Author Topic: Pork Barrel 2015 mistake  (Read 1599 times)

madbean

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Pork Barrel 2015 mistake
« on: February 04, 2015, 12:26:07 PM »
Time to eat my hat. I boned a resistor connection on the Pork Barrel 2015. Somewhere in between updating the 2011 board to my 2014 library and modifying the layout I connected R29 to the wrong spot. It should be connected to ground, and the trace should be routed to pin 2 of IC4.

The correction is very easy to make, however. Jumper R29 and then solder the 10k resistor between pins 5 and 4 of IC4 on the bottom of the PCB.

I have updated the project doc with the explanation and a pic of how to make the correction. My apologies for the mistake. Also, I have added in the voltage measurements for the ICs in the doc. These were done for an MN3007 after calibrating the bias trim so it should be a good target for all the variations you can build.

Lastly, while I had it on the bench I tried running my MN3007 at 15v. I was surprised to find that the LFO actually does not work properly at this voltage. It looks like it needs to be tweaked. While I do not have time today to figure that out I will look into and post my findings as I think this is an important feature to have.

Direct link to the updated Pork Barrel doc: http://www.madbeanpedals.com/projects/PorkBarrel/PorkBarrel_2015.pdf
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chordball

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Re: Pork Barrel 2015 mistake
« Reply #1 on: February 05, 2015, 09:08:52 AM »
Is there a difference between the lfo on the 2015 vs older versions? There are lots of build reports with 15v operation and no one has mentioned any problems. I'm lazy and still haven't built mine yet.

juansolo

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Re: Pork Barrel 2015 mistake
« Reply #2 on: February 05, 2015, 11:38:51 AM »
Is there a difference between the lfo on the 2015 vs older versions? There are lots of build reports with 15v operation and no one has mentioned any problems. I'm lazy and still haven't built mine yet.

If it's an old one they're fine at 15v.
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madbean

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Re: Pork Barrel 2015 mistake
« Reply #3 on: February 05, 2015, 11:55:47 AM »
It could just be something screwy with my particular build (which would be weird because it is working perfectly). There is no difference in the LFO's once the resistor mistake is corrected. I've got an older build I can use to compare...I'll look into it soon.
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madbean

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Re: Pork Barrel 2015 mistake
« Reply #4 on: February 05, 2015, 12:11:16 PM »
I think I know what it is - I'm using an old Road Rage board on my testing rig that's got an LM78L15 on it. Under load the PB is pulling down to 13.5v so obviously it is taxing the regulator. I'll try replacing that and see what happens. I've got a benchtop power supply I can use for comparison, too.
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chordball

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Re: Pork Barrel 2015 mistake
« Reply #5 on: February 05, 2015, 01:10:14 PM »
Thanks for the replies. Mine is the 2011 version.