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In Reply to: RE: DIY phono stage, wire gauge question posted by John Elison on February 11, 2017 at 20:52:47
Nice job with the wire! No gaps in the twists.
BTW just a comment regarding the tip temperature. I don't doubt your judgement on timing for heat application vs solder flow, but the other less experienced hobbyists here are in great danger of dry joints if they ignore the rating of the solder and choose a high temperature tip to speed up things up as this will result in the flux boiling off. The eutectic point depends on the solder Pb/Sn blend, but Rosin Flux is optimum at 280°C and beyond 315°C (600°F) starts to become less effective. This is the temperature the part legs, pad and solder need to be at for the highest quality weld, so choosing a 700°F tip requires judicious care in not allowing the solder to remain in contact with the hot tip beyond the time required to melt the solder and allow it to flow otherwise there is a greater risk of reduced flux effectiveness which impacts on joint reliability. I doubt anyone here is soldering with unleaded solder, but that is far more difficult to work with and requires a considerably greater time for heat application - the temptation is simply to wind up the temperature to speed things up. However, this is counterproductive and makes for a nasty mess and poor joint reliability.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Follow Ups:
i'm using a lead-free solder. 96% Tin, 3% Silver, .5% Copper. I didn't have an issue until my last few resistors(larger ones) and the solder just turned into a ball and didn't flow. It did take 3-5 seconds of contact for it to work.
John beat me to it with his recommendation! It's all about heat transfer. Smaller tips are great for tight spaces, but generally the limited heating contact area makes for a more difficult and challenging wetting of the surfaces.
My main suggestion when working with high silver content solder is to ensure plenty of ventilation or use a fume extractor as the fumes are worse for you than the leaded solder. Wear gloves to avoid touching and transferring oils and moisture to the parts to be welded. Also avoid the temptation to touch the welds with your fingers afterwards when admiring your handiwork! I was very guilty of that until I realised how quickly dendrites form when the circuit is energised. Electromigration of the silver ions is a real problem with unleaded solder and the dendrites can form within minutes depending on the applied voltage and the relationship between track potential. The dendrites will even go around the edges to the other side of the board!! Track bridging can occur within hours in the presence of moisture even if the weld was perfect initially.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
You should use a larger tip for larger parts. I bought a variety of different size tips with my Weller soldering iron. I use 700-degrees F for all my soldering jobs. I just use a larger tip for larger parts. I think the most important thing in building DIY components is learning how to solder properly.
Good luck,
John Elison
I certainly don't doubt your superior knowledge of solder and flux, but I've been soldering for years. I was an electronics technician before becoming a mechanical engineer and I have never been able to solder successfully with a 600-degree tip. I've always found 700-degree tips to be optimal for my soldering technique. Also, I don't apply solder with the soldering iron. I use the soldering iron to heat the joint and I apply solder directly to the joint. Furthermore, I never leave solder on the tip. I clean it with a wet sponge before every solder joint. That's why modern soldering irons come with a tip-cleaning sponge.
My technique is to clean the soldering iron with a wet sponge and then apply a small amount of solder to the tip to allow better heat transfer to the joint. Then I touch the solder directly to the joint and remove the soldering iron and solder immediately when the solder flows into the joint. This technique works well for me.
Best regards,
John Elison
Your technique is absolutely beyond reproach and is the same as I was taught - "heat the part not the solder" as well as not reworking joints solely for the purpose of improving aesthetics. I absolutely wasn't suggesting you didn't have the right technique, I was only trying to highlight some cautionary points for the less inexperienced hobbyists who will be following your phono stage project with interest (as have I). The preferred temperature obviously depends on the solder composition and choice of flux - FWIW I also use 700F for my 60/40 leaded solder (for home jobs I still use leaded solder). However, high silver content solder is often promoted for use with audio and this requires a bit more care in adjusting the time of contact before applying solder. Anyone unused to the challenges of high silver content solder will generally wind up the temperature to achieve the same heating time for solder flow that they are used to. The main issue is around the long term reliability of joints and the higher temperatures used in this manner will be a greater risk for weld integrity.
Your project has certainly piqued my interest to experimenting with a tube stage! Thanks for sharing it :)
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Hi Anthony,
I thoroughly enjoyed assembling the two VTA kits. It had been years since I assembled such elaborate components. You should try it. I don't think you'll find a less expensive way to obtain high-end tube components.
If you find any other kit manufacturers, let me know. I still might build a pair of tube monoblock power amplifiers.
Best regards,
John Elison
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