Heat bed won't heat
Hi all,
Recently, my printer has stopped heating the heat bed. I took off the little printed piece that covers up the terminals, and I saw that the copper was missing from the voltage line, but was still on the ground line. I used a multimeter on the leads to make sure that it was only the copper and not the wires. However, my multimeter would give me a voltage of around 7 and then drop to 0L. I haven't checked any fuses or the RAMBO board yet, but that's the next step.
Any thoughts?
RE: Heat bed won't heat
Might also be useful to mention... I get sparks off of the terminals on the heatbed sometimes and the LED has been burned out for a while. Has printed until now though. Maybe I shorted a fuse? Thoughts?
RE: Heat bed won't heat
Sparks can possibly indicate a short circuit, but sparks here can also indicate a circuit that is getting broken or interrupted by a small gap. A short circuit would overload the fuse on the board, and you would then have zero voltage on the bed. A broken, or interrupted circuit would cause the bed to fail to heat but it would not blow the fuse. Also, a broken, interrupted or high resistance at the connection point will create a lot of local heating; this can cause copper to oxidize and look black instead of coppery. The place to solve the problem is at the terminals where the wires connect to the board. Gently clean the oxidized copper with a mild abrasive, but don't scrape the copper off the board. Then make sure your connections are tight and secure.
If a digital voltmeter reads "OL" it probably means "Overload" which means the voltage on the terminals of the voltmeter is higher than the voltage range being used. Most voltmeters nowadays auto-range, so the "OL" would show up for a few seconds and then the decimal place would move over one digit and you'd get the actual reading. The MK3 uses 24 volts, so the voltmeter might have been trying to adjust itself. The fact that you saw any voltage at all means the fuse on the board is OK.