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stuck component feet and weired solder
Old 16th February 2017
  #1
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stuck component feet and weired solder

hey guys,
im working on some terrible pcbs. they are pretty old and seem a little corroded.
there is one big 0V trace that gives me headaches. i cant get the old capacitor legs out of the holes no matter what i try. i have been re-capping for years. i use a high end weller desoldering iron but i have no luck. all other pin holes reacted as usual - no problem. its just that big trace.
it seems as if the old solder wont even react to heat. it doesnt move - or get fluid. its just stuck. i have never seen solder of this behaviour.

any idea what might cause this and what i can do about it. i applied crazy amounts of heat with no luck. i got most of the legs out but some are stuck. where i was able to remove them i still cant get out the solder remains. on those holes i will most likely drill out the old solder with a fine pcb drill. but i need to somehow remove the remaining cap feet. can additional flux help maybe?
Old 16th February 2017
  #2
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...even fluxshows no effect. when applying extr solder to the stuck cap feets it crumbles up as well and reacts akwardly.... maybe that big 0v trace acts as a huge heatsink? im lost...
even solder wick does not react with it

Last edited by salomonander; 16th February 2017 at 05:04 PM..
Old 16th February 2017
  #3
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Just flood it with some new 60/40 multicore, that should get the old stuff moving

The first step in desoldering is (counter-intuitively) always to add more solder.
Old 16th February 2017
  #4
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thanks guys. this is the weirdest pcbi ever touched. i was to remove all legs now with some new solder that i dipped heavily in flux. i was too shy at first. no way getting the remaining solder out - i will drill that away.
Old 17th February 2017
  #5
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ok this pcb is cursed. i did get it all clean. but now no new solder stickts to the pads. at first i thaught they are corrodet - but i have cleaned them perfectly. first with some flux, then isoprop and a fiberglassbrush attached to a drill. i see 0% corrosion but my solder wont make a proper contact.

could this have to do with the big 0v trace stealing my heat? or is there some chemical reaction that might cause this?
it "feels" as if my solder iron doesnt have any heat - the new solder crumbles - i have never seen this. if the heatsink theory makes sense i might have to work with a way bigger solder tip to apply more heat... any idea is welcome
Old 17th February 2017
  #6
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Quote:
Originally Posted by salomonander View Post
t seems as if the old solder wont even react to heat. it doesnt move - or get fluid. its just stuck. i have never seen solder of this behaviour.
What Lumbergh said.

It sounds weird. But the way to melt old, cranky solder is with new solder. Really. It'll even work with a tiny, coolish iron. Flow a little new solder onto the joint, and the old solder will melt. I know nothing about metallurgy or why it works, but it works.
Old 17th February 2017
  #7
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Quote:
Originally Posted by Brent Hahn View Post
What Lumbergh said.

It sounds weird. But the way to melt old, cranky solder is with new solder. Really. It'll even work with a tiny, coolish iron. Flow a little new solder onto the joint, and the old solder will melt. I know nothing about metallurgy or why it works, but it works.
thanks mate,
problem is it doesnt. it just clumps to the other clumb so to say. dont know what this is. i recapped for years and never came across ajything like this....
solder makes no real contact to the pads - which apparently are cursed
Old 17th February 2017
  #8
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Quote:
Originally Posted by salomonander View Post
could this have to do with the big 0v trace stealing my heat? or is there some chemical reaction that might cause this?
Yes, of course a big copper trace will dissipate the heat from your soldering iron - this is why well-designed boards have "thermals", or cutouts around pads in big traces or grounds to allow the pad and PTH to heat properly. In these cases . . . attempting to overcome the thermal mass by heating it longer isn't very effective, as the copper trace simply pulls down the temperature of the iron, and even most feedback-controlled soldering stations are limited in how efficiently they can transfer heat from the element to the tip (Metcal being somewhat of an exception).

A big stained-glass style tool like those Audiospacific suggests may seem a bit ham-handed, but they're necessary in some cases. You basically need something where the tip of the iron has enough thermal mass in and of itself, to be able to compete with the mass of the trace.
Old 17th February 2017
  #9
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Quote:
Originally Posted by kirkus View Post
Yes, of course a big copper trace will dissipate the heat from your soldering iron - this is why well-designed boards have "thermals", or cutouts around pads in big traces or grounds to allow the pad and PTH to heat properly. In these cases . . . attempting to overcome the thermal mass by heating it longer isn't very effective, as the copper trace simply pulls down the temperature of the iron, and even most feedback-controlled soldering stations are limited in how efficiently they can transfer heat from the element to the tip (Metcal being somewhat of an exception).

A big stained-glass style tool like those Audiospacific suggests may seem a bit ham-handed, but they're necessary in some cases. You basically need something where the tip of the iron has enough thermal mass in and of itself, to be able to compete with the mass of the trace.
makes perfect sense. ill get one of the big shovel like tips from weller tomorrow and try again. thanks for all the help!
Old 17th February 2017
  #10
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ps: this is the pcb - a gml. its the big trace that four axials leed to.
Attached Thumbnails
stuck component feet and weired solder-gml.jpg  
Old 17th February 2017
  #11
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You really need to just cut the leads on those caps.

The reason you can't solder it is because of the stop lack that is sprayed over the top of the trace. The way to solder it is to scratch the stop lack off until you get down to the bare copper.
Old 17th February 2017
  #12
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Quote:
Originally Posted by salomonander View Post
it just clumps to the other clumb so to say. dont know what this is. i recapped for years and never came across ajything like this....
solder makes no real contact to the pads - which apparently are cursed
Yeah sounds like not enough heat too, I have a weller W61 mains iron with big hot tips for jobs like these, speaker terminations or working near heatsinks. Thats another reason for suggesting the 60/40 multicore - to dilute the existing (presumably lead free) solder and bring the MP down to a more workable temp and to take advantage of the aggressive ersin flux.

And yes you need to remove any stop lacquer or conformal coatings before starting.
Old 18th February 2017
  #13
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Quote:
Originally Posted by Vitalis View Post
You really need to just cut the leads on those caps.

The reason you can't solder it is because of the stop lack that is sprayed over the top of the trace. The way to solder it is to scratch the stop lack off until you get down to the bare copper.
nah...its a heat thing. nothing else makes sense. i cleaned the contacts with a fiberglass brush on a drill. scratched off a fair bit. they are as shiny as possible. its a misdesign by the hands of mr massenburg and nothing else he might was great about designing circuits but he knew little about pcb design. looking at all the other solder joints that were originally made by gml - they all look bad on this trace. they had the same issue. the poster above you mentioned the cause. its misdesign.....
Old 18th February 2017
  #14
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Whoaa there ... GM does not **** about when it comes to circuit design, build or test.
Old 18th February 2017
  #15
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Quote:
Originally Posted by Lumbergh View Post
Whoaa there ... GM does not **** about when it comes to circuit design, build or test.
i know.... bohaaa. but that pcb is f*cked.. its just the pcb...not the circuit. its sounds amazing though if you want clean love that preamp
Old 18th February 2017
  #16
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Quote:
Originally Posted by salomonander View Post
its a misdesign by the hands of mr massenburg and nothing else he might was great about designing circuits but he knew little about pcb design. looking at all the other solder joints that were originally made by gml - they all look bad on this trace. they had the same issue. the poster above you mentioned the cause. its misdesign.....
I disagree, and I bet you if I had the PCB here that I could unsolder it. Mr GM does indeed know what he's doing. It's not his job to manufacture the PCB's, nor does he necessarily lay them out - he may have people working for him to do that. He does however design the actual circuitry and is known throughout the industry as being a genius.

It's very typical for GS people to come here and criticise whoever and whatever they don't understand simply because they can. They / you have been given an opportunity to speak your mind even if what comes out of your mind is utter foolishness.

I realise that you already believe you are an expert, but my advice is to go take some respect classes and maybe a few PCB desoldering classes, so that you may one day be able to help somebody instead of spreading arrogance and ignorance.
Old 18th February 2017
  #17
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Hear hear Mr. GM is super well regarded, ie in the top 5 in the world. To add to vitalis, pcb design plays a big role still, I'm sure the extra large ground trace is purposeful.

What I find funny is that audiospacific already gave you the answer you needed, that you need the appropriate tool for this job.
Old 18th February 2017
  #18
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Quote:
Originally Posted by Vitalis View Post
I disagree, and I bet you if I had the PCB here that I could unsolder it. Mr GM does indeed know what he's doing. It's not his job to manufacture the PCB's, nor does he necessarily lay them out - he may have people working for him to do that. He does however design the actual circuitry and is known throughout the industry as being a genius.

It's very typical for GS people to come here and criticise whoever and whatever they don't understand simply because they can. They / you have been given an opportunity to speak your mind even if what comes out of your mind is utter foolishness.

I realise that you already believe you are an expert, but my advice is to go take some respect classes and maybe a few PCB desoldering classes, so that you may one day be able to help somebody instead of spreading arrogance and ignorance.
you are totally right. sorry for my stupid post. i sat on this pcb for way too long, had a drink too much and got frustrated... sorry george i use your stuff everyday! still this is an akward pcb. hope its better on newer revisions. mine is a very low serial number

Last edited by salomonander; 20th February 2017 at 12:53 PM..
Old 20th February 2017
  #19
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alright the huge weller shovel type tip did it! anyone having the same issue, get one of those, heat the pad for 2-3 seconds and it all works as expected. thanks for the help everybody!
Old 21st February 2017
  #20
Sometimes you gotta spend some new solder, to get out the old solder.

I usually have to fill a few holes with new solder and retract it again when i put in an i.c. socket. I go realllllllllly slow, one at a time, allowing everything to cool before doing more.
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