Madbean phase 45 stalled again...

Luke51411 · March 30, 2014, 08:35:06 PM

So this is the second time I don't have something in my inventory to complete the build. How important is the value of r19, I don't have a 3m9 resistor can I replace it with something else? Also I have the tayda 2n5457 fets of which I have found a matched pair. Should these work? I know I've heard of issues with fets from tayda before. Thanks for the help.

vigilante397 · March 30, 2014, 11:08:33 PM

I've never had any issues with FETs (or anything else for that matter) from Tayda, but when you don't feel confident about a component then make sure to socket it in case it doesn't work out.

As for the resistor, when I don't have access to a part my first choice is always something within the 10% tolerance range, and if I can't find anything there then my second choice is running multiple components together. In this case you would need to run multiple lower-value resistors together to add up to 3.9 M or thereabouts. This could be a pair of 1.9M, 2M, etc. or four 1M if you're really desperate

Good luck

deadastronaut · March 31, 2014, 05:16:55 AM

i presume the 3.9M is for depth. go high. i stuck a 4.7M in mine..

Luke51411 · March 31, 2014, 07:21:34 AM

Ok thanks I'll try that and fire it up tonight!

Luke51411 · March 31, 2014, 07:41:59 AM

Oops I meant to post a link to the build doc, just realized I didn't. I think my question was answered anyway. Thanks.

Kipper4 · March 31, 2014, 10:29:27 AM

this one
http://www.madbeanpedals.com/projects/Smoothie/Smoothie.pdf

Luke51411 · March 31, 2014, 10:54:07 AM

Yeah that's the one.

Kipper4 · March 31, 2014, 11:00:29 AM

have you got and resistors you can put in series or parrallel to make the 3k9. as someone suggested earlier?

Luke51411 · March 31, 2014, 11:06:15 AM

I have 2m2 and 4m7. I ordered some 3m9 resistors so I'll probably just wait since it is on a pcb and there isn't much real estate.

Kipper4 · March 31, 2014, 11:22:22 AM

id just tack that 4m7 in and see as Dead Astro suggested

Luke51411 · April 01, 2014, 09:33:45 PM

I got the p45 built and working with a couple hitches. The trimpot isn't smooth and wouldn't go past half until I forced it. I wonder if the cheap tayda 250k trim pots are actually 500k limited to half the travel.
My 2n5457s are matched within .002. I know this is a pretty subtle effect but would there be more phase if they were matched closer than that? I only get noticeable phase shift at 3/4 to the end of the pot travel though I think part of it is that I can't dial in the trimpot very good. I will switch out the trimpot tomorrow to see if I can get more range.

jimilee · April 02, 2014, 12:25:26 AM

Quote from: Luke51411 on April 01, 2014, 09:33:45 PM

My 2n5457s are matched within .002. I know this is a pretty subtle effect but would there be more phase if they were matched closer than that? I only get noticeable phase shift at 3/4 to the end of the pot travel though I think part of it is that I can't dial in the trimpot very good. I will switch out the trimpot tomorrow to see if I can get more range.

Mine sounds the way you've described also. May be normal.

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Madbean phase 45 stalled again...