# Deception In Soldering Iron Ratings

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#### MrAl

##### Well-Known Member
Hello there,

QUESTION #1:
You are shown two temperature controlled soldering irons, one is 60 watt and one is 40 watt. The 60 watt iron is slightly more expensive than the 40 watt iron, but not much more. Which one do you purchase?

QUESTION #2:
You are shown two temperature controlled soldering irons, one is 60 watt and one is 50 watt. The 60 watt iron is slightly more expensive than the 50 watt iron, but not much more. Which one do you purchase?

QUESTION #3:
You are shown two temperature controlled soldering irons, one is 60 watt and the other one is either 40 or 50 watt. The 60 watt looks a little cheaper in quality but not too much cheaper. Which one do you purchase?

If you answered "The 60 watt iron" to either question above, you probably paid too much for that iron because guess what, they are all about 40 watts !!

In various ad's on the web we see 60 watt irons that are the exact same model as the 50 watt irons, yet they are both really only 40 watts. This means they cant solder as well as a real 60 watt iron for somewhat larger metal joints.

First we see the 60 watt rating, which appears in ads for companies that dont seem to care about what they say about their product as long as it sounds good. Then we see the 50 watt rating, where the company is a little more responsible about their rating because they take their rating directly from the heating element which is stamped "50 watts, 24 volts". So we cant blame the companies that advertise 50 watts.

Measuring the DC resistance, we see that the "50 watt 24 volt" element resistance really measures 16 ohms. The power delivered to a 16 ohm resistance with 24 volts DC is:
P=24^2/16=36 watts.

So the elements are not even up to 40 watts yet !

The way it looks is every time the product changes hands the receiver tacks on another 10 watts, so that by the time the ad gets posted it's up to 60 watts in some cases.

That's quite deceptive because we purchase items based on what we need, and sometimes we need the higher power iron but we dont get that, when if we knew the actual rating we would get one that really fit the job.

You'll note that many soldering stations use AC not DC, but that only makes matters worse if there is any inductance because that can only lower the wattage not increase it.

One manufacturer that was contacted actually said that the "60 watts" came form the "input power to the station". But that's not accurate either because the input power with only the iron running is not anywhere near 60 watts. It's also very unlikely that a small control board and transformer would consume 20 watts of power when powering a 60 watt device on full power.
When informed about this, they simply state that you can return the entire station for a refund.

Please note that this doesnt mean that the irons dont work at all, they do, but they wont be as high powered as expected. For example, i had no trouble soldering a #24 gauge (AWG) copper wire end to a 10 turn Bourns potentiometer terminal, which is about 1/8 inch wide and about 1/8 inch long and thin metal. Didnt try #12 AWG wire yet though.

If you have any comments that would be nice to hear, or if you have any experience with these irons. The elements themselves are often advertised as "50 watts 24 volts DC".

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#### JimB

##### Super Moderator
Thought provoking MrAl. So much so that I gathered up all my soldering irons and did a few tests.

I measured the resistance of the heating element, hot and cold, and calculated the power at both maximum and minimum rated supply voltages.
The results are presented in the table below.

The Antex iron is a simple 15watt iron which always surprised me how well it would deal with large joints and chassis connections when the large (6mm) tip was fitted. This iron dates from the early 1970s.

The two Oryx irons are nominally identical and are temperature controlled and adjustable by means of a screw in the side of the handle.
The tips are easily replaceable and I only "retired" this as my everyday iron when the tips wore out and seemed to be unobtainable. I have recently found a source of tips and have a few on order so that I can use the iron out in my garage with out having to come into the house to borrow the Weller.

The Weller is the old faithfull TCP type as used by Audioguru when he installed the sound system on the Ark for Mr Noah.

The Solon is a large heavy duty iron for soldering big lumps. The actual iron belonged to my father and probably dates from the 1970s, but, it is identical to an iron which he had in the 1950s which presumably failed at some time.

JimB

#### audioguru

##### Well-Known Member
Noah's Ark sank because my soldering made it too heavy to float anymore.

My "50W" Weller soldering iron is mostly used for soldering small wires to a pcb or slurping up solder to remove a part that has small wires. But sometimes I replace its 1/16" chisel tip with a much larger 1/4" blade (like a screwdriver blade) that takes some time to reach a proper temperature but it is large enough to hold the heat long enough to solder or desolder something that is pretty darn big.

My 50W soldering iron does not heat the room with 50W all the time like a cheapo soldering iron with no temperature control. It might idle at 5W. It goes to full power the moment it needs more power.

#### MrAl

##### Well-Known Member
Thought provoking MrAl. So much so that I gathered up all my soldering irons and did a few tests.

I measured the resistance of the heating element, hot and cold, and calculated the power at both maximum and minimum rated supply voltages.
The results are presented in the table below.

The Antex iron is a simple 15watt iron which always surprised me how well it would deal with large joints and chassis connections when the large (6mm) tip was fitted. This iron dates from the early 1970s.

The two Oryx irons are nominally identical and are temperature controlled and adjustable by means of a screw in the side of the handle.
The tips are easily replaceable and I only "retired" this as my everyday iron when the tips wore out and seemed to be unobtainable. I have recently found a source of tips and have a few on order so that I can use the iron out in my garage with out having to come into the house to borrow the Weller.

The Weller is the old faithfull TCP type as used by Audioguru when he installed the sound system on the Ark for Mr Noah.

The Solon is a large heavy duty iron for soldering big lumps. The actual iron belonged to my father and probably dates from the 1970s, but, it is identical to an iron which he had in the 1950s which presumably failed at some time.

JimB

View attachment 89565

Hi,

That's a very comprehensive table there Jim, thanks for posting that.

#### MrAl

##### Well-Known Member
Hi,

I just measured my Ungar (remember them?) iron rated for 45 watts at 120vac 60Hz. The cold resistance measured 240 Ohms which comes out to 60 watts at 120v, so the resistance probably goes up a bit when it gets hot (i didnt not measure that yet). But im sure it will fall within a reasonable range of power near 45 watts because their irons were made pretty good. That thing might be from the 1970's ha ha.

Anyway, if there is a diode in your iron then it most likely is there as part of the overall design. If it is there permanently and not part of a hi/lo temperature switch, then that means the element would get too hot without it. We dont know why they did this yet and it could be because they use the same element in another model iron or they just found that it gets too hot without it. We'd have to ask them.
It is true that if you double the voltage you increase the power four fold, so using a diode would then just double the power which would bring it up to 50 watts. Maybe it could handle that, maybe not. Maybe they use that same element with a temperature controlled station which wont apply the full 220v to the iron constantly but will only supply that power if the iron cools down slightly due to a thermal cooling sink (a large joint). That would mean that if you short the diode it could burn up after a while if left on when not in use. That would also mean that if y ou could rig up a temperature sensor you could vary the temperature with a control circuit and get a higher power iron out of the deal without burning up the element. This is just a guess though because we dont know the real reason why they used the diode for sure.

It is good to know the power of your soldering iron so that you know what you can and can not do with it. 36 watts is good for small stuff like DIP packages and transistors, but wont work well with larger joints with heavier wire. It is also important to know the spec when you go to buy one so you know what you are getting so you know what you can and can not do with it.

#### throbscottle

##### Well-Known Member
Reminds me of a portable cd/radio an ex-boss raved about with some ridiculous "power" on the box, might have been 100's of watts. You'd have been lucky to get 10w out of it (probably with massive distortion). Interesting how mfr's just pluck magic figures out of the air. Question everything!

##### Well-Known Member
Thank you Al for what is proving to be a very enlightening thread. So sitting here with one of my inexpensive soldering pencils, inexpensive is a nice way to say cheap. This is labeled Radio Shack and has a selector switch for 15 Watt or 30 Watt. So I place it in the 30 watt position and I read ~479.5 Ohms, I reverse my ohmmeter leads and read 479.5 Ohms (same reading). I select the 15 Watt position and read open circuit on my Fluke 87 but when I reverse the leads I read ~256.8 Ohms. My guess would be there is a diode lurking about in there.

Ron

##### Well-Known Member
Reminds me of a portable cd/radio an ex-boss raved about with some ridiculous "power" on the box, might have been 100's of watts. You'd have been lucky to get 10w out of it (probably with massive distortion). Interesting how mfr's just pluck magic figures out of the air. Question everything!

Popular during the 70s. A 200 Watt (per channel) stereo amplifier in reality could be a 70.7 watt stereo amplifier. Wow, 200 watts of booming peak to peak power!

Ron

#### throbscottle

##### Well-Known Member
This was mid-noughties, and even peak to peak wouldn't meet the power stated on the box. Crazy.

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