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I have a Weller WES51 soldering station with the PES51 pencil. It's about 10 years old however I have kept it very well. I've changed the tip a few days ago and noticed that the tip does not get hot enough to melt the solder. I've turned the temp. dial to max. and tried again and still it would not melt the solder. After the pencil cooled down I took it apart and noticed that the heating element (or at least the part of it that comes in contact with the tip) is heavily corroded, so much that most of it is black. Is this something I can replace or does this mean the entire pencil has to go?

Update - I've spent some time online and it seems that the heating element is something that one can buy online for $40+ which makes it a bad solution as a new pencil is about $50 shipped. Another problem could be the the temp. sensing which might or might not be cheaper to fix but I don't have anyway to measure the tip temp. at this point.

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  • \$\begingroup\$ Weller do a pretty good range of spares. You can probably find part numbers in the manual, which is probably available online. \$\endgroup\$
    – user16324
    Jan 10, 2018 at 22:00
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    \$\begingroup\$ Blackening isn't a sign of failure; it's the way high-temperature alloys oxidize (just like the elements of an electric stove). Temperature sensing might be the issue. Heaters generally work normally, or remain cold, nothing inbetween. \$\endgroup\$
    – Whit3rd
    Jan 11, 2018 at 0:02
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    \$\begingroup\$ Note that even a hot iron may fail to melt solder if the tip surface in contact with the work is oxidized - those oxides can be a surprisingly effective insulator, especially where the joint you are trying to work on has any degree of heatsinking to PCB power planes, non-trivial thickness wire, etc. \$\endgroup\$ Jan 11, 2018 at 2:02
  • \$\begingroup\$ If you remove the oxide, you might also remove the zinc plating that reduces oxidation so it may oxide faster. \$\endgroup\$ Aug 11, 2018 at 3:25

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I haven't seen a failure like this that was due to the base. I have seen failures of the pencil due to the wiring between the base and the pencil. I'd check that first. I've been a working tech since 1981, and I always. preferred Weller equipment.

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It could be the heating element, but it could also be other things like the temperature sensor. I wouldn't try to replace just the heating element in a malfunctioning 10 year old pencil. Just replace the whole pencil. Weller sells them separately.

There is a small chance that the failure is in the base station. If you know someone with a different WES51 (they are quite common), then try to swap pencils and base stations to see where the fault is before spending money. If not, just replace the pencil. That's most likely what failed.

I've got several Weller WES50 and WES51 around here, some over 15 years old. So far nothing on any of them has broken. These things seem to be quite robust. Of course some failures are going to occur somewhere, and you got unlucky. The reason I mention this is that, while it sucks that yours broke, these devices are generally reliable. Replacing the broken part should give you years of service.

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I purchased a WES51 replacement pencil in 2/2023 and also found that the barrel of the pencil would get hot, bit its tip would not reach melting temps even if set to its highest temperature.

As it had a temperature lock, I found a magnet and placed it near the base's lock icon location. The green indicator LED turned red, and the magnet's proximity would make the LED alternate between red or green, solid or blinking patterns.

Bringing the magnet near the base, then removing it, running the base unit through three red-then-green cycles, the unit appears to be working correctly. I don't have its user manual, but I suspect that the two pencils may have had slight differences which needed to be detected or calibrated during this process in order for the internals to properly reset.

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