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Mod-286 build thread
Mod-286 build thread
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Old 10th July 2017, 05:24 PM   #1
HarmonicTHD is offline HarmonicTHD  Switzerland
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Default Mod-286 build thread

Dear Neurochrome Modulus-286 builders

After there is already a thread for the Mod-86 I thought for the sake of clarity I open a separate one for the Mod-286. Tom and / or the moderators please let me know whether you rather want that content somewhere else.

Other than that I am about to start my second ever Audio DIY project. I intend to build two Modulus-286 as Monoblocks to drive my KEFsR700 while being fed directly from the balanced output of my Auralic Altair.

The boards from Tom arrived in mint condition and I already got the parts from Mouser and therefore I am about to get started.

As I am new to SMD soldering, I got one of these practice kits on ebay, which Bill in another thread recommended and I watched some YouTube videos.

However I have my first choice to make. Which solder to use? Currently I have two solders at home. One with Pb another with Ag? I'd go with the Ag one or is the melting temp too high for some of the ICs?

Thx
SH
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Old 10th July 2017, 06:18 PM   #2
BrianL is offline BrianL  United States
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Mod-286 build thread
Practice kits are a good idea. Either solder should work just fine. It does take a higher temperature to do the Pb-free solder, but as long as your soldering iron has a way to adjust the temperature, you should be fine. The bigger heat risk is from bad technique -- heating for too long or repeated applications of heat. My own preference is for eutectic lead-bearing solder, like your Sn60Pb38Cu2 as it has worked well for me with less issues/hassles than the various Pb-free solders.

Tom has some good soldering info on his site.
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Old 10th July 2017, 10:07 PM   #3
tomchr is offline tomchr  Canada
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Thank you for starting a build thread. I'm looking forward to seeing your build develop.

As Brian mentions above, I have a small dissertation on how to choose solder on my website. You can find it here: https://www.neurochrome.com/choosing-solder/

Tom
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MOD686: Up to 240W/8Ω, <0.00025% THD. MOD86: 40W/8Ω, 0.000054% THD. HP-1: 3W/20Ω, -130dBc THD, 128dB DNR.
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Old 11th July 2017, 05:33 PM   #4
HarmonicTHD is offline HarmonicTHD  Switzerland
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Hi

Thanks for the soldering hints and also for pointing out Tom's article on that. Although I had read it before I had lost track as it is quite challenging as a noob to remember all the important things. So please bear with me.

So for today's progress. I started once more with my practice board to get the solder temps right and ended up with ca. 370-380degC. I have a digital temp controlled solder station but don't know how accurate the display really is. So don't take it for granted. As described within Tom's excellent description I started with the resistors. However I had to crank up the temp (430degC) considerably for the big resistor SMDs. I assume they and the pads draw more heat. At the end of the hour I had soldered the first three resistor values on both boards, checked them off in the BOM and on the package as they tested out ok.

Phew. Now off to dinner.

Please comment or had hints on my solder result. Not all is lost yet ;-)
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Old 11th July 2017, 06:06 PM   #5
tomchr is offline tomchr  Canada
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370 C (700 F) is about right for leaded solder. If you can't get the solder to flow well on the larger components at that temperature, try a larger tip before cranking up the temperature.

Looks like you need a bit more practice with the 0603 size if you plan to solder a lot of those. Thankfully, the MOD286 is 0805 or larger, with the exception of a small handful of diodes that are annoyingly small (SOD-123 package). I'd say do another row of 0805 and see if you can use slightly less solder and make it drape a bit better on the resistor terminals. You might need to hold the soldering iron on the resistor terminal for a second longer to make the solder drape nicely.

You're doing well so far, though. Good call on getting one of those SMD practice boards. They're only a buck or two on eBay.

Tom
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MOD686: Up to 240W/8Ω, <0.00025% THD. MOD86: 40W/8Ω, 0.000054% THD. HP-1: 3W/20Ω, -130dBc THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 11th July 2017, 06:20 PM   #6
HarmonicTHD is offline HarmonicTHD  Switzerland
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Thanks Tom. Will do. Just to clarify. I forgot to mention that I used the non lead solder with Ag. Therefore I would expect higher temps, wouldn't I?
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Old 11th July 2017, 07:40 PM   #7
BrianL is offline BrianL  United States
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Yes, Pb-free solder melts at a higher temperature than SnPb types. I've seen recommendations in the 750-800F range (400 - 425C). It varies depending on the alloy, so check the solder manufacturer's datasheet. As Tom said, for physically larger components you should use a bigger tip to allow more heat flow to the part. Just cranking up the temperature of a tiny tip is not the way to get there.
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Old 11th July 2017, 07:40 PM   #8
tomchr is offline tomchr  Canada
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I had to consult my own website to get the melting points of the lead-free solder with Ag. It melts at around 225 C - about 50 C higher than leaded solder. I'd crank the soldering iron up to 425 C. Or consider switching to 60/40 or 63/37 leaded solder. They're a lot easier to work with. It also looks like you have some Sn/Pb/Cu available. I'm not familiar with that alloy, but you could try it out.

Edit: A quick Wikipedia read reveals that the 60/38/2 Sn/Pb/Cu alloy increases the hardness of the solder joint and prevents the molten solder from dissolving the metals in the joint. It should behave like 60/40 in actual use. It enters the plastic region at 183 C and melts at 190 C. I'd use a 370 C iron with that.

Tom
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MOD686: Up to 240W/8Ω, <0.00025% THD. MOD86: 40W/8Ω, 0.000054% THD. HP-1: 3W/20Ω, -130dBc THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right

Last edited by tomchr; 11th July 2017 at 07:47 PM.
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Old 11th July 2017, 08:08 PM   #9
HarmonicTHD is offline HarmonicTHD  Switzerland
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Wow. You guys are great. Thank you so much. The Sn/Pb solder I had already for years and I am used to it and it's easy to work with. I guess I run a few more practice rounds on the tryout board and see if I can get more proficient with the Ag solder.

BTW. I am using currently a 0.6mm chisel shaped soldering tip. Should I get a bigger one for the larger parts?

Do you think I have to redo the already soldered parts? Is there a way to salvage or improve the joints? Or would I only make things worse by subjecting these parts to heat again?

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Old 11th July 2017, 08:12 PM   #10
tomchr is offline tomchr  Canada
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I wouldn't bother with redoing anything on the practice board. If you've started soldering the Modulus-286, I'd take a close look at the solder joints. If they look good - i.e. are shiny in appearance and drapes nicely on the component terminals - I wouldn't bother redoing anything. However if the solder balls up on the component terminals, I'd wick up the solder using de-solder braid (Solder Wick is one brand name) and redo the joints. You'll probably find that there's enough solder to hold down the component once you've wicked up "all" the solder. That's fine. Wick up as much as you can and re-solder.
It's probably overdoing things to rework the solder joints, but then again you're spending a good chunk of time and money. It's more fun to have the project work from the start so it seems wise to spend a little time up front.

Tom
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Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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