Dead 420 Help please!

Hi Garth,

Address sent via a private message to your good self - click on "Private Messages" on this page header to access your mail.

Peter.

Hi Garth,

Thanks for sending your defunct control board in my direction for disposal. 👿

I thought to put my electrical/electronics so called expertise to the test so as to diagnose the problem(s). A quick check revealed almost a dead short (approx 0.9ohms) between logic 5V and ground.

Fortunately I have a lab power supply on which I can set both output voltage and current limit. So working on the principle that if the supply was set to a couple of volts, and the current to 1amp, whatever was causing the short would get hot when the supply was connected to the board without risking further damage!! And so it did (get hot that is)!!!

The circuitry around the power converter chip is identical to that published in the LM2574N data sheet, and the culprit proved to be a schottky clamping diode which had morphed into a very good 0.5 ohm resistor. Garth had already replace the converter chip, so it was no surprise that when the offending diode was replaced the power converter came to life again with a good solid 5v supply drawing around 150mA.

Of course swapping out SMD components is quite tricky and one needs to be careful not to fry the replacement with enthusiastic soldering, but it worked ok in this case.

Since the design of the converter follows the chip manufacturers recommendations, there are two possible reasons for failure. Firstly it may just be a simple "infant mortality" failure or, secondly, a malfunction of the stepper driver chips which overloaded the 5V logic supply. I wasn't able to check the second possibility without swapping out on my own machine - needless to say that I didn't pursue that one. "If it ain't broke, don't fix it!!"

Peter

Nice work Sir.

Owen S.

Excellent piece of detective work Peter !! I look forward to the first episode of CSI : Stepcraft !!

Thanks for all of your effeorts on behalf of myself and the rest of the Stepcraft community. I know exactly where to come in future for any related electronic stuff. 😉

Cheers,
Garth

Hi guys, i did a mistake on the board and the fuse F4A is broken, i see on some website there is different models of that fuse so i would like to know the spec of that fuse to replace it by myself

thanks
Mirco

The fuse says its specs 🙂 F4A = (F)use 4A(mps) OK?

of course but 30v right?

Jep, Steppi has 30V voltage

thank you Mike