[Scott Kelley]

Is there a schematic available somewhere for the "power dump" circuit ?

[contactirfu]

Is there a schematic available somewhere for the "power dump" circuit ?

yup on the old UHU thread.

[H.O]

You can find it in this post

/Henrik.

[mick22]

Hello,
I have just blown the output on my hp-uhu board,after weeks of being
meticulous, switching the logic first and then the power.

i connected both logic and power to the same toriod and BANG.

when the irf264's and thier drivers have been replaced what else
should i replace.
thanks.
mick.

[kreutz]

Hello,
I have just blown the output on my hp-uhu board,after weeks of being
meticulous, switching the logic first and then the power.

i connected both logic and power to the same toriod and BANG.

when the irf264's and thier drivers have been replaced what else
should i replace.
thanks.
mick.

Just replace the drivers and the Mosfets, check the gate resistors also. Please, post a photo. Paul had a similar issue in the past.

Best regards,

Kreutz.

[mick22]

Irfan,Kreutz,
Thanks for coming back,here are 3 shots of the damaged board.

hope you can see the burnt track around Q4, I hope to repair
this with copper wire hammerd flat.

this is the third time the mosfets have been replaced,and the
board is starting to look iffy!,already the small tracks to Q2 are
replaced with wire.

so i think just one more try before the Z axis on my lathe goes
back to steppers.
thanks for all the help and advice,
rgds mick.

[H.O]

Hi Mick,
I'm sorry to hear you've blown the MOSFETs.... You said you connected both logic and power to the same toriod. What exactly did you mean by that?

I'm not sure exactly what the UHU-chip does during "boot up" but you really should have the logic part powered up before applying the motor power supply.

The other times this happend, was it with the same motor, perhaps you have short in that motor...

/Henrik.

[kreutz]

Irfan,Kreutz,
Thanks for coming back,here are 3 shots of the damaged board.

hope you can see the burnt track around Q4, I hope to repair
this with copper wire hammerd flat.

this is the third time the mosfets have been replaced,and the
board is starting to look iffy!,already the small tracks to Q2 are
replaced with wire.

so i think just one more try before the Z axis on my lathe goes
back to steppers.
thanks for all the help and advice,
rgds mick.

Is this one the only board with that problem?, Do you have other HP_UHU boards?

Maybe there is a defective component on the dead-time circuit (100K resistors) going from pin4 of the Mosfet drivers to GND. check also R22 and R28 (10 ohm) and D4 and D5. Check the PCB traces too.

Best regards,

Kreutz.