first build, faulty heatbed?

I've built a mendel i2, with ramps 1.4 with Marlin firmware
everything runs perfect except for the mk2 heatbed which I've never been able to get going, so I need some help diagnosing why

- bed thermistor is 100k and reads ambient room temp of 17degrees in pronterface
- original atx psu was replaced with this [www.makershop.co.nz] to give enough current
- I burnt out the d8 MOSFET when I first tested as I didn't have the heatsink attached, I'm therefor now testing the bed from d9 (I switched pins in marlin) with the heatsink attached to that MOSFET

- WITHOUT bed connected to d9 - when I set bed temperature ramps LED3 lights up and I get 13V across the d9 and ground
- WITH bed connected to d9 - LED3 does NOT light up and I get NO voltage across d9
note: I have the 2 LEDs and the 1kohm resistor installed on the bed and neither of the LED have ever lit up (both are known to still be working fine)

I'm totally stuck so any help would be really appreciated

Where did you get the heatbed from? And I had similar problems due to power pads on heatbed being connected to copper heat spreader. A photo of the bottom of your board would help

I bought the bed from here [dx.com]
attached are photo's of the bed. (the LEDs are only soldered sticking up like that so I could easily remove them if I had to).
Is it similar to your board? how did you repair it?

Exact one I have. On that bottom picture you need to cut around the pads to seperate it from the copper heat spreader. I cut it with a craft knife. cut on lines like in photo. Use a ruler to get lines straight. Hope this helps

Edited 1 time(s). Last edit at 07/18/2013 04:12AM by tomas02.

wow thank you!
just did what you said and now the LED on the bed is lighting up, i'll clean it up the cuts a bit more before doing a full test though.

I would never in a million years guessed it was that
Thank you so much!!

All thanks should go to Dust.
He helped me with my one.
Hopefully other people that buy from Deal Extreme see this if their boards are the same

tomas02 Wrote:
-------------------------------------------------------
> All thanks should go to Dust.
> He helped me with my one.
> Hopefully other people that buy from Deal Extreme
> see this if their boards are the same

Hopefully other people see this and don't buy from Deal Extreme.