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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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16th Jan 2020, 6:59 pm | #1 |
Triode
Join Date: Sep 2016
Location: Banbury, Oxon, UK.
Posts: 33
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Brown substance on Solder Joints
I’m working on an Advance signal generator, and all of the solder joints in it are covered in a brown substance. I’m wondering if someone could tell me what it is, and how problematic it will be if it goes under the soldering iron. Tips on how to remove it pre-soldering would also be appreciated.
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16th Jan 2020, 7:17 pm | #2 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
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Re: Brown substance on Solder Joints
I'll be interested too. Encountered this before and just ploughed on through, cant recall it giving me any major problems
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16th Jan 2020, 7:39 pm | #3 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Brown substance on Solder Joints
It doesn't look like flux-residue. In times-past on 'professional/military' gear it was quite normal for soldered joints to be inspected after soldering [by someone other than the solderer, obviously] and a lacquer or paint was applied to each joint to confirm it had been inspected. I've not come across brown lacquer being used for this, but a small red paint-dot on each joint was quite commonplace in WWII-and-subsequent military equipment.
As to what to do about it - I wouldn't worry - just solder through it. |
16th Jan 2020, 7:53 pm | #4 |
Dekatron
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,809
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Re: Brown substance on Solder Joints
Yep, inspectors at Thorn where I worked had to mark every soldered joint with a felt tip marker pen to show that it had been inspected. This was also done on PCBs. It's just marker pen ink, not a problem to resolder, remover solder, whatever.
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16th Jan 2020, 7:53 pm | #5 |
Heptode
Join Date: Dec 2003
Location: South Yorkshire, UK.
Posts: 900
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Re: Brown substance on Solder Joints
I was going to say QC marks. Those Advance signal generators are very good.
Chris
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16th Jan 2020, 8:13 pm | #6 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Brown substance on Solder Joints
Is it possibly shellac?
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17th Jan 2020, 12:16 am | #7 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
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Re: Brown substance on Solder Joints
I have seen this in red and also brown, and think that it is some sort of varnish or shellac. It certainly seems to preserve the solder in a shiny state (and does not seem to cause a problem when re-soldering) If attacked with a screwdriver or similar i should think it will crack off in flakes.
Dave |
17th Jan 2020, 1:26 am | #8 |
Triode
Join Date: Sep 2016
Location: Banbury, Oxon, UK.
Posts: 33
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Re: Brown substance on Solder Joints
It certainly seems to give off a lot of smoke. I got a good whiff of it by accident the other day (I have an exhaust fan, but stood over the joint for a better angle) so knowing what it is would be nice. I had heard about the QC marking before, but this seems to be an actual deliberate coat, rather than a small dab.
I think I’ll try washing the joint with IPA and see if it does anything. If it’s shellac it should dissolve with alcohol. |
17th Jan 2020, 9:16 am | #9 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Brown substance on Solder Joints
If it is shellac, meths is the solvent (or ethyl alcohol). Not sure if IPA will work.
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17th Jan 2020, 10:29 am | #10 |
Heptode
Join Date: Jun 2017
Location: Southport, Merseyside, UK.
Posts: 646
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Re: Brown substance on Solder Joints
My father's two emi group radios were what was called back in 1937 "tropicalised"
This appeared as a brown coating which in hindsight i am sure was shellac. It was certainly on the transformers and chokes and their solder terminals but cannot remember if it was on the other components. I have recently dismantled a Grampian PA amp for spares. It is early 1950' I think and the transformers and joints had a similar brown coating. There was no problem in de-soldering.
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17th Jan 2020, 10:33 am | #11 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
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Re: Brown substance on Solder Joints
Very interesting this, I've often thought that it was aged solder flux, you never stop learning.
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17th Jan 2020, 11:06 am | #12 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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Re: Brown substance on Solder Joints
Yes, shellac was commonly applied - not just to soldered joints but often found on nuts & bolts.
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17th Jan 2020, 11:46 am | #13 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,552
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Re: Brown substance on Solder Joints
When I was at Leevers Rich in 1969 the inspector always put a dab of red varnish on each joint to show it had been inspected - I began to doubt the efficacy of this procedure when I found a joint which had not been soldered at all but nevertheless had its dab of red varnish.....
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17th Jan 2020, 2:29 pm | #14 | |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,529
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Re: Brown substance on Solder Joints
Quote:
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17th Jan 2020, 4:42 pm | #15 |
Dekatron
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,809
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Re: Brown substance on Solder Joints
Workers will always find ways 'navigate' around procedures that take time.
At Thorn we also did work for the military. For such contracts and equipments, mechanical wire strippers were not allowed because of the risk of weakening the copper conductors and the chance of them severing as a result of vibration, shock etc in battle. So, hot wire strippers were designated for use of. I won't comment on whether or not I ever saw mechanical strippers being used.
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