Your CTC may be type K but my CTC is type T. I have been working with thermocouples for the last 50 years, and have made thousands of them for manufacturing facilities temperature processes.
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3 months later
If your thermocouple problem has not yet been resolved, keep in mind that in most fitted thermocouples you’ll find on the webstores, the thermocouple itself is NOT insulated from the press-fitted ring. That’s a no-go for most CTC builds as you could fry the thermocouple converter ICs on the motherboard. I replaced mine and (luckily) discovered this before installing them. I insulated the coupling with Kapton tape before refitting the ring over it…
4 months later
Hi,
Can you give me more detail on what you mean? As my old thermocouples look the same as my new yet i have indeed fried the boards chip. New board on the way.
Well, the CTC & Makerbot web sites say that the TC’c are type K (color code on wires Red & Yellow) I found that my CTC printer the wires are type T (Color code on wires Red & Blue). On type T TC’s one of the wires is copper and the other is silver color. Remember that TC’s are DC millivolts so polarity is important.
Hi. Sorry for the late response, I’ve been ill…
The main cause for burnt out MAX6675 is that the fixed “+24V” wire entering one of the heater cartridges is sometimes exposed and can be in contact with the heater block. If this happens and your thermocouple is not electrically insulated from the chassis, you’ll be sending 24V down the throat of the 5V MAX6675 input lines, frying it instantly (nearly any silicon junction dies by shorting itself, but if the current is sufficiently high, it can evaporate). So, if the short between the +24V and the heater chassis is maintained, the MAX6675 silicon die could be evaporated. In this case, the +24V could potentially propagate to any other IC on the board, including the CPUs.
That’s the reason why on my boards, I do two modifications :
- Connect a chassis drain wire between the heater block assembly and the power supply ground line (earth).
- Insulate both thermocouples with Kapton tape. To do this, I carefully open the FastOn eyelets, insulate the thermocouple with two to four loops of Kapton tape, then reseal the eyelet. This introduces a small offset in the head temperatures reading, but it never has had any adverse effects on my prints.
I hope these explanations are meaningful for you. In any case, contact me if you need more information or a clarification.