Surf pi 1.2 Constant buzzing sound

[Jolly]

Hi
After following the Adrian and genese build for surf 1.2 I got it working and detecting small gold ring at 30 cm, then while adjusting the delay something happened and now it won't detect any thing and a constant buzzing sound is always herd, any help as in to what might have happened would be greatly appreciated, also the Irf 9640 seems to be hot, and the large resistor beside it. Cheers

[chemelec]

Try Replacing your 555 and Check that Q!, 2N3906 Transistor.
Sounds like your MOSFET is Fully Turned ON.

[Jolly]

Thanks chemelec, I will check that out, if that is the case y would the board be working fine for an hour or so then just stop, sorry for the dumb questions I am a new b to this stuff,

[homefire]

Stuff Happens. Crummy Component. Prior Static Damage. While adjusting the Delay you shorted some thing? Adjusted the Delay in a way that subjected Op Amp to more then it was wanting. The Adjustment Pot is Damaged. A number of issues could have taken place. As Stated is sounds like your FET in locked Conducting. Easy enough to check.

[Jolly]

Changed out ne555p, 2n3906 and the 100k trim pot (delay). With no success, any other ideas gents. Cheers

[Jolly]

Also how would one determine if the mofset is staying on.

[jladre]

Try to replace the 5534 and 358.. check also the 470n cap and the solder of your damping resistor.

[Qiaozhi]

Also how would one determine if the mofset is staying on.

Try to replace the 5534 and 358.. check also the 470n cap and the solder of your damping resistor.

Don't just randomly replace components (or even guess which ones might be faulty) in a vain attempt to fix the problem.
Examine the oscillator output with a scope to see if it's stuck on. If it's working correctly, then probe further along in the circuit to isolate the fault.

In case you don't have a scope, either buy one, or find a friend who will lend you one.
Otherwise it's like trying to work with one hand tied behind your back.

[Jolly]

Thanks for the suggestions, turns out it was cd4066, as I had a spare board and components from a failed attempt few years ago, I just swapped out wat I could. Any ways I guess I got lucky, cheers for ur help.

[chemelec]

Glad you got it fixed, but I don't see how the 4066 could cause the MOSFET and that resistor to run Hot.

[homefire]

If your anyway serious about doing builds a scope is more then just vital. You can buy a descent USB based scope cheap. Not a Tektronics but will do anything needed for this kind of stuff.

I have a Hantek 6022BL that includes the Data Analyzer too. Paid $64.00. https://www.banggood.com/Hantek-6022...kaAj1MEALw_wcB