I have just got around to looking at the open circuit heater that came with the spares donor unit. I am please to say that the element is nowhere hear as badly damaged as some I have seen in hot air stations. I had one faulty unit come to me and the 'rats nest' of an element was a mass of melted wire along its entire length. Thankfully that element cost only $10 to replace. The JT6040 element is not available separately from the barrel and is a smaller diameter than used in most hot air stations. Including taxes, the JT6040 element 'module' costs around £250 ! I would like a spare element as insurance so there is some incentive to repair the faulty element, if feasible.
I consider that I got lucky with the failure of the element. it could have been so much worse. I extracted the element from the hot air barrel and its associated thick mica insulator tube. It is the same 'rats nest' design found in many hot air stations. it is an element design that has always puzzled me. It has no real former and looks so disorganised.
The heating element appears to have been the victim of abuse or a fall. The ceramic is broken and the end few turns of element have burnt out. Thankfully the break in the element is at the very end and limited to few turns so I can connect the remaining element to the power terminating node at the tip. I will have to carefully wrap the element wire around the thicker metal termination node and weld it in place using a carbon rod welder
The loss of a few turns of the element is unlikely to cause any issues in this use case. I will repair the broken ceramic 'spine' using a combination of high temperature stove glass adhesive and high temperature ceramic cement. It should do the job and I have used it previously to repair a mineral insulated heating element that had shorted to its metal casing.
Pictures of the poorly element attached. The repair will have to wait until I have more time but at least I now know it appears to be a viable repair. I need to make a simple carbon rod welder to weld the element but that can be done with nothing more complex than a carbon (graphite), some clamps, thick wire and a car battery
This is small scale carbon rod welding.
In case anyone is wondering why there appear to be two thermocouples in the heating element.... there are. The JT6040 monitors the temperature entering the heater and leaving it. Most other hot air stations monitor only the temperature of the air leaving the heating element and wand/handpiece barrel. The JBC monitors the Delta T across the heating element as part of its closed loop temperature control system.
Fraser
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