Seeking advice on new iron/handle for old soldering station (thermocouple sensor type)

First post here, so hopefully this is an appropriate post for this section :slight_smile:

I have an old soldering station (Micron - pre 1990s) that needs a new iron (lack of tip availability, corrosion of original sleeve). The station belonged to my grandfather and is something of a sentimental piece, so I’d love to get it back into action. Will be soldering mostly through hole, and some SMD (SOT23).

The heater element measures 12 ohms (heater) and 1 ohm (thermocouple sensor). Supply from station is 24V AC, and the old handle states 48 watts.

I’d love some suggestions on what would be a good compatible replacement handle with compatible thermocouple sensor-based heater, and the resistances of my original iron.

What would be a good bang for buck iron, with good tip availability that would fit my station? Can I get something decent for 50 bucks or less? I’ve looked around, but am a bit lost at this point.

Any advice would be greatly appreciated!



Hi Nick
Does this iron have some sort of plug on the cable and if so do you know what it is.

Weller irons used to be 24VAC but I don’t know what the modern ones operated at. The temperature control used to be a magnet in the tip so to change temperatures you changed the tip.

Does your old station have a model number? There might be some info still available from that.

You would have to know what type of thermocouple. Probably “K” type. Is the thermocouple wire coloured like red and yellow covering on the wires.
Cheers Bob


Hi Nick,

Bob is on point, we need a bit more information to move forward here.

1 Like

Thanks for your replies guys.

Bob, there is no plug. The iron is hard wired directly into the station. Date of manufacture looks like mid 80s.

The thermocouple wires are yellow and black. Given the unit was made locally by a company now defunct, and its age, I doubt they bothered following colour coding conventions. But I could be wrong.

Model is a Micron W/2172 (CAT T2440). I’d upload a pic, but am not sure how to.

Thanks again ! If there’s other info that will help, let me know. Cheers - Nick

1 Like

Hi Nick

In fact they would probably be more likely to follow colour coding conventions than today.
BUT the colour of the thermocouple wire covering in fact signifies what type of thermocouple it it.
Following is a screen shot from This web site


Which suggests the only Black and Yellow listed to be the French system for “J” type.

Please make sure of this as the more normal “K” type has Red and Yellow and there is a possibility the red could appear black over time.

A trip to that web site will provide lots more information.
Cheers Bob

1 Like

Hi Nick
This might interest you.

To be a direct replacement you need one that operates with the same type of thermocouple. The Hakko and others seem to operate with a thermistor which is a different beast.
Trouble is when you start talking decent quality temperature controlled soldering irons you are also talking $$$. I don’t think there is any way around that.

If the heater part of the original iron is still OK have you investigated using Hakko tips. I was using Hakko tips on a “Goot” soldering station with success until I decided to purchase Hakko as an upgrade. Nothing really wrong with the Goot though except the larger footprint.
Cheers Bob

1 Like

Hi Bob, thanks for getting back to me with that information, very helpful !

I should clarify regarding the colour of the thermocouple wires: The wires coming from the element itself, for both heater and thermocouple, are all plain white. The wires leaving the termination board in the handle have the colours (yellow/black, thermocouple; red/white, heating element). The red and white are definitely the heater, as I measured ~24V AC on them whit the iron on.

The polarity of the yellow and black is the opposite to the French J-type shown in the chart (yellow goes to the “-” on the termination board in my handle). So I’m not sure there.

I took a voltage reading of the thermocouple after ice bathing it (cold junction reference) and then dipping in boiling water. I got 3.9 mv, which for a K-type would be 96C. I live at 500m, and water boils here at 98, so that’s pretty close.

I did see that article on the conversion! Thank you for digging it up. yes, it seems lots of thermistor-based handles out there. Supposedly the A1322 heater elements are thermocouple-based though, so I’m looking down that path. Some handles are so cheap, it might be worth a punt, along with some heater elements to try measuring. What do you think?

Unfortunately no tips fit my iron at all it seems, based on my searching, hence the quandary I’m in. The heating rod has an OD of 5.5mm, which is way thicker than any modern tips I’ve seen will accept. They all seem to be <4mm ID. The handle + element is otherwise totally fine, sans tips.

Thanks for all of your feedback. The search continues!

Hi Nick
Yes, the voltage you measure certainly indicates K type thermocouple. I would not take too much notice of the odd fraction of a mV you measured. After all you are only a few µV short of 98ºC. Your meter could be that far out. I don’t know but I would guess the calibration status of your meter would be unknown as is most home instruments.

The actual thermocouple wires should be Red (-) and Yellow (+) in a brown outer woven covering. I can vouch for that as I have got about 20M of the stuff at home. As there seems to be some sort of interface involved the wire leaving your handset could be anything so I would go with what you measure.

That is certainly a bit bigger than the modern tip which as you say is <4mm (just). I was fortunate that my Goot heater was the same size as the Hakko.
I just measured one of my Hakko tips at an OD of 6.8mm. I wonder if there is enough meat there to get one carefully drilled out in a lathe. It might be worth a try. I suggest in a lathe as you will have to be very careful with drill centring.

I think this is really “you get what you pay for” territory. If you intend to use this iron I would suggest one with a bit of quality about it. Less disappointment that way later on.

Good luck with your search. Regarding Goot/Hakko. The Goot is a very good product (still a current item) but my available real estate on the table is a bit short and the Hakko has a much smaller footprint and I had a voucher to use which offset most of the cost. So I now have a Hakko.
Cheers Bob