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abelincoln



Joined: 02 Nov 2007
Posts: 60
Location: Raleigh, NC

PostPosted: Fri Nov 02, 2007 1:59 pm    Post subject: advice for a newbie Reply with quote

I've been reading this forum for a while now and checking into the ezDAC and ezDual projects. Thanks to all of the posters for sharing your knowledge.

Everybody here seems like such an expert and I don't want to dilute this forum with stupid questions. But could I ask for some advice from some of the people who have successfully put an ezDAC together? Maybe this would be helpful for other newbies who would otherwise be put off by the level of difficulty of this project.

So in general, before I start my project is there anything about it that I should know that maybe some of you wished you had known beforehand?

In specific, I'm a little worried about soldering surface mount chips to the PCB. A friend of mine says he can get some guys at his work to do this for me. He says they use a technique called 'wave soldering.' Has anybody heard of this or know if it's appropriate for the ezDAC?

Thanks in advance.
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RichA



Joined: 11 Jun 2007
Posts: 115
Location: Stafford, UK

PostPosted: Fri Nov 02, 2007 10:39 pm    Post subject: Reply with quote

Welcome Smile. No such thing as a stupid question.

I think the failed builds were generally due to the exposed ground plane on the first revision of the board - the new batch has a soldermask, and a silkscreen, so builds should be a lot easier.

Soldering the ICs is easier than you'd first think. There are several methods of doing it - I prefer using a fine-tipped(0.5mm) soldering iron, and fine-cored solder, with good flux, and just touching each leg. But one can 'flood and suck' by loading the IC legs with solder, heating the blob with the iron, and sucking it away. Another is to use solder paste and an electric hotplate.

I think the various options have been quite well discussed on here in the past. Smile

--Rich
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ezkcdude
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Joined: 11 Jun 2007
Posts: 302
Location: Atlanta, GA

PostPosted: Fri Nov 02, 2007 11:45 pm    Post subject: Re: advice for a newbie Reply with quote

abelincoln wrote:
Everybody here seems like such an expert and I don't want to dilute this forum with stupid questions. But could I ask for some advice from some of the people who have successfully put an ezDAC together? Maybe this would be helpful for other newbies who would otherwise be put off by the level of difficulty of this project.


Welcome! There's never a question that's stupid. Of course, they also say there's a first for everything - but I kid Laughing. Anyway, some people here have more expertise than others, but I think everyone is very helpful. I only started in DIY a little over a year and a half ago, so it really isn't as hard as you might think. As for the boards, I hope Rich is right, and that it will be easier with the soldermask/silkscreen.
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abelincoln



Joined: 02 Nov 2007
Posts: 60
Location: Raleigh, NC

PostPosted: Sun Nov 04, 2007 6:23 pm    Post subject: Reply with quote

Thanks for the encouragement. Between that, soldering tools at work, and a friend who can bail me out if necessary, I think I better just get started with it. Rich, I did look at the forum about soldering methods. It seemed like everybody just uses their preferred method and there really is no consensus on which is best. My plan is to try soldering the individual chip legs and if that doesn't work, resort to the 'flood and suck' method you described.

I have one quick question (hopefully not uniquely stupid Confused ). Is it best to use 'silver' solder -- 62%-tin, 36%-lead, 2%-silver? Wikipedia and RadioShack.com both recommend it for SMT and I was wondering if I could just use it for all of the parts. Would 0.015" diameter, rosin core silver solder do the trick?

Thanks again.
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ezkcdude
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Joined: 11 Jun 2007
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PostPosted: Sun Nov 04, 2007 7:35 pm    Post subject: Reply with quote

abelincoln wrote:

I have one quick question (hopefully not uniquely stupid Confused ). Is it best to use 'silver' solder -- 62%-tin, 36%-lead, 2%-silver? Wikipedia and RadioShack.com both recommend it for SMT and I was wondering if I could just use it for all of the parts. Would 0.015" diameter, rosin core silver solder do the trick?


Wikipedia and RadioShack...not the best places to go for electronics advice. What I use, and probably most people here, is something like Kester 63/37 solder. It's a eutectic solder which basically means it flows better. The one you mentioned is probably also eutectic, but I wouldn't pay much more for it, simply because of the silver content. What you want to stay away from is 60/40 blends or the lead-free solders. They are harder to work with. I use this stuff for pretty much everything:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=KE1405-ND

It's digikey part #KE1405-ND, 28AWG (0.015") 63/37 No-Clean solder (aka Kester 245). The "No-clean" means exactly that. You don't have to worry about leaving residue on the board. You can buy 1 lb for about $50, or 1/2 for about half that. It will last you a long, long time.
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RichA



Joined: 11 Jun 2007
Posts: 115
Location: Stafford, UK

PostPosted: Tue Nov 06, 2007 12:32 am    Post subject: Reply with quote

abelincoln wrote:
Thanks for the encouragement. Between that, soldering tools at work, and a friend who can bail me out if necessary, I think I better just get started with it. Rich, I did look at the forum about soldering methods. It seemed like everybody just uses their preferred method and there really is no consensus on which is best. My plan is to try soldering the individual chip legs and if that doesn't work, resort to the 'flood and suck' method you described.


If you have spare ICs, then you could do what I did - grab some cheap SSOP-DIP adapter boards. They're often on eBay, or Futurelec do them quite cheaply. Good way to get some practise in without ruining anything Smile.

There is no general consensus, because like underwear, it's a matter of personal taste. The most important part, IMO, is ensuring that the IC is completely lined up correctly, then tack down opposing corners. I then coat both IC sides with flux, then touch each IC leg and pad for a half second or so, then touch .5mm solder on the end of the leg. Do this for all legs, then add extra flux, and touch each leg again. Be sure to clean it off afterwards - IPA and a stiff brush(toothbrush?) works well.

I believe I'm using this solder, but it has been a while since I ordered it, so it may not be exactly the same. But I found it nice and easy to use - remember to use a little flux as well, as it'll make the job much easier.

--Rich
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abelincoln



Joined: 02 Nov 2007
Posts: 60
Location: Raleigh, NC

PostPosted: Wed Nov 07, 2007 1:18 pm    Post subject: Reply with quote

Evan and Rich, thanks once again.

Evan, I'm going to use something like the Kester 245 solder you suggested. I tried to call about the half pound of it today but they don't stock it any more and my order has already shipped. I think I can find something locally (avoiding Radioshack, of course).

Rich, sounds like using a lot of flux is a good idea, even though the stuff you use is rosin core? When you say 'tack opposing corners' you mean to tin the pads and solder the chip down by two of the corner legs that are diagonal from each other? Then once the chip is aligned properly you hit each remaining leg/pad with flux, iron, then solder? I'll have to check into the SSOP-DIP adapter boards.

With any luck my parts and boards will arrive before the weekend. I'm pretty excited.
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ezkcdude
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Joined: 11 Jun 2007
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Location: Atlanta, GA

PostPosted: Wed Nov 07, 2007 4:19 pm    Post subject: Reply with quote

Another tip is to use a "flux pen". It looks like a magic marker, but "writes" flux. I really like them, and they are relatively cheap - under $10. Good luck!
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RichA



Joined: 11 Jun 2007
Posts: 115
Location: Stafford, UK

PostPosted: Wed Nov 07, 2007 8:28 pm    Post subject: Reply with quote

Yes, diagonally-opposing corners, to keep the IC in perfect alignment with the pads. Smile

Flux is excellent - regardless of solder used, it should help eliminate and solder-joints between IC legs, and will keep the leg and pad clean whilst solder flows, which results in a better joint. Hopefully... ;)

--Rich
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abelincoln



Joined: 02 Nov 2007
Posts: 60
Location: Raleigh, NC

PostPosted: Tue Nov 13, 2007 3:53 pm    Post subject: Reply with quote

I've got kester solder and a flux pen on order; my boards and parts have already arrived. I had braced myself for the size of the dac and clock chips but the surface mount capacitors and resistors are really tiny. Good thing I've got a good pair of tweezers and I'm looking into picking up a magnifying lamp from Office Depot maybe.

I now have a question about the orientation of the parts. Most of the parts I can see in the pictures which way to align them but how about the capacitors? For the resistors I'm assuming that it doesn't matter which way they go?

I think at this point I really need to read an introduction to electronics textbook but it's hard to make myself do this when my dac is sitting right in front of me just waiting to be assembled.
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ezkcdude
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PostPosted: Tue Nov 13, 2007 4:02 pm    Post subject: Reply with quote

abelincoln wrote:


I now have a question about the orientation of the parts. Most of the parts I can see in the pictures which way to align them but how about the capacitors? For the resistors I'm assuming that it doesn't matter which way they go?



All the smd (passive) components -resistors, ferrites, and caps - are bidirectional - doesn't matter which way you orient them. I think the soldermask really helps with the building. I just started soldering last night, and I think it is easier than before. The 0805 can be moved around pretty easily, if you mess up. (You'll notice that right away.)
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abelincoln



Joined: 02 Nov 2007
Posts: 60
Location: Raleigh, NC

PostPosted: Thu Nov 15, 2007 3:39 pm    Post subject: Reply with quote

OK, so the smd parts aren't polarized meaning that it doesn't matter which way they go. And I just found your rule of thumb for the rest of the parts:

The pads indicate positive/negative (square=positive), and the lytic caps usually have 2 indicators for polarity: 1) typically a big fat "+" or "-" sign and 2) the positive lead is much longer.

So I think I'm good to go here. Two really quick questions:

Jumpering V1-V2-V3 just means that I need to solder two wires that will connect the small square pads (I'm assuming the large pads are for using separate power supplies) between V1-V2 and V2-V3?

What are CRDL and CRDR?

Thanks as always.
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ezkcdude
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PostPosted: Thu Nov 15, 2007 4:26 pm    Post subject: Reply with quote

abelincoln wrote:

Jumpering V1-V2-V3 just means that I need to solder two wires that will connect the small square pads (I'm assuming the large pads are for using separate power supplies) between V1-V2 and V2-V3?


Here's a diagram. You can do any of the following.



abelincoln wrote:

What are CRDL and CRDR?


They are current regulating diodes, which are supposed to bias the op amps into class A. They are completely optional and not recommended unless you really know what you are doing. Leo said they work, but to my knowledge, nobody has tested them yet with the new version. If you want to read more, here is one place to start:

http://tangentsoft.net/audio/opamp-bias.html

I'm glad you're asking these questions before you start. It will save you some headache later. Good luck.
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lauret



Joined: 06 Nov 2007
Posts: 9

PostPosted: Sat Nov 17, 2007 12:00 pm    Post subject: Reply with quote

I got a little bit interested in those diodes.

But I can't find a 1N5314 at either Farnell (only US supply) or Digikey. Is there also a replacement available?
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ezkcdude
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Joined: 11 Jun 2007
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PostPosted: Sat Nov 17, 2007 1:53 pm    Post subject: Reply with quote

I'm not sure. They are fairly hard to find. However, some people have a bunch already. I could buy some from Mouser and ship them to you, if you're interested. However, I'll be gone all next week.
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