Surf PI No Sound and Hot FET

[jvanostrand]

I just built a Silverdog Surf PI and when I power it up there is no sound and when I connect the coil the FET slowly gets very hot.

I put a DIY oscilloscope on the coil connections and I see a square 54ns pulse, 46% duty cycle. The voltages seem to be fine. The coil is 24awg speaker wire, 6.9" ID and 29 turns, 1.7 ohms a little more with leads on it.

I'm guessing the PCB is okay but the coil is drawing too much power? To test a higher ohm I connected the rest of the speaker wire (on spool) in series with the coil for about 2.5 ohms and I still had a hot FET.

https://drive.google.com/open?id=0B-...0NJcDNaZDlNQ2M

[kt315]

8 kHz? it seems you do a VLF not PI...

[FatBob]

well 54us is OK for pulse width but .1ms for Rep should be 1ms are you sure the 100k (R1) on the 555 is correct?

[kt315]

8,5 khz is abnormal freq for the md. you have to have 800 Hz.

[jvanostrand]

Thanks FatBob,

You were correct. The kit shipped 1K resistors labelled as 100K. That's the third mistake on this. I won't know if that's the only problem until tomorrow, I need 100K resistors.