The GrubDAC
Mar 30, 2014 at 3:08 PM Post #1,038 of 1,079

Avro_Arrow

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As far as I can see, despite the soldering job, only pins 1, 2 and 3 on the PCM2706

seem to be problematic. The fact that it is recognized by the computer suggests
that the problem lies with either the I2S lines from the PCM to the WM8524, or
with the WM8524.
 
It looks like your soldering iron is too cold or there is not enough flux.
What kind of solder and soldering iron do you use?
 
Mar 30, 2014 at 4:26 PM Post #1,039 of 1,079

iwuk78

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I'm using a Hakko 936. I think it is the solder. I had thought it was flux core, but I think it's actually not, and I only had a "no clean" flux pen lying around that didn't seem to help a great deal. It's fine for through hole, but I guess surface mount stuff is a little more picky... I really should have waited and got some decent solder (it is also way too thick), but I was a little too eager to get going. I regret that now! Lesson learned.
 
I have re-flowed the WM8524, but still no go. I wonder if I may have fried it. Is there a way to determine that, short of just replacing it?
 
What kind of solder do folks recommend for this kind of work?
 
Thanks for the help.
 
Mar 30, 2014 at 5:06 PM Post #1,040 of 1,079

Avro_Arrow

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This is the solder I use...it's nothing special but it gives me good results:
 
 


I also use Solder Paste for SMD work.
I have my iron set for 500 - 550 F.
 
If you have access to an oscilloscope, you could check that the WM8524
is getting the correct signals, but short of that, replacing it is the next
option.
 
Before you go to that extreme, do a continuity check.
Using the schematic, check that the pins on the PCM are
actually connected to the pins on the WM and aren't shorted
to anything else along the way. You can also check that
the other pins also go to where they should and are not
open or short.
 
Good luck!
 
Mar 30, 2014 at 6:20 PM Post #1,042 of 1,079

iwuk78

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You got it! I checked continuity between the PCM and WM, which was fine. I then checked between the top of the pins on the WM and the pads and found one that was not soldered (looked like it was, even with magnifier). Beeped only when applying pressure. Resoldered it and BAM! Sound! 
 
Thank you for taking the time to look at this, it is much appreciated! 
 
I'm going to go and get ice cream to celebrate haha. 
 
Made my day :)
 
Thanks for the pics too. I think I'll definitely pick up some better solder before attempting any smd work again. The stuff I used needed the iron at about 600f to flow properly.
 
Mar 30, 2014 at 8:03 PM Post #1,043 of 1,079

Avro_Arrow

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  Thank you for taking the time to look at this, it is much appreciated! 
 

 
Your welcome, I hope you enjoy it!
 
Apr 18, 2014 at 11:27 AM Post #1,044 of 1,079

LosNir

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Hi Guys! Another one with a no-sound problem right here!

Here are some notes:

1. The GrubDAC is detected fine by Windows and shows up on playback devices. No instabilities.
2. The LED lights up.
3. 3.3V Test point shows stable ~3.29V.
4. 5V Across C5. 3.3V Across C1 & C15.

I've reflowed U1 and U3 and cleaned the board several times, with no luck.

Any ideas?



Thanks.
 
Apr 18, 2014 at 3:32 PM Post #1,045 of 1,079

Avro_Arrow

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Can you check from ground to pin 2 on the wolfson?

There should be -3.3 volts.
 
As far as I can tell from the pictures, soldering looks good.
 
Apr 18, 2014 at 3:38 PM Post #1,046 of 1,079

LosNir

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I managed to get it working :)

I didn't do anything special actually.
I just took it to take some high-magnification pictures using my USB Microscope, and then I checked for continuity across some of the Wolfson's pins, and then it started working.

It might be the multimeter leads that scrapped of some solder that bridged two pins. :)
 
Jun 10, 2014 at 9:42 PM Post #1,047 of 1,079

vonchap

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I put my GrubDAC inside my Objective 2 (instead of an ODAC) and soldered the line out directly to the O2 board. I would like to add a RCA out from my GrubDAC. Can I simply solder it to the existing line out wires? 
 
Jun 11, 2014 at 10:52 PM Post #1,048 of 1,079

tomb

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  I put my GrubDAC inside my Objective 2 (instead of an ODAC) and soldered the line out directly to the O2 board. I would like to add a RCA out from my GrubDAC. Can I simply solder it to the existing line out wires? 


I think the problem is, will you have both outputs connected to anything at the same time?  I'm not certain about the O2, because it deviates from accepted practice in the location of the volume pot in the circuit.  However, if you connected both outputs to amps whose volume pots are at the input of the amplifier circuit (typical), then the static resistive load of the two pots will reduce the output of the DAC - perhaps to an unacceptable level.  When I say "static," I mean even with the amp off - the resistive load of the volume pot is still there.
 
What you want to do would work better with a switch, I think.  A DPDT switching the signal leads with a shared ground should work.  That way, the DAC only sees one load at a time.
 
Jun 12, 2014 at 7:43 AM Post #1,049 of 1,079

vonchap

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Originally Posted by tomb 
 
What you want to do would work better with a switch, I think.  A DPDT switching the signal leads with a shared ground should work.  That way, the DAC only sees one load at a time.

 


Thank you! I will try that. By the way, I really love the GrubDAC. It works flawlessly for me and sounds great! I A/B it with the ODAC and couldn't hear a difference.
 
Jun 17, 2014 at 9:34 PM Post #1,050 of 1,079

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Hi All,
 
After a few days of fiddling with the GrubDac (Missed a few pins on U1 and U3, needed to reflow a point on X1) I finally got sound. Unfortunately it was super static-y and distorted, like a radio station that's not quite in focus. I noticed there was still a lot of flux on the board, so I scrubbed it down with 91% isopropyl alcohol, plugged it back in, and now no sounds. Sad dude.
 
I get 3.3v at that test point and 5.1v at the 5v point. LED does come on and it is recognized by the computer (Mac OSX). I will post pictures as soon as my account is allowed to do that, but it does not look like i have any bridges on the chips.
 
UPDATE: Just plugged it in again this morning, played beautifully for about 30 seconds, then started to get progressively static-y again and now nothing. Just when I thought there was HOPE!
 
 
Thoughts?

Witold
 

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