Help me repair my solder pot! - Page 1
Forum section: electronics / repair

author: pope
author_rank: Frequent Contributor
timestamp: May 27, 2025, 08:26:40 am
content: Hi all,I have a smallsolder potthat I have hardly used for more than 20-30 hours in total.Recently, the solder pot started malfunctioning. The temperature dropped to the point where it can barely melt the solder inside. At first, I thought the heating element had failed, so I replaced it, but the issue still persists. The heating element measures around 820 ohms, which makes sense for a 65W solder pot running at 230VAC.This pot is really simple in design, the mains go directly to the heating element and that’s about it. So I’m completely puzzled about what could be causing the problem.Do you have any recommendations? I need to get this up and running ASAP, so any hints would be greatly appreciated!thanks!

author: golden_labels
author_rank: Super Contributor
timestamp: May 27, 2025, 09:54:29 am
content: I’m assuming you did check, if it heats up to a reasonable temperature. If not, check that first: attach multimeter’s thermocouple somewhere on the outside, close to where the crucible is mounted on the iron. It’s rated for 300 °C, so let’s say anything above 250 °C measured at that point seems good enough. Also make sure the crucible itself is clean on the inside. A thick layer of grime will limit heat transfer. Not to mention getting dissolved in solder.Their catalogue gives little useful information. Taken from page 40:(1)I’ll make two assumptions:This crucible is simply an attachment to an otherwise standard soldering iron.The soldering iron controls the temperature.Under the above assumptions, the iron is going to measure not crucible’s temperature, but the one of heating element’s. And that leads to two options:The temperature sensing is off. Either the thermocouple or whatever does the temperature control.There crucible lost its good attachment to the iron. The thermal connection is not superior to start with. If the crucible is crooked or loose, it falls to nil. Note that, if there are any screws there, overtightening them may also cause poor connection.(1)Of the 2022 catalogue. The one linked as documentation is invalid. Ersa seems to be attaching their current catalogue to products, regardless of item’s status and presence in the catalog.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 27, 2025, 11:50:46 am
content: Notice that there are two models, OT55 and OT56, for two different working temperatures.The second one is for lead-free solder alloys. Lead-free solder wire has a higher melting point.My guess is you have the OT55 model (for lower temperature), and recently you changed to lead-free solder, and that's why it looks like it doesn't work well any more. Clean the pot and fill it with lead solder wire 40/60, and it will probably work again just as before.

author: pope
author_rank: Frequent Contributor
timestamp: May 28, 2025, 08:27:32 am
content: Thank you very much for the help gents! Much appreciated.It turns out there was a tricky loose connection in the mains cable. One that wasn't visible either to the naked eye or detectable with a DMM. However, when I moved the pot from its place and plugged it into my power meter, the fault was revealed. The power meter would jump from 65ish Watts to random values. At that point, I figures there must be an issue with the mains cable.It'a all sorted now but again, thank you so much indeed for your suggestions!

author: pope
author_rank: Frequent Contributor
timestamp: May 29, 2025, 08:38:46 am
content: Coming back to this, I noticed that the pot isn't as hot as I would like in some situations. The pot is rated at 300°C and I'm using 63/37 lead solder bar.Probably this is a stupid question but can I increase the pot temperature by plugging the pot into my AC power source and drive it with higher Voltage? So, instead of ≈230V from the mains, to drive it with 250-260V...

author: tooki
author_rank: Super Contributor
timestamp: May 29, 2025, 10:15:06 am
content: Quote from: RoGeorge on May 27, 2025, 11:50:46 amNonsense.300C is more than adequate for lead-free (lead-free electronics solders melt at 217-228C, depending on the alloy).The main difference between the two models is the size of the solder bath. The OT56’s bath is nearly 5x the volume, so it needs more power, and presumably they chose a higher temperature because the larger bath will be used for inserting larger items (for example, PCBs with heavy connectors, or thick magnet wires wound into inductors). Or maybe they just repurposed a heating element from an existing model, and the 120W was the closest they had, and happens to be a bit oversized.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 29, 2025, 10:16:28 am
content: Beware that the power increases with the square of the voltage, so the risk is to burn the heating resistance, or to shorten its normal lifetime.If you have a heating resistance of 65W at 230V, at 260V the power will become 65*(260/230)^2 = 83WFor the same heater element, this is almost 30% more power than it was designed, probably too much for long lasting.Another way to increase the temperature may be to reduce the heat losses. Try to "isolate" the heater by using some walls around, to reduce air currents circulation. For example, instead of using that wire stand support, cut a metal can of a diameter just right for the length of the heater, and sit the pot somewhere inside the metal can.