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Old 31st Jul 2021, 5:44 pm   #1
Techman
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Default Unknown soldering iron question

These two soldering irons came in a box of electrical bits and pieces from someone I know who gets given stuff and then passes on to me what he doesn't want and I was wondering what base they would have originally gone with. The chap I got them from thought they were 24 volt and I note that one of them has a label marked 'US', so would seem to indicate it to be faulty. They are fitted with 5 pin 'mic' style socket plugs and the one marked as 'US' has obviously had its wiring altered onto different pins, the other one looks to be original.

On the 'originally' wired one I'm getting around 12 ohms between pins 1 & 2 which is green and red. I'm getting around 2 ohms between pins 4 & 5 which is yellow and blue. On the probably faulty one I'm getting 2 ohms only between yellow and blue and nothing between any of the others.

Does anyone know anything about these particular irons and whether I can hook them up to make any sort of use out of at least one of them, keeping the probably faulty one for handle parts and a spare bit?
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Old 31st Jul 2021, 5:54 pm   #2
duncanlowe
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Default Re: Unknown soldering iron question

My thoughts were Maplin. https://www.maplin.co.uk/maplin-a40k...-5055189030992
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Old 31st Jul 2021, 6:08 pm   #3
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Default Re: Unknown soldering iron question

Well spotted! Thanks.

My guess is that the 12 ohm connection is the element and the 2 ohm connection is to a temperature sensor of some sort.
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Old 31st Jul 2021, 6:26 pm   #4
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Default Re: Unknown soldering iron question

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Originally Posted by Techman View Post
Well spotted! Thanks.

My guess is that the 12 ohm connection is the element and the 2 ohm connection is to a temperature sensor of some sort.
My thought would have been the other way round. 2 ohms for a sensor means that any connection resistance would have a significant effect on the sensing. Whereas 2 ohms would likely increase quite fast to something reasonable for a heater (a bit like lightbulb filaments are very low resistance when cold).
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Old 31st Jul 2021, 6:43 pm   #5
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Default Re: Unknown soldering iron question

Get another iron to heat it up and see how the two resistances change. The one with the biggest change will be the sensor.
Be very cautious about applying 24v. I have one of the Chinese two station jobs, and a failure meant no control, and the barrel was glowing in double quick time. Followed by burn out if you don't switch off quickly.
Les.
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Old 31st Jul 2021, 8:19 pm   #6
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Default Re: Unknown soldering iron question

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Originally Posted by duncanlowe View Post
My thought would have been the other way round. 2 ohms for a sensor means that any connection resistance would have a significant effect on the sensing. Whereas 2 ohms would likely increase quite fast to something reasonable for a heater (a bit like lightbulb filaments are very low resistance when cold).
2 Ohms would be OK for a thermocouple, and as that's a voltage source working into a high Z load, then cable resistance isn't important.

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Old 1st Aug 2021, 12:00 pm   #7
Techman
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Default Re: Unknown soldering iron question

Thanks everyone for the thoughts and suggestions. I gently heated it in a gas flame and the 2 ohm resistance started to increase on a DMM, but I quickly noticed a '-' indication on the scale, so immediately changed to a voltage range and there was in fact an increasing voltage that went from 3mV to over 10mV during the test, so yes, it is a thermocouple that must feed back this small temperature dependent control voltage to the base that it would have been fitted to. The other 12 ohm connection did indicate a slight increase as you might expect a heating element to do when warmed up.
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Old 1st Aug 2021, 12:29 pm   #8
peterpiper
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Default Re: Unknown soldering iron question

Hi, Its a Hakko T12 or a clone of. It needs a controller (check the net) and a 19v power supply i.e. Laptop. Great iron I've used it for 4 years

Peter
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Old 1st Aug 2021, 12:37 pm   #9
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Default Re: Unknown soldering iron question

Hi, thanks for that information, I was wondering if anyone would know the make, I'll check it out.
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Old 3rd Aug 2021, 6:57 am   #10
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Default Re: Unknown soldering iron question

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Originally Posted by peterpiper View Post
Hi, Its a Hakko T12 or a clone of. It needs a controller (check the net) and a 19v power supply i.e. Laptop. Great iron I've used it for 4 years

Peter
Agreed, cheap controller clones are available from e-bay, ali etc. Just make sure you get the right one, there is also a Hakko clone iron and controller that uses a thermistor not a thermocouple and the seller's tend to use the same number for both. I have bought several that turned out to be the opposite of what was listed.

Peter
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Old 3rd Aug 2021, 7:25 am   #11
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Default Re: Unknown soldering iron question

Yes it's a Hakko clone. Also sold by RS as the RS Pro.

Beware: they can have totally different wiring of the sensor/element connections in the plug.

Also the sensor resistance is different for different versions, as I found out when trying to replace one.
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