[Noisebridge-discuss] Laser Cutter Repair Work

Henner Zeller h.zeller at acm.org
Tue Oct 27 06:03:36 UTC 2015


Hi Zach,

Thanks for your work. I was discussing off-line with other NB's  your
findings in the space, but when you mentioned it today noticed that
nobody replied to this mail yet.

On 17 October 2015 at 12:36, Zach R <organicunity at hotmail.com> wrote:
> Hey all,
>   So me and some NB-ers took a closer look at the Lasercutter on Thursday
> night.  I took some pics that I'm too lazy / carpal tunnelled to upload
> right now but here's the gist of it:
>
> 1) someone has definitely tampered with the boards inside
> 2) the main I/O board is there but there is what seems to be a parallel port
> to USB adapter board missing

I had a brief look inside and the interface looks like a parallel,
though it is not entirely clear if this is
standard centronics/sub-d 25 pinout (as this is a 0.1" pin header).
FWIW, I have a usb/sub-d 25 printer converter
lying around somwhere (if this is what it is).

I have a similar laser cutter at home, but it has a direct USB
connector, so a completely different control
board - so not of much help here to compare. I guess we have to
somewhat reverse engineer to figure
out if this is indeed a parallel input. Did you take pictures of the
top and bottom of the board to aid reverse engineering ?

The problem with the control board that I have is, that it has some
chips on it which even some internet search does not yield any result.
Main problem is, that we can't even hook it on to see what signals
there _should_ be.

I think the general category of this laser cutter is 'K40' - some
generic chinese brand that roughly looks like the one we have (we have
a re-branded one in the space).
The control board probably has changed a lot between the generations
and cannot be compared.

> 3) The main power PCB needs some major work.  Someone removed the heatsink
> mount on the main output transistors and another was not properly insulated.
> I fixed these issues but I think its possible (and worth replacing) the 4
> power transistors in there (it would cost around $15 in parts).

+1 (we might even have some replacements at Noisebridge - I certainly
have seen some beefy transistors, but not all specs are entered yet in
http://pegasus.noise:3000/search

> 4) Someone replaced the main 6A 250v fuse for the power board with a HACKED
> DC 30A(!) fuse.

Yikes!

>  Lols.  I put a 4A one in there now since NB had no 6A ones
> on-hand

> 5) I don't think the system turns on right now.  When you turn the key over
> the LED lights and fans come on, but these are from separate power supplies
> (I believe the fan runs off AC).  So the main board is not working at this
> point I think, since the +24v and +5v output LEDs do not light up and I
> measured nothing there (+2v give or take).  The I/O board could send a
> startup signal to it, but I kinda doubt it.

Ok, that is a good start. A power supply should be easy to get going
in isolation.

If the control board is too complicated, I am happy to donate a
Beaglebone Black/Bumps combination running BeagleG (which would allow
as well a simple network connection for the device, including local
processing power).
I can hack the software to output a PWM signal proportional to the
moving speed if someone else can try to get the laser tube running
again with the remaining (and possibly to be restored) power supply
unit.

That way, we can ditch the old controller board, but it still leaves
some diagnostic work in getting the supply up and running again and
some reverse engineering on the board to figure out how the tube is
powered and PWMed.

-h

>. However, this requires that we get to get the laser tube and the PWM running.
> I could go more in-depth with the repair later on.  A Service Manual would
> REALLY help with this.  If anyone can help source that / send me links to
> any schematics and info on this thing that would go a long way.
>
> -Zach
>
>
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