Best way to remove transformers that are glued to PCB?

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Lee_M

Well-known member
Joined
Nov 23, 2013
Messages
309
Location
Dorset, UK.
Hey guys,

Hope everyone's having a good weekend!

The title says it all really, I've picked up some transformers that are both soldered and glued to PCB's and I've been having a hellish time trying to remove them.

Has anyone got any tips or tricks for freeing them from the boards?

Thanks in advance,
Lee
 
If the board doesn't care too much for you I'd start tearing it apart and then unsoldering pad by pad and take care of the glue by it self, maybe some heat helps, depends on what is the glue like and where it's glued you could use some solvent also...

JS
 
Most glues will let go if you de-solder by hot air (which also heats PCB area around component)

Heatgun will do if you have good ventilation.

Jakob E.
 
Thanks for the replies.

I haven't got a heatgun, desoldering iron or anything like that yet (Been using a cheap iron and a solder pump, For now) but I may have to invest in one if it's going to make this process much easier.

What kind of solvents would you recommend? Whats the best way to apply them?

I've got some "Goo be gone", Which I believe is mostly D-limonene. Would that be much use?
 
I'd try with heat first, even boiling water works in some cases. The problem with solvents is they may damage the coating on the lamination if it gets into it, which is not a good thing. If you find a way to apply heat to it may be the way to go, I don't know how much glue do you have or how exposed it is. As I said, breaking the board apart with some not so light tools may help.

A picture of it may help us to get a better picture of what you are trying to do here...

JS
 
Ok, I just ordered a heatgun from ebay. I'll wait and see how I get on with that.
I'm definitely going to pick up a proper desoldering station soon but funds are tight at the moment.

I'm basically trying to remove Lundahl LL1540's from some old broadcast PCB's, Which are being scrapped once the transformers are removed. They don't have a lot of glue applied...Just enough to make it annoying! I haven't got a camera to hand but can dig it out if it'll help.
The first one I removed took about half an hour of soldering and prising, But it worked out okay in the end. The second took a little bit less time but I seem to have damaged it during removal as both of the secondaries test as "open circuit" on my multimeter.  :'(

After that I panicked and decided to start this thread...I've got another 12 transformers on pcb's, waiting to be desoldered.
 
I think the problem I'm having is not exactly knowing where the solder ends and where the glue begins!
I removed everything I could see on the "track side" of the first PCB that I was stripping down, but it's impossible to tell for sure if I've got it all.

I've removed a fair amount of transformers from various PCB's without hassle, Even with my humble setup, But these LL1540's are giving me real trouble.

Would something like this be a worthwhile upgrade from the hand solder pump I'm using currently?
http://www.ebay.co.uk/itm/30W-220V-50Hz-Electric-Vacuum-Solder-Sucker-Desoldering-Pump-Iron-Gun-/360905403963?pt=LH_DefaultDomain_3&hash=item5407a36e3b

If not, Can you recommend a better alternative that won't cripple my finances?
I'd love to get something professional, like one of the Hakko units but I can't justify the kind of money they go for, At least not right now.
 
As I already said I'd cut the boards with a dremel tool or something like that, so you can desolder the pads and remove that part of the board and then fight against the glue with no risk of breaking the pins or connections.

For desoldering some desoldering wick should help, I don't know if you are using it, I don't have a lot of trouble desoldering stuff with the pump to remove most of the old solder, then applying little new solder and proceeding with the wick. You need to add a bit of solder to the wick to work properly and removing most of the old solder from the board with the hand pump and then using a drop of new tin helps a lot. The wick sucks the tin to the point it's completely dry and you just just pick the component from the board.

JS
 
I've tried using a combination of solder pump and solder wick to remove the solder but it's still not going smoothly, I'm a bit  concerned my hand pump may be on it's way out so I've ordered that desoldering gun that I linked to in a previous post and will wait until that arrives before attempting any more.

The thing is, I've desoldered probably 30+ Lundahl transformers from various boards over the past few months and all of the others have been a breeze. None of the previous PCB's had the transformers glued to them, It was just a case of placing the board upside down in some helping hands (with pins facing up) and desoldering each pin until the transformer pulled itself out with it's own weight.

Regarding solvents, What kind of stuff should I be looking for and what's the best method of applying it without risking damage to the transformers?

The glue is barely visible, It's sandwiched between the TX and the board. The clearance between the two is minimal, Although I've had some limited success with scraping a stanley knife underneath to painstakingly clear some of the glue.
Should I try dipping the blade in some solvent?
 
Maybe heat the blade or a cheap fillet knife might provide more reach.

You can also probably cut away the PCB around the circumference of the TX to get a better angle. If you don't need the PCB that is...

Cheers!
-jb
 
If the board is plated through get yourself a proper electric desoldering pump. I was a bit like you, used a mechanical desoldering pump for tens of years without any problem. Until a couple of years ago when I botched a pair of Lundahl.

In terms of glue, it all depends what type of glue it is. But generally it will be solvent based something like Fastbond.  Probably it is also glued after the transformer had been soldered onto the board. In which case Get yourself a good scalpel. I have been using this for 35 years now;

http://www.scalpelsandblades.co.uk/range_14_swann-morton-non-sterile-surgical-blades-and-handles--no-3-fitment.php

Cut the glue around the transformer and inject some cigarette lighter fluid. Repeat a few times if necessary.

If it is giving you the static (borrowed from Reservoir Dogs)  inject some chloroform or dichloromethane. It will turn into a soggy bag of chips. Be careful with these. Use them in a well ventilated area.
 
Thanks for all of the suggestions! They are all appreciated.  :)

I'm waiting for that electric desoldering pump to arrive before I proceed, I figure it's not worth risking damage to any more.

I've been trimming the boards down for easier access but the troublesome part is working with the tiny amount of clearance between the board and the tx, It's tricky even getting a blade in there in some cases . The blade I'm using has enough reach to get all of the way under the TX, When the clearance is enough, But it's a "box cutter" type blade and isn't very sturdy.

I'll try the heated blade approach (maybe not with the box cutter, not sure the plastic handle would be too happy with that!) and then carefully apply some lighter fluid. I've got some IPA on hand, Would that be worth using?

Sahib, Do you mean naphtha based fluid? I'll try the other suggested methods before I start looking into procuring chloroform.
Regarding the Swann Morton scalpels, Would the "No.3" handle and size "10a" blades be useful for what I want?

mjrippe said:
Sell a few of those Lundahls and buy the Hakko.
The chance would be a fine thing! Anyone interested in any LL1540's still mounted on PCB's?  ;D
 
No 3 handle will take 10A blade.

You can also get No 4 handle that takes larger/longer blades like 25A and 26. Be careful with 26 though, it is like a machete. But it is longer which can travel under further.

When using these blades, particularly for trying to prise things out please wear eye protection. They can break and spring off.

Chloroform will dissolve acyclic based plastic. Dichloromethane will dissolve acrylic but also polycarbonate. Tetrahydrafureane will dissolve PVC.

Part of my business used to be in modelmaking  so these are the chemicals that we used to use for sticking plastic materials. I suffer from migrane terribly so I stopped using Chloroform about 25 years ago.

If you can not get these Evo-Stik Adhesive Cleaner will also help dissolve it.  All you may have to do is to apply a few times.

The good side of these chemicals is that they evaporate pretty quickly, including the cigarette lighter fluid. 

Just as an additional info, you can use  dichloromethane for removing paint. Cigarette lighter fluid is also good for cleaning surfaces off grease, glue etc. 
 
Thank you very much Sahib, That's lots of helpful info!  ;D

I think the No.3 handle/10a blade combo should be a good starting point, I don't generally find myself using blades too often but I'm sure it will come in handy once I have a good one.
Point taken about the eye protection, I'll make sure my goggles are on.

Is D-Limonene (Goo gone) likely to be useful for this? I have a bottle of that on hand.
If not, I'll probably give the lighter fluid or Evo-stik adhesive cleaner a go,  As those are easily and locally available.
 
You are welcome.

Set of surgical blades like that will always come in handy.

I did not know what D - Lemonene was and have just looked up. Below is from Florida Chemical Company web site

.....As a straight solvent, d-Limonene can replace a wide variety of products, including mineral spirits, methyl ethyl ketone, acetone,..........

This is interesting. Acetone is also a good remover. So it may work.

I am not sure where you are located but I have just googled and you can get all of these even off e-bay.

http://www.ebay.co.uk/itm/like/281634652537?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

 
Success!
That electric solder pump arrived today, Worked like a charm for removing every last bit of solder from the pins. Then a little lighter fluid combined with my stanley knife took care of the glue.

Managed to remove 3 transformers (all tested perfect!) in about 10 minutes or so, But then my brand new solder pump started making a quiet popping sound, followed by a very loud pop and then it died completely!
Top quality chinese craftsmanship, I guess.  ;D

At least I've got some of the Lundahls off the boards, They should keep me busy for now.
Going to get a replacement electric solder pump and hope I just got a duff one.

Thanks for all the help, Guys!
 
> PCB's ... are being scrapped once the transformers are removed.

Is this for re-sale?

If own-use, why bust them off the PCBs? Saw around the iron, and butt-solder your leads to the PCB pads. Won't be much bigger than the naked iron. May be more robust against lead pull-out.
 

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