The Objective2 (O2) Headphone Amp DIY Project

[sofaspud]

You probably know already, but don't turn on the power button until you have this ps issue resolved.
I'm not seeing anything wrong with your parts installation. Except for Q1 and Q2, which shouldn't have an effect on the regulator circuit. My Q1 PQU17P06 is the DPAK package and Q2 PQPF10N20 is the insulated TO220. Q1 is nearest the regulators and Q2 is nearest the batteries. Yours seems backwards, but you may have sourced different parts. Worth a quick check.
What voltage do you read between the cathode of D3 and the anode of D4? It kinda seems like you're only getting halfwave power. The reading should be around 32 volts with your transformer.

[sofaspud]

It's not possible to tell if the regs are in reverse positions from the photo, but that would definitely give bad outputs. If you can get them out and put in their proper places, they should still be good. They can take a lickin' and keep on tickin'.

[hochopeper]

Cheers guys, will try taking the regs out as a first step.

Cathode D3 measured 16.9V wrt gnd. Anode D4 was -16.9V wrt gnd when I measured them earlier. Which is in the ballpark you indicated and lines up with range indicated by RS in this drawing.


Edit: Just got the first one out. Had the 7812 in U6, that confirms that part of the puzzle!

[Turbon]

@hochopeper...

As sofaspud wrote, check the regs before you solder them back again so that you get the right one at the right position. There are pictures earlier in this thread as there are in RS (nwavguys) blog. So if you have bought parts according to the BOM you could use the pictures to get them right.

Brgds

[sofaspud]

Glad the problem got tracked down. I suggest temporarily soldering some small wires from the PCB regulator input and ground to the respective regulator leads while they are off the board, then measuring the output pin to make sure you get + and - 12 volts. Just to verify they are still functional before permanently replacing them on the board. Please check those FETs too while the iron is hot.

[hochopeper]

Originally Posted by sofaspud

Glad the problem got tracked down. I suggest temporarily soldering some small wires from the PCB regulator input and ground to the respective regulator leads while they are off the board, then measuring the output pin to make sure you get + and - 12 volts. Just to verify they are still functional before permanently replacing them on the board. Please check those FETs too while the iron is hot.

Certainly not as glad as I am! Regulator voltages all check out now.

Thanks for mentioning the FETs too! They did need swapping. But ...

I think Q2 may have not enjoyed the relocation. Have checked the voltages quickly already but I'll try again tomorrow to get to bottom of those. All of the voltages related to Q1 seem ok.

Lesson learned for trying to whip it up in a hurry late last night though!

[fourier]

Hello Guys.. Does anyone here have the latest version of the pcb gerber & drill file (september ver)? I have tried to download the files from nwavguy blog but only got the august version (aug date written on the board)
Thanks in advance for the help!

[RocketScientist]

@hochopeper, I'm glad you found your regulator problem. Be sure to carefully run the power controller tests (removing each battery and following the instructions) to make sure Q1 and Q2 are working correctly.

@fourier, I have not revised the gerber files. The only changes since August have been to the parts list, not the PCB board. The only change I've considered making is to move the via away from the corner of the gain switch. But it doesn't seem to be a problem for the majority of O2 builders and is easily fixed if it is.

[shadow419]

Having a little trouble with my second build. I'm getting nothing for the initial supply voltage test using the wall adapter and measuring across the battery terminals. All I get is a rapidly descending mV reading. I tried re-flowing the power terminals, but that did nothing. I know the voltage regulators are in correctly, although I could try and re-flow those connections as well. Any ideas where I should start?

[RocketScientist]

@shadow, it sounds like perhaps your DMM is set for AC voltage (rather than DC), you're not connecting one probe to a proper ground, there's a short on the board between the power jack and the regulators, or your wall transformer is toast.

Measure, with the DMM set for AC, the voltage at the wall adapter plug (without it even plugged into the O2). It should be 13.5 volts AC or more. If it's zero you found your problem. If that's OK, plug it into the O2, switch your DMM to DC, and measure at the diodes near the power jack as shown in the diagrams on the blog. You can also measure across any of the 4 big power supply capacitors. Each should be 16+ volts DC.