[c12mech]

One thing I learned from the first board was that the two dac chips were a pain.  I must have re-flowed them 4-5 times before I got it to work.  I also found that a decent pair of curved jewelers tweezers are your best friend when dealing with the 0805 parts.  That and a good magnifying lamp.  
 
I'm with forsakenrider, take a break from it for a couple of days and then come back.  I did the same thing and it all seemed to work just right after that. 

 

[Mullet]

That's what's so weird about this. I'm within most others limits as far as iron temps go. I'll have to look up the recommended heat for ChipQuik. This is not the first time I've lifted pads at 600 degrees. Got a new PCM1794 today, so we'll see what materializes. Just in case if I have to jump pin 21 on U1, where does it go to?

 

[Avro_Arrow]

The solder paste I have melts at 361°F (183°C).

 

[tomb]

Not to be contrary, but everyone's methods seem to differ a bit.  I set my iron (Hakko 936) to 650 deg.F., but I'm using a 0.8mm chisel tip and ... my Hakko is getting pretty long-in-the-tooth, now.  I don't think it gets as hot as it used to.  I'm the opposite of cobaltmute on the 805/1206 caps and resistors, too.  I prefer to "prime" the non-ground pad.  I figure the first pad is the one where I've got both hands going with the solder iron in one and tweezers and the chip in the other.  The last thing I want to worry about in that position is whether I can melt the solder.  Better to get the thing soldered down - then you have all day to melt the solder on the other pad.  That goes for the PCM chips, too - I never pick a ground pin as the "anchor" pin.  I messed up an entire PCB this time, though, so maybe I'm doing it wrong.

 
P.S. I never do flood and suck, either.  Seems to me you're daring the solder not to go behind the pins.  If it does, all you end up doing is sucking all the top surface solder that's holding the pins to the pads - before you ever get to the stuff underneath.  I dab a bit at a time on the solder iron tip, then move down the row of pins as long as it looks like there's still liquid solder.  If not, then I put some more on the iron tip.  Once I think there's solder on all the pins, then I "clean up" with a lot of drag-and-wipe's.

 

[Avro_Arrow]

I looked on the website of the manufacturer of the solder I use and
they recommend a temperature of 650 - 700 F.
 
The method of rework soldering they taught at Flextronics when I worked there
was very similar to the method TomB uses.
With the right temperature, solder and flux, you can drag a little ball of solder
down the pins of the chip and it will merrily bounce along from pin to pin leaving
them perfectly filled with no solder bridges between pins. I was able to do it
at work, but I am out of practice and don't have the correct combination so
I can't do it at home reliably.

 

[jdkJake]

I am in the ~650 deg.F camp myself with my 936. I only go above that when I am soldering heat sinks of something that takes away large amounts of heat.

So far, I have never lifted a pad (knocks on wood).

 

[Mullet]

So the plot thickens even further...
 
First I fixed the PCM2707. I needed to use a super small clipping off a lead to bridge pin 21 to its via. Then, I proceeded to successfully replace the DAC chip. I have music again but still have the pulsating sound. So then I decide its time to replace U9 -- the opa2835. Still getting the pulsating sound. I check all resistors and caps to make sure everything looks nice and soldered with no bridges. Also, check to see that I have correct resistors in place. Everything is cool. So then I'm thinking to myself is the opamp oscillating? Is this the noise I'm hearing? I happen to have a spare OPA2365 from a Gamma2 build that I recently had to fix. Lo and behold after replacing the opamp no more pulsating. Music sounds fine. Is this opamp within spec? I think I'm keeping it on there unless there is a more suitable replacement.

 

[cobaltmute]

The OPA2365 should work. I would try the LMH6643 as a chip as the specs are a bit better for this application.

While tomb and I didn't have issue with the OPA2835, and tomb thought it was good, it doesn't surprise me that it may oscillate. With the ground plane right under the chip, the layout is super ideal for the high speed op-amp. I will admit leaving the ground plane under the op-amp was a mistake I did on the proto.

 

[ostewart]

When are kits going to be available and price? As ive been looking for a cheap diy DAC, was thinking of the grub DAC

 

[cobaltmute]

If you have never done SMT soldering before, do a grubDAC first. The pupDAC is not a good first SMT project unless you have *a lot* of patience and are will to spend time checking each part as it goes down.

The kits will be ready when they are ready. Like everything else about this particular project, it is taking time.

 

[ostewart]

Thanks, I may get the grub first then.

 

[tomb]

Quote:

Thanks, I may get the grub first then.

Highly advised.  If you read through just the most recent posts, you'll see the trouble that's had with even experienced builders.  We will improve that quite a bit for the production version, no doubt, with cobaltmute's design skills.  However, as cobaltmute infers, it's doubtful that it will ever attain a beginners' or "first kit" status.  I can tell you right now that the price of a kit will be more than you are willing to invest in just as an experiment.
 
All that said, it's worth every bit of the trouble and complexity involved in building it, but you need prior experience - period.

 

[Mullet]

As the guy who almost killed his project, I agree with what the fellas are saying. This project is not for beginners. I have to be honest this is the first time after doing a few Gamma-2/1s and a GrubDAC that I've actually not had a DAC not work after firing it up for the first time. Perhaps, my mistakes could have been avoided if I changed out U9 sooner and didn't fuss with the PCM2707. I hope what I've been through can help others with regard to how hot to keep your iron, not to soak a board into water after cleaning it with alcohol, how to not lift pads, etc. I learned that using a solder sucker on these pads for cleaning excess chip quik solder is not the answer and using solder wick is the answer. I still have to obtain an LMH6643 to really complete the PCB and make sure there are no oscillations. The next step for me is to work on properly measured panels. I'm just waiting on more solid board measurements so I don't end up having to order panels twice.
 
This is where I got the erroneous info for using soap and water after you use isopropyl alcohol... I knew I wasn't crazy
http://www.diyaudio.com/wiki/The_Wire_Headphone_Amp_Build_Wiki

 

[Avro_Arrow]

I'm still on hold for a toaster oven...
 
I may have to break down and hand solder it.

 

[cobaltmute]

I'm still on hold for a toaster oven...

I may have to break down and hand solder it.

Skillet method on the stove works as well for doing the "hard" side of the board.