M3 trouble

[snowball_rx-7]

went to power up my M3 for the first time when I started to smell acrid smoke.
I quickly pulled the plug. On inspection R9L + and - seem to be the problem. They are discolored. I looked over the board and i dont see any shorts.

 

[Epicurean]

R9 seems to be the output resistors. Are you sure they are rated for as much as they should? Does it happen in all channels or just the left? If the resistors are rated correctly it means there is too much current going through them. I had that problem when I built my PPA and it turned out to be a bad solder joint so I'd double check everything just to make sure and check that all part values are correct.

 

[snowball_rx-7]

Quote:

Originally Posted by Epicurean /img/forum/go_quote.gif R9 seems to be the output resistors. Are you sure they are rated for as much as they should? Does it happen in all channels or just the left? If the resistors are rated correctly it means there is too much current going through them. I had that problem when I built my PPA and it turned out to be a bad solder joint so I'd double check everything just to make sure and check that all part values are correct.

the value is correct, its only on the left channel. Their pretty large resistors, its surprising that none of the smaller ones in series before it are going out.

I'll re-check all the joints tonight.

 

[amb]

Make sure that you didn't mix up the N and P channel MOSFETs (IRFZ24N vs. IRF9Z34N), or reversed the V+/V- connections. Also, did you follow the initial setup instructions and pre-set the BIAS trimpots to their minimum position before powering up?

Btw, there is a dedicated discussion thread about the M³ at headwize.

 

[snowball_rx-7]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Make sure that you didn't mix up the N and P channel MOSFETs (IRFZ24N vs. IRF9Z34N), or reversed the V+/V- connections. Also, did you follow the initial setup instructions and pre-set the BIAS trimpots to their minimum position before powering up? Btw, there is a dedicated discussion thread about the M³ at headwize.

you were right the mosfets were backwards.