[Build] CAPI HPA500, 500 Series Headphone Amplifier, Official Support Thread

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jsteiger

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At first quick glance, the LED leads seem pretty look and appear to be hanging off of the back of the solder pads. They can short to the ground plane so I would correct that.

You can check the right end of the 330R's to make sure the receiver is passing both left and right.

Might be silly to ask but have you swapped the XLR inputs at the back of the rack to make sure its not an external wiring thing?
 

rockprocess

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Thanks, I’ll trim those leds.  I’ve swapped cables externally, swapped the opamps.  I’ve put two different test tones going into the unit on both channels so that I can tell if I hear the left side.  No luck on the left.

I’ve got no signal at r27 but full signal at r28.
 

jsteiger

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rockprocess said:
Thanks, I’ll trim those leds.  I’ve swapped cables externally, swapped the opamps.  I’ve put two different test tones going into the unit on both channels so that I can tell if I hear the left side.  No luck on the left.

I’ve got no signal at r27 but full signal at r28.
R27 and R28 immediately follow the OPA2134 receiver amp. Test on their right ends closest to the OPA2134.

I would look for a cold solder joint or miss placed R with the following:
R30
R36-R40
C22
C26
C29-C30
 

jsteiger

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rockprocess said:
Great advice Jeff.  I got it working.  Great sounding module!!!
Awesome!

What was it? Maybe it'll help someone in the future if you share what the issue was.
 

rockprocess

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Thanks Jeff.  I’m embarrassed to say it was my fault, not the module.  I plugged one side into the extra jacks on my api 500 lunchbox.  I hadn’t used the far right side slots yet where the pass through jacks are.  Please excuse my stupidity!
 

nicholasdover

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Hi guys

I made an initial mistake in a hurried and poorly lit build situation and put the wrong IC in A3, then when I corrected it, only one channel was working.  I switched A1 and A2 around, but no change so presumed I'd damaged A3. I just got a new IC for A3 through the mail and everything worked perfectly for a couple of minutes, but now one side has gone down again, and A1/A2 switch isn't curing it. So it seems my build is blowing one channel of A3 - is that possible? What could deliver a damaging blow to the IC? I did plug in and out of the extension jig without power down ( it was the only module in the rack, no power button, impatient, reckless...) so is there possible harm from "hot switching" like that?
Thanks
Nick
 

jsteiger

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Hot swapping should not be an issue. It could also be bad solder joints somewhere. I mentioned in a post above where to check for audio immediately after the receiver chip. I think other folks have had trouble with faulty solder joints where the 2 boards connect.
 

nicholasdover

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I'll check the solder joints tomorrow, but that side of things was neat I think and it did work fine for that couple of minutes. I made a mistake with the transistors too which is rectified now but I guess they could have been harmed? They weren't reversed in slots or anything, but 2 were in wrong positions. It's embarrassing... I have my reasons....
I can get hold of the IC's and transistors here (UK) if necessary but they're not cheap so it'd be good to know I'm replacing the right things if it comes to that.
Couple of new A3 IC's coming tmrw so I'll see if same thing happens.
 

radtunez

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Hi Jeff,

I am a bit puzzled, as I thought this build was a breeze, but alas, my HPA is not functioning. At the moment, I am only getting Left channel signal and even that is very low. The pot is very scratchy and ceases to function after 3 o'clock. I have double checked all my placement, but I attached a photo just in case. I checked all joints and carefully redid any that were remotely suspect. I also cleaned the PCB well. The only issue that I am wondering about is there is a bit of daylight between the shroud and the ALP PCB on JP3. But the pins are not touching the L bracket beneath. I redid and cleaned the joints to the main PCB, and the soldering of pins to the ALP pcb look good to me. What am I missing?

Thank you so much,
Ryan
 

radtunez

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radtunez said:
Hi Jeff,

I am a bit puzzled, as I thought this build was a breeze, but alas, my HPA is not functioning. At the moment, I am only getting Left channel signal and even that is very low. The pot is very scratchy and ceases to function after 3 o'clock. I have double checked all my placement, but I attached a photo just in case. I checked all joints and carefully redid any that were remotely suspect. I also cleaned the PCB well. The only issue that I am wondering about is there is a bit of daylight between the shroud and the ALP PCB on JP3. But the pins are not touching the L bracket beneath. I redid and cleaned the joints to the main PCB, and the soldering of pins to the ALP pcb look good to me. What am I missing?

Thank you so much,
Ryan
 

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