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PostPosted: Wed Jun 26, 2013 7:11 pm 
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Joined: Wed Jun 26, 2013 6:58 pm
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I was quite happy to get my ParaEQ built and running with no major problems. It sounded great.

While powered from a OneSpot, I unplugged another pedal that was connected to the OneSpot.

Since then, the ParaEQ only emits crazy full-voltage oscillations that change in interesting but totally broken ways when I turn the knob. Behavior is the same under battery or adapter.

I would guess that unplugging the device caused a short, spike, or worse in the power supply. No visible damage inside the unit. Nothing hot to the touch.

I would further guess that my best recourse is to swap out the IC's one by one... does anybody have any better advice? ??

The rest of the pedals on my board were unfazed by this event, whatever it was.

Thanks,
jhno


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PostPosted: Mon Jul 08, 2013 1:19 pm 
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Location: Albany, NY
I'd start by looking at the pin voltages on the 1044 charge pump at the top of the PCB. You should see +9VDC at pin 8 and -9VDC at pin 5. If that looks OK, check the voltages on the other IC's as per the schematic in the instructions.

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PostPosted: Mon Jul 22, 2013 2:54 pm 
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Joined: Wed Jun 26, 2013 6:58 pm
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Thank you for this advice! In fact, this was exactly the problem.

The MAX1044 showed +9v from pin 3 to pin 1 or 8, but +0.66v from pin 3 to pin 5.

This suggests to me that the charge pump was destroyed by a voltage spike from the shared power adapter. I found indication on other discussion boards that this part number can be quite sensitive:

http://www.diystompboxes.com/smfforum/i ... ic=97418.0

e.g.,
>The MAX1044 is *almost* an incredibly good part, with one big problem in today's pedal market.
>Your problem is almost certainly the fact that the 1044 has an absolute maximum input voltage of
>10.000000V Above that, they die.

Anyway, I replaced the MAX1044 and my pedal works fine!

Thanks again,
jhno


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