[HELP] Arion Sad-1 Problem

HeaD · September 16, 2006, 09:54:48 AM

Hi all,

I've a problem with a SAD-1 of mine (I got 2). When I stomp, the LED light on but the effect does not work, the sound is unaltered. I've done a search and have found a post with the same problem, there is also the schematics:

http://www.diystompboxes.com/smfforum/index.php?topic=44923.0

Initially, I've also thought to the flipflop/fet, but I've checked ALL pins voltages, and are the same of the other pedal.

I don't understand... does someone have any ideas? Thanks.

Paul Marossy · September 16, 2006, 10:47:23 AM

How are you powering it?

HeaD · September 16, 2006, 01:14:18 PM

Hmm, I don't think that this is a power problem. I've tried with a power supply and with a 9V battery. (The other sad-1 works with both)

Any other ideas? Thanks

Paul Marossy · September 16, 2006, 01:41:59 PM

Hmm... OK. Are there any electrolytic caps that look like they might be leaking? It sounds to me like your flip-flop circuit isn't flip-flopping...

HeaD · September 16, 2006, 01:55:16 PM

externally, elec. caps seems ok... anyways I will replace them...

HeaD · September 16, 2006, 04:07:28 PM

Hey Paul,

I've tried to replace the 0.47 electrolytic caps around the fet (you're talking about them?), but nothing... Can the problem depend on the delay chip or something?

Paul Marossy · September 16, 2006, 04:14:25 PM

Might be a bad delay chip - possibly. I would suggest feeding the circuit with an audio oscillator and using an audio probe to see where the signal stops. If it stops right the flip-flop, then maybe one of those devices is bad. If it makes it past there, then the problem is elsewhere.

HeaD · September 16, 2006, 06:21:39 PM

I've replaced the MN3205 with the one of the other SAD-1, and it works.... but now the "repeat" control seems to work strangely.

If I turn the "repeat" control all the way up, repeats are not infinites.... what can it be? Thanks again..

Paul Marossy · September 16, 2006, 10:28:06 PM

I'm not sure. I'm out of ideas for the moment.

While you're at it, you might want to socket whatever chips you pull out.

HeaD · September 17, 2006, 05:38:42 AM

Yeah, I'll do it

Could the amount of repeats depends on the two trimpots? Or maybe the MN3102? Thanks Paul

Paul Marossy · September 17, 2006, 09:17:26 AM

Well, the trimpots may have something to do with it. The 100K trimpot with the wiper connected thru a 100K resistor to Pin 7 of the MN3205 sets the bias. The other 100K trimpot connected to Pins 3 & 4 of the MN3205 appears to be some kind of balance pot. That's probably where I would start since that is associated with the Repeats control thru that UPC1571C chip.

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[HELP] Arion Sad-1 Problem