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02-05-2017 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,103
Joined on 10-12-2006

Post #: 21
Post ID: 22950
Reply to: 22948
Neutrality
Yes, try ethanol (with as little water in it as possible). Contact cleaner is typicalyl just that.  I have ass-u-me(d) that part of your post-solder cleaning involves something alkaline, as well, to neutralize the solder flux. That's why I also water wipe (then dry) to finish, to get the alkaline residue off.  I tend get more build-up on the joints than others because I flux the hell out of thick parts, especially, and this absolutely requires scaling as part of cleaning the joint.


Paul S
02-05-2017 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,103
Joined on 10-12-2006

Post #: 22
Post ID: 22951
Reply to: 22950
One Example (of MANY!)
Here's one example of what I mean regarding cleaning a solder joint:

https://gokimco.com/chemtronics-es835b-flux-off-rosin-flux-remover.html?gdffi=a2b2595eeb2e44a8bc2e332d298712bc&gdfms=D2663A01824B473FAC1E75660BF93E39&gclid=CLWNztik-tECFUlNfgodZUgKGg

Plenty of options, all "base" in nature.


Best regards,
Paul S
02-06-2017 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 441
Joined on 01-07-2006

Post #: 23
Post ID: 22952
Reply to: 22951
Flux remover
Paul, I'm using this one: http://uk.farnell.com/kontakt-chemie/kontakt-pcc/flux-remover-aerosel-200ml/dp/2532504



Cheers,
Jarek
02-06-2017 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,103
Joined on 10-12-2006

Post #: 24
Post ID: 22955
Reply to: 22952
Only Because of the Bubbles...
No doubt there are any number of ways to get a nice coating of natural shellac over clean, chemically neutral, soldered connections, but you did mention you have "bubbles", and there must be "chemical" reasons for this.  I looked up the cleaner you are using, and there is no indication that it is alkaline, which a specialized flux remover should be, as far as I know. One first needs to remove the residual rosin (including scraping, as necessary), then one needs to neutralize the residual acids (from the flux).  Then one can clean it in a way that leaves it "neutral". Then the traditional shellac (with denatured alcohol) can be applied in thin layers.

Here's a spec sheet I found on your cleaner.  You can check your cleaner with litmus strips, of course.  However you manage it, you are aiming at a clean and chemically "neutral" joint under the shellac, and no "bubbles".

http://docs-asia.electrocomponents.com/webdocs/136b/0900766b8136b1bf.pdf

Best regards,
Paul S
02-06-2017 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 441
Joined on 01-07-2006

Post #: 25
Post ID: 22956
Reply to: 22955
PCC data
Paul, thank you for your explanations. No idea if PCC is alkaline but according to its manufacturer it has some isoalkanes and isopropyl. Visually it does remove it quickly (also my Cardas solder is not leaving much of a flux): http://www.kontaktchemie.com/KOC/KOCproductdetail.csp?product=KONTAKT%20PCC

I'll ass-u-me that the bubbles are due to the slowly evaporating isopropyl in too thick applications of the coating and I'll leave the phonocorrector with the bubbles. I have no intention to go cleaning all the joints. Will try the denaturated alco solution with next solderings.
Thanks again,
Jarek



Cheers,
Jarek
02-06-2017 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,103
Joined on 10-12-2006

Post #: 26
Post ID: 22957
Reply to: 22956
Flux Is Acid
You need acid (flux) to flash clean the metals as they are being soldered and prevent a "cold joint"/poor bond that not only spoils transmission initially but it oxidizes and worsens faster over time. If you've used enough flux for a good joint (especially with thicker/heavier gauge materials), then you will have acid and also acidic oxides on the metals after soldering. No matter visually "clean", the metals need to be chemically neutralized to stop oxidation and/or electrolysis happening under the shellac, which only works, after all, to keep oxygen from a "perfect" soldered joint. No sense putting shellac over a corrupted joint

Paul S
02-06-2017 Post does not mapped to Knowledge Tree
rowuk


Germany
Posts 222
Joined on 07-05-2012

Post #: 27
Post ID: 22958
Reply to: 22957
Vintage connections better
Remember wirewrap with the sharp cornered posts? The amplifiers that I built that way are still noise free after 40 years. 20 turns or so per post work just fine and those connections can be shellacked.


Whenever I feel blue, I start breathing again.
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