the occasional problems of non-
functioning 6N139 opto-isolators, and come to the conclusion that 
the resistor values specified up until now are not suitable in 100% 
of cases.
I know Andy had a problem with one, I suspect Keith's upgrade 
problems are caused by it, and I've got a new ready-built unit here 
that was exhibiting the same thing.
The values I use are based on a reference in a book I've had for 
years, although I've increased the load resistor myself when I've 
had trouble before.
I had a look at all the midi input circuits based on 6N139s I could 
find on the web today, and there seems to be no consensus at all as 
to what they should be. The datasheets for the part are pretty vague.

So, if you find you get BAD DATA warnings while flashing, first try 
removing R3. If that doesn't work, try replacing R3 with 10k.

> So, if you find you get BAD DATA warnings while flashing, first 
try 
> removing R3. If that doesn't work, try replacing R3 with 10k.

...godamit Yahoo, I wasn't finished... 

If messing with R3 still doesn't get you going, try a lower value of 
R2 - e.g. 680R.

I'll continue to poke around and see if I can come up with a 
definitive set of values for this.

Cheers,
Colin f