Incorrect connection of the TC and heater

[richard-sim]

Hey, I was looking over your schematic and it looks like you're powering the heater through the TC as they're connected in series in the cartridge with the 3 wires being either end and the common point between them. Going by the Bottom schematic, C245_JUNC is the common connection between the heater and the TC, so the heater should be powered by J3.1 (V+/heater) and J3.3 (C245_JUNC/common), and the TC sensed between J3.4 (TC) and J3.3 (C245_JUNC/common).

[dreamcat4]

This eevBlog Forium thread discussion goes into a lot of details about the C245 Tip. And is the best source of information I have found on the subject. It's probably worth the time to read the comments over there.

[richard-sim]

There's an even better EEVblog forum post where someone has reverse engineered the entire circuit of a JBC CD-2BC: https://www.eevblog.com/forum/testgear/jbc-soldering-station-cd-2bc-complete-schematic-analysis/

To correlate the terminology from the schematic and the image I've included below:

• COM = pin 2 of the connector = connection at the base of the cartridge = JUNC in the Otter Iron PRO
• LOAD = pin 5 of the connector = connection in the middle of the cartridge = HEAT in the Otter Iron PRO
• TC = pin 1 of the connector = connection to the body/tip of the cartridge = GND in the Otter Iron PRO

If you look at that the top of page 2 of the schematic from that thread, it's clear that C245 (and C210 for that matter - but they're a different beast in other ways) cartridges will have their heaters powered through the COM and LOAD pins only - never the TC.