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jamesbythebay 5th November 2013 08:21 AM

Amp Camp Amp...built it, but no power. Need help troubleshooting!
Hi all,
I finished my slow...meticulous..assembly of the ACA kits. Everything is double and triple checked for proper parts placement and polarity. The switches and power supply inputs appear to be wired correctly.

I flip the on/off switch. No light. Less than one vac between Q1 and ground. When power is switched off, vac at power connection measures 10.25v.

Both amps measure the same. I've tried both power supplies. Same results.

Any thoughts on troubleshooting?


Zen Mod 5th November 2013 10:26 AM

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Bones13 5th November 2013 11:34 AM

I agree with pictures needed. The PSU (laptop power bricks) output DC only. I'm no expert, but I can make mine look like pictures here. Be sure the right transistors are in the right place, and cap polarity is correct. Get a DC volt measure of the power at the jack, switch, and at the power in spots on the boards.

jamesbythebay 5th November 2013 07:02 PM

Hey Bones & Zen,
Thank you so much for reading and replying to my really late night post! After getting a bit of sleep and thinking on Bones reminder that the PS was outputting VDC (thank you!!!) and not VAC, and that I was having the exact same set of symptoms with both amps, I pulled out the 'ol Fluke, made a couple of voltage measurements and then fixed the problem.

The failure to power up problem was caused by not connecting the ground lead (from the board) to the proper pin on the power jack. There are three blades. The center pin is positive DC. Clockwise, as one looks at the pin side of the jack, the next blade is negative DC. The third blade, again clockwise, is unused. The diyaudio ACA build guide states "Solder a black wire from the point marked GND to either of the remaining tabs on the power jack." I did this, and got unlucky enough to choose an unpowered blade on the power jack. Two lead swaps later, I was measuring 10VDC at Q1/GND. Yay!

I measured every single part for continuity, specs and polarity...except the power connector.

It's always that last one that gets you...

Right now these two little cuties are baking away on the bench. The voltage is slowly drifting upward. Life seems to be righting itself...

Thanks again guys.

Bones13 5th November 2013 08:44 PM

I will admit that I spent a lot of time inspecting the blades on the power jack before installing/soldering anything.

Zen Mod 5th November 2013 09:47 PM


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