The GrubDAC
Jun 18, 2014 at 12:31 PM Post #1,051 of 1,079

tomb

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1. You assembled it correctly. The fact that you got sounds at different points proves that.

2. You still have some dodgy soldering joints somewhere, most likely on the usb or dac chip. The fact that it works, doesn't work, or has static and pops all confirm this.
 
Jun 18, 2014 at 12:48 PM Post #1,052 of 1,079

WK3K

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Thanks Tom. I guess the project for this evening will be reflowing the chips. I haven't messed with the mini-USB either, so I'll give that a go. Again, I'll get some pictures up as soon as my account is allowed access for that.
 
Edit: I tried reflowing U1 and U3 again. It started out playing a little more consistently, but still like a radio stuck between stations. I also have no volume control at the source and the volume seems to fluctuate up and down. Pushing gently on the wolfson chip with my finger while it's playing stops everything completely. It will also just stop playing on it's own after 30 seconds to a minute. 
 
I still see no bridges and have tried resoldering all the pins, so I really don't know what else to try at this point. Just to be safe I've also reflowed everything else. No change.
 
Best,

Witold
 
Jun 18, 2014 at 3:57 PM Post #1,053 of 1,079

WK3K

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Just saw this in the PupDac build notes:
 
"One thing to be aware of - the latest chips from TI use a different case material and is actually hygroscopic.  The pins are sealed at the case body, but the body itself may absorb moisture.  This is nothing to worry about except when you've rinsed at the end and you're ready to plug it in - don't.  Wait for a few hours, use a hair dryer, put the PCB out in the sun, etc. to make certain that things are dry under and inside the chips.  Otherwise, you'll drive yourself crazy trying to figure out why your DAC doesn't work or seems to de-activate itself every few minutes.
wink.gif
"
 
Will that apply to GrubDac components as well? 
 
Jun 20, 2014 at 7:54 AM Post #1,054 of 1,079

tomb

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  Just saw this in the PupDac build notes:
 
"One thing to be aware of - the latest chips from TI use a different case material and is actually hygroscopic.  The pins are sealed at the case body, but the body itself may absorb moisture.  This is nothing to worry about except when you've rinsed at the end and you're ready to plug it in - don't.  Wait for a few hours, use a hair dryer, put the PCB out in the sun, etc. to make certain that things are dry under and inside the chips.  Otherwise, you'll drive yourself crazy trying to figure out why your DAC doesn't work or seems to de-activate itself every few minutes.
wink.gif
"
 
Will that apply to GrubDac components as well? 


It's possible.  There's certainly something going on with the DAC chip if it stops playing when pressed.  Unlike most scenarios, where pressing might put a dodgy connection into good contact, perhaps there's a bridge underneath the chip and/or pins that comes into contact when pressed.  The fact that the analog volume goes up and down, stops on its own, etc. is also an indication.
 
The DAC chip on the GrubDAC is fairly close to an SOIC opamp in terms of difficulty.  Perhaps it can be removed, the PCB cleaned up, then soldered again.  The Wolfson DAC on the GrubDAC is pretty cheap, too - so a full replacement is not a lot of trouble, either.
 
Jun 20, 2014 at 10:43 AM Post #1,055 of 1,079

WK3K

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Thanks TomB. I'll try to remove it and clean everything up over the weekend. I'll be in contact with you about order a new chip as well. 
 
Any tips for removing the chip? Just flood a whole side with solder, heat it up, and pry with an exacto knife?
 
W
 
Jun 21, 2014 at 4:07 PM Post #1,057 of 1,079

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Hi all,
 
I'm having trouble with getting my GrubDAC working. It's recognized by my computer and the test points are good. There doesn't appear to be any bridges between pins. I'm not getting sound though.
 
I've tested for bridges at all the pins, I've tested continuity between the Wolfson and the PCM, and various other points and they all seem fine. I do have a second working GrubDAC and compared the two and haven't found any differences. Any other suggestions on what I can test? Is there a way to test whether the Wolfson is burned out or not?
 
Thanks
 
Jun 22, 2014 at 7:29 AM Post #1,058 of 1,079

tomb

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  Hi all,
 
I'm having trouble with getting my GrubDAC working. It's recognized by my computer and the test points are good. There doesn't appear to be any bridges between pins. I'm not getting sound though.
 
I've tested for bridges at all the pins, I've tested continuity between the Wolfson and the PCM, and various other points and they all seem fine. I do have a second working GrubDAC and compared the two and haven't found any differences. Any other suggestions on what I can test? Is there a way to test whether the Wolfson is burned out or not?
 
Thanks


I would try re-flowing the DAC chip and see if it makes any difference.  If your PC recognizes the GrubDAC and the test points are fine, then the problem is with the DAC chip or your output connections.
 
Jun 23, 2014 at 8:59 PM Post #1,059 of 1,079

triple-u

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I would try re-flowing the DAC chip and see if it makes any difference.  If your PC recognizes the GrubDAC and the test points are fine, then the problem is with the DAC chip or your output connections.

I tried re-flowing the chip and it didn't work. Thought maybe there wasn't enough solder so I tried re-flowing a second time. Stupid mistake. Ended up bridging a few pins and couldn't clean it up. Used solder wick and after an hour struggling with it burned the PCB and destroyed the pins. Don't think it's recoverable now.
 
Oh well...
 
Jun 24, 2014 at 8:14 AM Post #1,060 of 1,079

tomb

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I would try re-flowing the DAC chip and see if it makes any difference.  If your PC recognizes the GrubDAC and the test points are fine, then the problem is with the DAC chip or your output connections.

I tried re-flowing the chip and it didn't work. Thought maybe there wasn't enough solder so I tried re-flowing a second time. Stupid mistake. Ended up bridging a few pins and couldn't clean it up. Used solder wick and after an hour struggling with it burned the PCB and destroyed the pins. Don't think it's recoverable now.
 
Oh well...


If you burned the PCB, then most likely your iron is too hot and the chip was damaged from the first soldering.
 
Send me your address (or confirm it) and I'll send you another Wolfson chip.
 
Jun 25, 2014 at 5:34 PM Post #1,061 of 1,079

triple-u

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If you burned the PCB, then most likely your iron is too hot and the chip was damaged from the first soldering.
 
Send me your address (or confirm it) and I'll send you another Wolfson chip.

Thanks for the offer, but I checked closely and a couple of the pads were also knocked off the PCB. It's going to be a much tougher job. It might be better to start over from scratch. I did order an extra kit, because I was expecting myself to make mistakes my first time soldering surface mounts.
 
Jun 25, 2014 at 10:13 PM Post #1,062 of 1,079

tomb

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If you burned the PCB, then most likely your iron is too hot and the chip was damaged from the first soldering.
 
Send me your address (or confirm it) and I'll send you another Wolfson chip.

Thanks for the offer, but I checked closely and a couple of the pads were also knocked off the PCB. It's going to be a much tougher job. It might be better to start over from scratch. I did order an extra kit, because I was expecting myself to make mistakes my first time soldering surface mounts.


Sorry to hear that.  Let us know how we can help with the next one.
 
Jul 21, 2014 at 2:16 PM Post #1,063 of 1,079

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i just built my first grubdac with a pcm2707 - but the windows 7 main volume control doesn't work. I use this a lot so it is a big inconvenience. I realise that I could simply change the individual application volume control but I prefer having a working master volume control.
 
I checked TI's website and realised that there are newer variants of the chip - PCM2706C and PCM2707. I am considering desoldering the chip and changing to PCM2706/7C - will this solve the volume control issue?
 
Jul 21, 2014 at 2:21 PM Post #1,064 of 1,079

tomb

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It should, but you may be blazing the trail, first. Let us know if it works.

Just to be clear - the problem is with Microsoft's Windows 7, not TI. At least TI developed an entirely new chip revision to try and fix it.
 
Jul 21, 2014 at 2:35 PM Post #1,065 of 1,079

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I am confused about this issue though - I read the documents for the "C" revision of the PCM2706/7 and it seems like they only changed the behaviour of the volume control (i.e. how the volume changes with the win7 volume slider); the "C" variant doesn't seem to enable the volume control. 
 
The document is here: http://www.ti.com/lit/an/sbfa019/sbfa019.pdf
 
I'm trying to isolate the problem: is my non-functioning master volume control due to me using PCM2707 instead of PCM2706, or is it because I'm using the non-C revision?
 
Desoldering and resoldering the IC chip will be a nasty job...
 

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