Solder Station Replacement Iron Glowed Red Hot and Burned Out

Thread Starter


Joined Jan 9, 2019
Hi all,

My question: What could cause a soldering station replacement iron to glow red hot and burn out?

More detail:

I used to work for Maplin Electronics and am an electronics hobbyist.

I purchased a solder station (Precision Gold A55KJ)

Precision gold was a Maplin phantom brand and the OEM of this station is Atten. The model is 938D (spot the difference!)

I snapped the handle of the original after 5 years of reliable daily use.

I opened it up and discovered that it is the 2 wire version (same as the 938D). It "regulates" temperature based on heating element resistance. Alas I didn't know that when I bought it! There is a 4 wire (980D) which includes a thermocouple.

The iron has a 5 pin connector.
Pins 1 and 2 shorted at the plug and connected to one wire in the flex for one wire of the heating element.
Pin 3 connects to the iron's body (ESD ground)
Pins 4 and 5 shorted at the plug and connected to the final wire in the flex for the other wire of the heating element.

I purchased a new iron specified for the Atten 938D and it turned up today.

As I was aware that there are two versions of this iron, I decided to measure continuity between 1 & 2 and 4 & 5. Short as expected. Pin 3 shorted to the iron body as expected and 10Ω between 1 & 5 (element resistance) as per both manuals.

I set the station to 315°C and the 3 "applying power" bars lit up on the screen as expected. These usually drop to 2 and then 1 as the iron reaches temperature.

This time they didn't and the tip began glowing bright red. I quickly killed the power and left it to cool.

I opened up the iron, confirming that the PCB is identical to the original. I measured the resistance of the element and now it's open circuit and obviously does not heat.

I measured the output from pins 1 and 5 on the station and I get 32VAC (not far off the 28V specified) however it no longer displays the "power" bars and the temperature display reads 000 so it must be detecting the open circuit / lack of current draw.

My main question is: Do you sometimes get faulty elements that short when new and burn out or is it more likely that the controller isn't reading the coil resistance properly and is just constantly applying power?

If so, what's the best diagnostic method? I don't want to return the iron as faulty, get a replacement and have the same issue.

On a related note, any recommendations on decent solder stations if this one turns out to be a Norwegian Blue? Preferably something under £100, a hot air rework attachment would be a nice to have too.

Thanks in advance