davepick

I'll give it a go... Thanks, Dave.

The original was also shorted (but not in the plug!) I actually pulled the thermocouple off the element without breaking it, and then it measured OK. Anyone know of a high temperature adhesive?!

Thanks Kevin. I've sorted it now, the new element's thermocouple was shorted by the cable-clamp in the DIN plug, slackening that off produced the expected reading of about 10 Ohms cold and around 10mV when heated with a soldering iron. The voltage on the test point only got up to about 2.5V - it should be more than 4V - so I suspected loose connection of the high current heating circuit. It turned out to be a crack in the Schottky rectifier, one leg was a bad joint. Replacing the rectifier fixed that fault and it all works a treat.

I've tried a few more tests (it's cool in the workshop). The thermocouple was short on both elements and produced no volts when heated. I found a similar thermocouple in the junk box and tried that and it worked when touching the element (Voltage appeared on R5 test-point) so both elements are faulty.Oddly when I ripped the thermocouple off the old element it started working! Around 10 Ohms resistance and a few mV output when heated with the soldering iron. Trouble is, there's no way of fixing it back on... New element time.

Yes, of course a thermocouple will have a low resistance... it was the mention of NTC in the service guide that set me on the wrong track.I've seen no Voltage from it but I'll look more carefully with sensitive equipment, as I said there is no voltage on the op-amp output and I've changed it in case it had failed.I wondered if leakage from the element tube to the thermocouple (it measures low) could have blown the op-amp up. I'll try to talk to the LeMaitre man on Tuesday.Thanks for the suggestions.

Hello all.I'm trying to fix this hazer, it goes through the cleaning cycle during which it makes some smoke, then the fan starts and no smoke. The LED flashes one time indicating NTC failure. So I obtained a new element from the customer who had one in stock and fitted that, then I got four flashes (indicating over-temperature) but I guess it could also be caused by thermocouple problems? There is hardly any Voltage on the test point at R5. I just want to know what the thermocouple resistance should be when cold? Both of the ones I have read very low, about 1 Ohm, surely this can't be right? Heating the element up with the soldering iron produced no change in resistance.. suspicious! Physically they look OK no breaks or twists in the fine wires. The elements are quite expensive so I don't want to order another one unnecessarily!Dave.