Author Topic: Homebrew soldering iron.  (Read 2108 times)

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Offline registereduser

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Homebrew soldering iron.
« on: January 17, 2019, 07:01:23 pm »
Is there a video, blogspam article, pdf ... something that shows how to make a soldering iron with a thick copper wire tip, that works?

I watched several videos, and looked at similar articles using a wall  wart and wrapping some resistance wire around a bit of copper wire with that fiberglass insulation or whatever it is.

I tried it with scrounged bits from a heat gun that died. Not sure if the sleeve material is right, but it seemed to work,... ish, but not reliable. I hooked up to a wall wart, and tip got hot enough to melt solder. Once. Upon successive attempts it never reached temp, and the wall wart died eventually. Well, it started giving sporatic voltages. It was a 5v 2a unit. Now it is parts.

I also tried it using a little clock radio transformer that has a 20v secondary. That has a center tap for two 10v, and another secondary 10v. I only tried the 20v. Very slow to heat up, and the transformer was getting hotter than I was comfortable with.

Could I expect better results by simply getting a bigger transformer?

I've made a alcohol burner powered iron that performs better than any of the three or four cheap irons I've ever owned, but fuel costs...

I have a couple more wall warts, and an atx psu, but I'd rather not just keep killing wall warts. I tried hooking into the 12v on the atx psu, and it just instantly shuts of from overload.

Please refrain from the danger warnings and just go buy another POS advice, I've heard that already. I'm asking for help on how to build a soldering iron, not how to buy one. I'm aware that heat burn skin.

Thanks.

I should add that the application will be for raping old tvs and such, then building smoke emitters.

For clarity here's a pic of the type I've been trying, resistance wire wrapped around copper tip.

« Last Edit: January 17, 2019, 08:20:58 pm by registereduser »
 

Offline Ian.M

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Re: Homebrew soldering iron.
« Reply #1 on: January 17, 2019, 07:33:58 pm »
For a directly heated copper bit 'gun' style soldering iron, you need a lot of current at a very low voltage.   No wallwart will be suitable, and a PC PSU is likely to be too high voltage, even on its 3.3V rail. 

OTOH if you get a low voltage battery powered iron that has a proper resistance element either separate from or integral with its bit, and you feed it the same voltage as the batteries supply with adequate current capability, it should work.

If you make a single turn winding using *HEAVY* cable through a beefy enough torodial transformer or round the center core leg of a repurposed MOT with its HV secondary removed, and use a heat resistant terminal block to connect it to a hairpin shaped copper wire bit that is a small fraction of the CSA of the heavy cable, that should also work, if you nip the wire at the bend to create a higher resistance hotspot.  Control it by switching the power to the transformer primary.

If you are going to be using it much, make a jig to mass produce the copper wire bits on, as without plating to prevent the solder dissolving them, they don't last long.  If you are doing assembly work, you'll need a new bit every few hours!
 

Offline helius

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Re: Homebrew soldering iron.
« Reply #2 on: January 17, 2019, 07:38:11 pm »
The Weller soldering gun is a copper wire directly connected to a transformer secondary. The transformer ratio is much higher than you used, however, with 120V input and only 250mV output. The current through the tip is somewhere between 600 and 1800 amps. No, you cannot use a 5V 2A wall wart to do this.
 

Offline Cliff Matthews

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Re: Homebrew soldering iron.
« Reply #3 on: January 17, 2019, 07:54:02 pm »
Useful durable tips should not be pure copper, they need to be coated with what solder can 'wet' (like iron plating). Further, having a temperature controlling thermal-couple/heater combo close to the tip is important for performance, not just in controlling it, but stopping damage to delicate electronic components. If you truly don't care about wasting time on something so fruitless, disregard this and continue, but cheap durable tips that last for decades exist.. it is from these platforms you may want to start your DIY effort. Why not buy a good tip for $12 as a starting point (it's ~4.2 ohms) and you can control it by a 555 PWM'ing a MOSFET. The same can done with cheap Chinese T-12 tips, but whole thing's a $$ waist since the market has been feeding on fierce competition and slim margin's for some time.
 

Offline fsr

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Re: Homebrew soldering iron.
« Reply #4 on: January 17, 2019, 08:10:03 pm »
I have a goot branded 30w soldering iron here that i'm using since the time the dinosaurs walked the earth. Ceramic tip.
That's for general electronics. If you need to solder something heavier, you will need more power. But too big a soldering iron could fry smaller components quite fast.
 

Offline registereduser

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Re: Homebrew soldering iron.
« Reply #5 on: January 17, 2019, 09:19:15 pm »
For a directly heated copper bit 'gun' style soldering iron, you need a lot of current at a very low voltage.   No wallwart will be suitable, and a PC PSU is likely to be too high voltage, even on its 3.3V rail. 

OTOH if you get a low voltage battery powered iron that has a proper resistance element either separate from or integral with its bit, and you feed it the same voltage as the batteries supply with adequate current capability, it should work.

If you make a single turn winding using *HEAVY* cable through a beefy enough torodial transformer or round the center core leg of a repurposed MOT with its HV secondary removed, and use a heat resistant terminal block to connect it to a hairpin shaped copper wire bit that is a small fraction of the CSA of the heavy cable, that should also work, if you nip the wire at the bend to create a higher resistance hotspot.  Control it by switching the power to the transformer primary.

If you are going to be using it much, make a jig to mass produce the copper wire bits on, as without plating to prevent the solder dissolving them, they don't last long.  If you are doing assembly work, you'll need a new bit every few hours!

Sorry I guess I didn't make it clear. It's not gun type I was trying to make. Though I do want to do that also, when I can scrounge a suitable transformer. I added a photo of the type I'm trying now.

The Weller soldering gun is a copper wire directly connected to a transformer secondary. The transformer ratio is much higher than you used, however, with 120V input and only 250mV output. The current through the tip is somewhere between 600 and 1800 amps. No, you cannot use a 5V 2A wall wart to do this.

Sorry for confusion, please see above.

Useful durable tips should not be pure copper, they need to be coated with what solder can 'wet' (like iron plating). Further, having a temperature controlling thermal-couple/heater combo close to the tip is important for performance, not just in controlling it, but stopping damage to delicate electronic components. If you truly don't care about wasting time on something so fruitless, disregard this and continue, but cheap durable tips that last for decades exist.. it is from these platforms you may want to start your DIY effort. Why not buy a good tip for $12 as a starting point (it's ~4.2 ohms) and you can control it by a 555 PWM'ing a MOSFET. The same can done with cheap Chinese T-12 tips, but whole thing's a $$ waist since the market has been feeding on fierce competition and slim margin's for some time.

I've heard this before about copper being useless as a tip. I now know that this is pure marketing hype. The little iron I made that I heat with an alcohol burner wets out very well, and is not disintegrating before my eyes. It is in fact vastly superior to any of the irons (not many, maybe four) I've had so far with plated tips. I'm not using it all day every day, but from the amount I have used it I'd guesstimate it would last well beyond a month if used heavily, at a cost of IDK, 2 cents? Less? I'll take that over 15 bucks a pop every day the week and twice on Sunday.

I have a goot branded 30w soldering iron here that i'm using since the time the dinosaurs walked the earth. Ceramic tip.
That's for general electronics. If you need to solder something heavier, you will need more power. But too big a soldering iron could fry smaller components quite fast.

My end goal is to build an iron for smaller/general work and a gun for stripping parts from junk and heavy assembly. I don't by into the exotic tip hype after my success with the alcohol burner iron.

 

Offline Nerull

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Re: Homebrew soldering iron.
« Reply #6 on: January 17, 2019, 09:26:08 pm »
I can't say i've ever felt like a month was a long life for a tip, at least since the garbage copper-tip ratshack firestarter iron I had. After a few days of use there was a large hole in the tip.

I've been using the same metcal tips for years.
« Last Edit: January 17, 2019, 09:28:25 pm by Nerull »
 

Offline registereduser

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Re: Homebrew soldering iron.
« Reply #7 on: January 17, 2019, 09:51:33 pm »
I can't say i've ever felt like a month was a long life for a tip, at least since the garbage copper-tip ratshack firestarter iron I had. After a few days of use there was a large hole in the tip.

I've been using the same metcal tips for years.

"well over a month"

What I have is about 1 3/4" with the 3/4" sticking out of the coil. Had I made it 2 1/4" I'm pretty confident it would last 6 months or better with regular usage. I can't imagine someone doing electronics for a living just sits there soldering all day every day. Myself, I'll maybe spend IDK 5- 10 hours a month, wild guess. Will vary too as the urge hits and the scrounge opportunity arise.  This first tip will last me six months for sure, probably a year. Then I'll make another a little longer that will definitely last a year, basing new length on how long this one lasts.

The math does not add up to support the marketing hype. Not even close.
 

Offline jeroen79

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Re: Homebrew soldering iron.
« Reply #8 on: January 18, 2019, 12:31:53 am »
Is there a video, blogspam article, pdf ... something that shows how to make a soldering iron with a thick copper wire tip, that works?
The videos will only show you the basic idea.
If you want to be successful you need to a bit of work yourself.

-Decide what kind of power this soldering iron should have and what current and voltage you want to use.
(Ohm's law applies)
-Pick a transformer that matches these specs.
-Pick the wire you want to make the heater of. Know it's resistance per meter and it's cross section and current capacity.
-Then you can determine how much wire you need.
-For the insulator between the heater and the tip choose something that has sufficient thermal conductance.
-Then construct the iron as done in the video.
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #9 on: January 18, 2019, 01:44:51 am »
I can't imagine someone doing electronics for a living just sits there soldering all day every day.
....
The math does not add up to support the marketing hype. Not even close.

Good point, but I doubt there are many professionals that would use such a barbaric tool.  The cost of what a professional may be working on could be far more than the most expensive stations out there.

I showed some pictures of my 14 year old Pace (soon to be 15) with the original tips.  It gets a fair bit of use and the tips are still in very good condition.  Pace makes a wide variety of tips.  Trying to come up with such an assortment of homemade tips wouldn't be practical.   

I don't think the life of the tips in my case is marketing hype.  That said, I have seen some people who feel they need 1000C to solder a SOT23.  Tip is dead after a couple of uses. 

All that said, interesting project.  Look forward to seeing what you come up with.  Maybe down the road, if you end up getting a decent tool, you can make a video comparing the two.   I would watch it. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline vk6zgo

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Re: Homebrew soldering iron.
« Reply #10 on: January 18, 2019, 08:05:43 am »
People used copper tips for decades before the plated ones appeared.
Yes, they do eventually deteriorate, but they can be "redressed" with a fine file.

Unless they are abused, or are very poor quality to begin with, they won't normally have "a large hole in the tip after a few days use", but they definitely do have significantly shorter lifetimes than plated tips.

I had a very small soldering iron made by "Fairey" (not sure if it was the same company that made aircraft), when I was a teenager.

It was quite usable off a 6.3 volt "filament" transformer, but definitely lacked "grunt" when it came to large joints.
I never took the time to measure its element resistance, but my guess is, it would have been quite a bit higher than the OP's one.
The tip sat around the shaft of the iron, so it had a bit of mass to heat up, but also it didn't just lose heat when applied to the solder joint.

Nevertheless, it was a bit limited, so my next one was a thing called a "Scope" iron, which supplied a lot of current to a carbon rod which contacted the back of the tip when a control ring around the iron handle was pushed.
These were used for just about any conceivable job, with larger or smaller tips & manually controlled "on" time, depending on the job.

There are still some godawful things masquerading as soldering irons.
Foremost among these are the allegedly adjustable ones which just have a mains operated iron fed through what is basically a "light dimmer", using an SCR or TRIAC.

You wind the pot up, & they become  too hot. Wind it down, & they become too cold.
The tips have a very short life.
After my Weller WTCP croaked,  I picked one of these things up from Jaycar to "get me out of trouble" till I fixed it.

Well, it was a nightmare to use, but I did do a few joints OK, after I developed the right technique.
Wondering why it was so lousy, as the base seemed quite heavy, as if it had a reasonable transformer, I opened it up, & was confronted by the previously mentioned "light dimmer".
The reason it was heavy was a weight glued to the inside bottom of the case. :palm:

To the OP, I would suggest picking up a secondhand WTCP, as it will do most of the work you need to do.
You are then free to experiment with homemade irons without needing them to be useable in the short term.

By the way, you mentioned using a small iron with a spirit lamp.
Have you thought of trying a gas soldering iron?
They will work outdoors, & are reasonably economical, probably better than your spirit lamp setup.
They would certainly be more convenient.

 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #11 on: January 19, 2019, 12:22:22 am »
I'm asking for help on how to build a soldering iron, not how to buy one.

.....
My end goal is to build an iron for smaller/general work and a gun for stripping parts from junk and heavy assembly. I don't by into the exotic tip hype after my success with the alcohol burner iron.

Let's say I wanted to make an iron to work on what I would consider smaller general work.  I will want something that can reach around 620 F.   I want enough heater to to keep up with a somewhat large load, say maybe 40 Watts. 

I started by selecting a decent tip.   Of course, I went with Pace.   I want to keep the heat in the tip and use some ceramic to insulate the tip from the handle.   I cut the tip and thread it into the ceramic with a bit of Kapton to help prevent it from chipping.  Kapton is good for over 700F.
« Last Edit: January 19, 2019, 01:58:49 am by joeqsmith »
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #12 on: January 19, 2019, 12:29:48 am »
Next we need some sort of heater.  I will use some NI80/CR20 28AWG.  This is spec'ed at 4.094 ohms/ft.   I want to be able to run it from a 24V source.   I spool off a bit over a foot and measure 4.9 ohms.   V^2/R or 24*24/4.9 = 117Watts.  I will never run it up this high but should give me plenty of heat to ramp it up fairly fast.   I need some sort of a temperature feedback and I also want the tip grounded.  Time to kill two birds with one stone and add a K-type.   Wires used to power the heater will need to handle a bit of heat and are Teflon jacketed. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #13 on: January 19, 2019, 12:32:43 am »
A layer of Pyropel is then placed over the heater.  I'm ready to see how fast it ramps and lay it on a brick for testing...
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #14 on: January 19, 2019, 12:37:36 am »
After a bit of testing with the bench supply, it looks pretty good. I let it cook for a while at 630F.  This is a bit higher than Pyropel is rated for. 

I let it cool and then wrap a second layer of Pyropel over the entire assembly and tape it up with some 3M aluminum foil.  Time to give it the hand test...

Now the people that seem to make these crude tools always seem to use some POS handle.  Many seem to be proud they have used an old pencil.   I think I want something a bit nicer.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Cliff Matthews

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Re: Homebrew soldering iron.
« Reply #15 on: January 19, 2019, 01:22:56 am »
Pyropel must be expensive stuff.. any chance of getting this in the ops home country? (YouTube shows India)
https://www.foundryservice.com/product/pyropel-rigid-and-flexible-600of-polyimide-fiber-insulating-boards-felts/
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #16 on: January 19, 2019, 01:55:47 am »
Pyropel must be expensive stuff.. any chance of getting this in the ops home country? (YouTube shows India)
https://www.foundryservice.com/product/pyropel-rigid-and-flexible-600of-polyimide-fiber-insulating-boards-felts/

It's not good enough really for this application.  They really need to hunt down something rated for higher temps that is available to them. 

Standoff soldered in the end of a 25-06.  A 35 Remington soldered to the backside for length.   I like Beringer and keep a few corks on hand.   Time to try some UNI-T soldering.....
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #17 on: January 19, 2019, 03:03:43 am »
The next step would be to close the loop.  For a simple test, I could use the PC with Labview to run a simple PI control.   

Bottom line, it's not something I would recommend spending time with.  My hobby iron is not real high end.  As I mentioned, it's almost 15 years old.  Still has all the original parts.  It sees a fair bit of use.   Figure what I paid for it all those years ago, cost per year ownership is way less than what people would spend on coffee or the pub.   I solder enough that I want a decent iron and this crude device will need more time put into it just to get it usable. 

First time trying it, running open loop with a constant current source (bench supply).   

https://youtu.be/7XXhsVnH6sE
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #18 on: January 19, 2019, 03:07:39 am »
Looks like YT is still crunching it for the higher res...   Maybe wait a while.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #19 on: January 19, 2019, 03:25:09 am »
Ceramic fiber seems like a better choice.   I use something like this on my race bike for the exhaust and it would easily take these temperatures.   

https://www.ebay.com/itm/Fiber-Blanket-High-Temperature-Insulation-Refractory-Fireproof-Cotton-Blanket-US-/173719479418
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Cliff Matthews

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Re: Homebrew soldering iron.
« Reply #20 on: January 19, 2019, 05:21:07 am »
Ha! Joe's number one with a bullet!  :-DD  Are you sure you're not actually working for Pace in another universe?
 

Offline Ian.M

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Re: Homebrew soldering iron.
« Reply #21 on: January 19, 2019, 12:43:38 pm »
Fiberglass surfacing tissue, which is a 'felt' of fine glassfibre is readily available.  Use it with fire cement and you should be able to assemble a suitable refractory heater element without relying on exotic high temperature plastics or the availability of a good enough grade of sheet Mica that can be split thin enough to wrap round small cylinders.   However I question the wisdom of assembling the element directly on the bit.  Surely it makes sense to use a close fitting metal tube or sleeve on the bit with some means of clamping the bit in it, and winding the element on the sleeve so the bit can be replaced?

An interesting project would be a temperature controlled soldering gun with a thermocouple in contact with the back of the tip held in place by something like a thin crimped anodised aluminum sleeve. The transformer core could be built of stacked ferrite rings, and a push-pull SMPSU controller + power MOSFETs used to drive it.

Bonus points if you also make a hot air tip for it - a short coil of wire as the heater stuffed with rockwool as a diffuser, with the thermocouple running through the middle of it with the junction at the tip end, then more rockwool round it, inside a thin walled steel tube long enough that the gun end remains cool enough to connect to an airline, with a regulator to provide flow control and a solonoid valve controlled by the gun trigger.
« Last Edit: January 19, 2019, 12:51:45 pm by Ian.M »
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #22 on: January 20, 2019, 02:08:50 am »
Ha! Joe's number one with a bullet!  :-DD  Are you sure you're not actually working for Pace in another universe?

For work, I've used Pace for  many years.  At home, I have used various brands but I have seen very little problems with Pace and eventually changed when my last Wellar station died.   I am waiting for their tweezers like everyone else. 

Quote
However I question the wisdom of assembling the element directly on the bit.  Surely it makes sense to use a close fitting metal tube or sleeve on the bit with some means of clamping the bit in it, and winding the element on the sleeve so the bit can be replaced?
That's pretty much how every iron I have had at home works.  At work I use the Intellaheat which has the heater integrated into the tip.  When the tip is shot, you replace everything.   For this iron, the fact that most videos show using a pencil for a handle, no feedback.... I doubt they are thinking they need something that advanced.   As the OP posted, a hunk of wire for the tip is pretty cheap. 

For the project itself, I question the wisdom of rolling your own.  I doubt I could make something as nice as what it offered without spending a fair bit more money.   Maybe you could roll your own and post is here.  I'm sure the OP would appreciate seeing something more professional than my minimal efforts.



This is the material I use on the dragbike to wrap the turbocharger.  Things get much hotter than a soldering iron.   I unwrapped it and installed this along with some higher temperature wire.   I ran it up well above where I would normally use an iron and just let it set.  No more smoking Pyropel.     

I also used a copper ring and crimped the TC very close to the tip.  If I decide to run it closed look, it should help with the controls. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Homebrew soldering iron.
« Reply #23 on: January 20, 2019, 03:43:58 am »
Just using Labview to control the bench supply to close the loop.  Quick and dirty.  Gain is up a bit too high but it's way better than it was running open loop.

The dips are soldering a large section of PCB.  It's not the right tip for it but it does add a fair bit of thermal load so I could watch the response. 
« Last Edit: January 20, 2019, 03:49:35 am by joeqsmith »
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online james_s

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Re: Homebrew soldering iron.
« Reply #24 on: January 20, 2019, 04:02:18 am »
Is this a "because you can" type of thing? Because I can't think of another reason to build a soldering iron from scratch. There's no way it will work as well as even a basic off the shelf soldering station. Regarding tip life, I recently replaced the tip on my Edsyn iron which I had been using for at least 15 years with the same tip. Properly cared for, the tip on a temperature controlled iron should last a very long time.
 


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