Soldering Iron fuse blow predicament.

Thread Starter

SeanV123

Joined Nov 12, 2020
68
Hello, I have this soldering iron. It used to work perfect for me but now every time I turn it on the fuse in the station blows. I bought repleacment fuses as per the manufacturers specifications and they still blow when I turn it on. But here's the weird part. When I turn on the station woth the iron unplugged it stays on. However when I plug the iron into the station the fuse blows straight away. Is there any reason for this? It worked perfectly before and this is only a recent problem. I took the iron apart and everything seems okay. I really want my iron to work so I can stay occupied over the Christmas as my country is back in lockdown. Thank you!
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Thread Starter

SeanV123

Joined Nov 12, 2020
68
Thank you for your reply. I am quite new to this so which wires will I check? I took the iron apart and all the wires look good and well connected
Apologies. Wrong reply. How would check the resistance of the heating element. I have a multimeter. What would I be looking for, as in how do i know if the heating element is the problem or not ?
 

Thread Starter

SeanV123

Joined Nov 12, 2020
68
One other thing. I live in Ireland and the mains voltage is 230V. The fuse I'm using (according to the manufacturers specifications says 315ma 250V). Would that cause a problem? As I said, I used this iron before without problem so I can't see why it would .
 

dl324

Joined Mar 30, 2015
12,871
Thank you for your reply. I am quite new to this so which wires will I check? I took the iron apart and all the wires look good and well connected
There are 3 wires in the iron cable. When you look at the pins in the connector, the one on the right should be connected to the metal sleeve. The other two are the heating element.

You should measure an open circuit from either terminal of the heater to the sleeve. The heating element should be around 12.5 ohms. Make sure you subtract lead resistance from your measurements.

If the element is good, the transformer secondary might have shorted. Caused by an over current that the fuse couldn't protect from.

EDIT: The latter is unlikely because the fuse doesn't blow if the iron is disconnected. When my element failed, it failed open.
 

MrChips

Joined Oct 2, 2009
23,508
If your fuse blows then it is likely that there is something wrong such as a short in the wiring or a bad heating element.

Disconnect the unit from the wall AC outlet.
With the power switch in the ON position, measure the resistance between the two power prongs on the AC power plug (with a good fuse installed.)

With a flat blade screwdriver, turn the AC voltage selector switch back and forth a few times.
Measure the resistance at the AC plug with the selector at 110VAC.
Measure the resistance again with the selector at 220VAC.
Leave the selector set to 220VAC.

Do not attempt to turn the unit on until we see your measured readings.
 

Thread Starter

SeanV123

Joined Nov 12, 2020
68
There are 3 wires in the iron cable. When you look at the pins in the connector, the one on the right should be connected to the metal sleeve. The other two are the heating element.

You should measure an open circuit from either terminal of the heater to the sleeve. The heating element should be around 12.5 ohms. Make sure you subtract lead resistance from your measurements.

If the element is good, the transformer secondary might have shorted. Caused by an over current that the fuse couldn't protect from.

EDIT: The latter is unlikely because the fuse doesn't blow if the iron is disconnected. When my element failed, it failed open.
Okay thank you.
 

Thread Starter

SeanV123

Joined Nov 12, 2020
68
Only if it's shorting the heating element or element to case. The resistance checks I told you to make will tell you if there's a short.
Okay Thank you. I will do them soon. I will keep you guys updated on my progress. I have never found a more helpful and modest community than the electronics community. I am grateful to be pursuing a career in electronics while also becoming a electronics enthusiasts!
 

Thread Starter

SeanV123

Joined Nov 12, 2020
68
That could be the location of a short circuit if the splice was not well done.
Check the resistances as described above.
Yes I was also thinking that. I asked my father (well accomplished tradesman) for his opinion and he told me exactly what you guys are saying. Great minds think alike!
 
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