I have a 100 W soldering gun with a 20% duty cycle but I'd like to use it more often than 12 seconds in every minute so I was wondering whether I could modify it to incorporate a fan I salvaged from a laptop. The fan is designed to blow air in a sort of channel which could fit right on top of the gun. My problem is how to power the fan. It requires 5 V and I'm not sure what the second coil of the gun produces. There's a small amount of space in the handle where a switched mode power supply could potentially fit? I think the fan could just run constantly whilst the gun is plugged in.

 

does it actually overheat after 12 seconds?

What are you doing with it that needs the extended duty cycle?

With many of those basic buzz gun (transformer based ) soldering guns a simple trick to getting way more run time from them is to switch to a smaller more efficient tip assembly which may mean either simply using one designed for another gun or making a homemade unit that best matches your guns output voltage and current characteristics.

I have a old craftsman 100/140 watt buzz gun that when I first got it was junk being the gun would overheat about as fast as the soldering tip did due to the tip having far too low of resistance for its design, which BTW its internal design is very similar to yours and came with a tip similar to what you have, I switched it over to the 100 watt tips that radioshack used to carry. These, https://www.amazon.com/Weller-8125W-Replacement-Soldering-Gun/dp/B00018APQU and never locked back.

Whole new gun and performance curves just by changing tips!

 

I can't imagine a 20% duty cycle in a soldering gun! It must be more like 1 minute on and 4 minutes off because my 100 watt Weller is just about up to temperature in 12 seconds.

Meanwhile, pounding a tip out of some 10 ga copper wire seems like an easy enough job. It's those pesky attachment points that always seem to interfere. I have to clean them up every time I haul ol' betsy out.

 

I can't imagine a 20% duty cycle in a soldering gun! It must be more like 1 minute on and 4 minutes off because my 100 watt Weller is just about up to temperature in 12 seconds.

Same with my Craftsman with the undersized tip. 4 - 5 seconds tops to get up to temp then manual PWM to keep it there and I have yet to ever find a soldering job that was big enough to overheat the transformer including hand reflowing 3/4" wide circuit traces on high powered power inverter and car audio amplifiers.

Anything above that is butane mini torch with a soldering head adapter or full on propane torch with an open flame type work.

 

I have a propane (or Mapp gas) soldering tip from about 30 or 40 years ago. Just the thing for battery cables on a car!
Everything from a $10 hair dryer (for heat shrinking) to oxy-acetylene in my shop.
Still haven't figured out how to stick weld with lead solder.

 

I think you will find it's just too annoyingly inconvenient to try to power the fan.

A wall wart and an extra set of wires would be the simplest and safest, but my my, what an ugly mess.

 

I think you will find it's just too annoyingly inconvenient to try to power the fan.

A wall wart and an extra set of wires would be the simplest and safest, but my my, what an ugly mess.

The problem with the fan is its unlikely to draw off enough heat to give any measurable run time gains for the added gear. If the gun is overheating in 12 seconds something is seriously wrong with it already because of the wrong tip or the windings have already been overheated and now have a partial short or it's just that cheaply built.

My guess is that either the tip has really bad connections with the gun and they are heating things up, as #12 has implied happens with his gun and I know my old Weller has that issue from time to time as well, or it's already been overheated so many times the transformer and windings are cooked and the gun is basically junk at this point.

 

Never used such a soldering iron. My iron of choice was a 240V fed "tubular" type with a small microswitch bimetall temp control built in. I now have a electronic controlled iron with temp setting. works well for me.

 

The instruction to use it no longer than 12 seconds in every minute came from the manufacturer, Weller. It's in the manual and on a label on the gun. I figure there's probably some engineered margin in there, especially when using the gun from cold but still, I don't want to risk my gun (my previous gun came with no such warning and I destroyed it because I had no idea this was an issue). There's not really any way for me to determine how close it is to overheating so all I can do is err on the cautious side.

I've ordered a switched power supply (30mmx20mmx18mm) that I should be able to fit into the handle.

 

...And then there is this...

https://www.digikey.com/product-detail/en/cui-inc/PBK-5-12/102-3114-ND/4332651


Edit- Ok it's a gyp, after reading the data sheet- it requires all kinds of external components to work, so it's not really as "small" as I thought.

 

If you are doing so much heavy soldering as to be able to burn out a gun such as that you are in the realm where a butane or propane torch system should be being used.

If you are just concerned about burning up the gun addings simple thermal switch that shuts it off when it does gets too hot would be far more realistic.

 

If you are doing so much heavy soldering as to be able to burn out a gun such as that you are in the realm where a butane or propane torch system should be being used.

If you are just concerned about burning up the gun addings simple thermal switch that shuts it off when it does gets too hot would be far more realistic.

What would I use for the thermal switch? Any idea where best to place it? Maybe on the inside of the secondary coil? Also, what temperature would be the threshold?

Recently I've been using the gun to salvage components from some scrap electronics. I used the gun to minimise the time I had to spend heating them.

 

The instruction to use it no longer than 12 seconds in every minute came from the manufacturer, Weller.

I just took Weller off my list of things to trust...or buy.

 

If you are going to do electronic work I would advise getting a temperature controlled soldering iron. The hot wire guns are ok for working on cables and such but keep them away from PCBs.
Many years ago I used a Scope iron. It has a 2.2V (I think) high current transformer and a carbon block heater that slid up to touch the tip to turn it on. The 12V versions ran with a long lead to be the dropping resistor. (A quick check shows they are still available.)
Very quick to heat but quite lethal to circuit boards particularly in the hands of a novice. It took me a while to get adjusted to their use.
A red hot tip is not good for a lot of work but you can use silver soldering rods with them.
I would think the hot wire ones will be similar, but maybe not as hot.

I have seen a lot of boards damaged buy high temperature.
Good tools are a great asset, and make your work a lot easier. It is handy to be able to adjust to a known and controlled temperature.

 

I just took Weller off my list of things to trust...or buy.

I just consider such things and safety awareness recommendations where real life operation or modifications or gross lack of proper service to the device may result in substantially different run times than what is listed.

I know that with my old weller that if the connections between the gun output bus bar lugs and the tips are not kept clean and tight it seems to put a lot more heat into the the gun than it does the tip thus resulting in pretty poor run time to working time ratios.

 

EEK! I have an old maybe 100/140 W gun (Weller 8200). I haven't used it in eons. I got a self-igniting Master Ultra Torch that I use for big stuff.

I'd like to have a resistance soldering system (American Beauty) like I had at work. It's great for pins.

 

That iron is why you burned the pads off that board you were attempting to "repair"..
I would never consider using one of those for electronics soldering.. Repairing stained glass/burning wood/plumbing.. sure.. electronics heck no...

As stated above get a proper temp controlled soldering iron (and hot air if you want to do surface mount)

 

That iron is why you burned the pads off that board you were attempting to "repair"..
I would never consider using one of those for electronics soldering.. Repairing stained glass/burning wood/plumbing.. sure.. electronics heck no...

As stated above get a proper temp controlled soldering iron (and hot air if you want to do surface mount)

I was not repairing the board; I was salvaging components off it.

I don't think a temperature-controlled soldering iron is necessary at all. I've been using a 25 W and a 30 W iron for years with no major problems