Optocoupler replacement

Uncle Krunkus

Hey everybody,
I've got a Boss AutoWah in for repairs, and the optocoupler is reading as a dead LED on one side trying to drive an open circuit LDR on the other! Rolling Eyes

So I think it's got a snowflakes hope in hell of working the way it was supposed to. Laughing

It's a HTV P873A, and I was wondering if anyone knows what the specs for it are, as I haven't been able to find them anywhere. I haven't actually got any Vactrols but I'm hoping, if I can get some specs, I might be able to roll my own equivalent to get it running again.
Thanks heaps for any advice in advance!

ryktnk · Posted: Fri Jun 27, 2008 3:07 am Post subject:

Hello

This is the company that made them
http://jp.hamamatsu.com/en/index.html

You could try emailing if they still have some documents.

Also here is a graph of test results that Mr RJB did with the
HTV-P873-G35-380, which might be similar . . .
http://homepage2.nifty.com/rjb/diy_synthe12.htm

-ryktnk

HTV-P873-G35-380.jpg

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Uncle Krunkus · Posted: Fri Jun 27, 2008 4:04 am Post subject:

Thanks heaps ryktnk!
That's all I needed, just a ballpark figure on the dark resistance. So I'm looking at about 100K.
In fact the pic on that web page has an almost exact copy on it. (The one at the bottom) So I can be fairly confident about what the original was doing.
Thanks again,
Andrew

Uncle Krunkus · Posted: Fri Jun 27, 2008 6:00 am Post subject:

I just dropped one of my hand rolled Vactrols in there and now it's wahing away quite happily!

Pierre · Joined: Feb 24, 2009 Posts: 9 Location: France

Hello,

What model of Vactrols optocoupler do you used? A VTL 5C1?

Pierre

Uncle Krunkus · Posted: Tue Mar 03, 2009 2:26 pm Post subject:

I made my own

Pierre · Joined: Feb 24, 2009 Posts: 9 Location: France

Oh my god!!!!!!! Shocked

And how do you do that?

Can you teach me?

I'm just a newbie....

Crying or Very sad

Thanks

Pierre

Uncle Krunkus · Posted: Tue Mar 10, 2009 8:24 pm Post subject:

Get a small piece of aluminium tube with an inside diameter of 5mm.
In one end you put a relatively high brightness 5mm LED, yellow works best, (experiment).
In the other end (after flattening one side of the tube) you should be able to fit an LDR. One with an on resistance of less than 5K would be best. (again you might need to try a couple to find the best type)
Then I put some small heatshrink on the leads, and put a larger piece of black heatshrink right over the top of it all.

Pierre · Joined: Feb 24, 2009 Posts: 9 Location: France

Thanks Uncle Krunkus.

I'll try it!

Pierre

Laughing