Re: [CAD_CAM_EDM_DRO] MAXNC 10

Hi Chris,

I get 5V from mine! I have a 1K pull-up for the probe line (pin 13). I
need to add another pair for limit switches (not that I'll necessarily
add them to the Sherline), and a E-stop switch (this I think I WILL
add).

I agree, the design is on the "low cost" end. Reminds me of a story in
the late 60's about how Muntz tv's were supposedly designed. Story goes
that "Mad Man Muntz" start with a TV design (perhaps a competitors), and
start removing parts, continuing to remove parts until all that could be
removed without the TV failing were removed.

Alan KM6VV


Christopher Coley wrote:

>
> Has anyone looked at the control box on the MAXNC. Last night I was looking
> for a 5V source in the control box to add a pull-up resistor for Limit and
> Digitizer inputs.
>
> The controller card has a five volt regulator but when measured the output
> was only 2.3V. This is used to power three SN7400 NAND chips that are used
> as buffer inverters to drive the drive transistors, DIRECTLY no limit
> resistor, with a 1K pull-up to VCC (2.4V). This is where the load is that
> is limiting the VCC.
>
> I ended up rewiring and modifying the controller so that it now has the
> SN7400 output go through the resistor to the transistor without the pull-up.
> Now I have a real 5V in the box.
>
> Has anybody else experieanced these issues. I think that MAXNC screwed up
> majorly and thier configuration is bound to fail eventually.
>
> Chris.