Angry Andy +, constant buzzing on boost side when switch on

vambriz

New member
Hi all,

As the title mentions, I have a constant buzzing/humming on the boost side of the pedal when I hit the switch on. I used an audio probe to detect where in the circuit the buzzing begins, and it happens on the "D" leg of the BS170 mosfet. I replaced it with an NTE490, but I still get a buzzing. Before replacing the BS170, the LED for the switch was working and now it does not. The Buzzing continues even if I strum the strings. What should my next steps be? I have a multimeter, but just not sure how to apply it for this application or what measurements I should be getting.

As a side note, this was my first build ever from about a year ago and I've come back to fix it. The overdrive section works flawlessly. I have not encountered any issues with it as far as I can tell. However, I definitely made some mistake wiring up stuff in reverse so there might be some damage that I am not aware of. Any tips on how to troubleshoot further is much appreciated.

Thanks for reading. Link to Schematic
 
How loud is the buzzing? I had a low hum on mine, and then I made sure that the stomp switch was properly grounded to the case (it hadn't been) and the noise stopped. Also, be aware that the way this boost is designed, you will get crackling if you adjust the boost knob at all with it on. That is just the design of it and is normal.
 
How loud is the buzzing? I had a low hum on mine, and then I made sure that the stomp switch was properly grounded to the case (it hadn't been) and the noise stopped. Also, be aware that the way this boost is designed, you will get crackling if you adjust the boost knob at all with it on. That is just the design of it and is normal.
It's pretty loud. If I strum the guitar, I do not get any sound out the amp, just the constant buzzing. I'll double check the connections. I have already had 2 break at the switch breakout board. This was my first pedal and I did not do the solder very good.
 
So I finally got a multimeter, I measured all the resistors for the boost circuit. I was getting 350 Kohms for R27, R29, and R30. I compared with the stripes and color combination of my other 1 Mohm and they're exactly the same colors. Why would I have a different resistance? I also had a lot of flux left over that I cleaned today with a toothbrush and isopropyl alcohol.
 
reading high value resistances can be tricky because the input impedance of the meter is in parallel with the resistor. Cheaper meters tend to have a lower input impedance - often around 1MOhm. Parallel that with a 1M resistor and you read 500k. If you are measuring in circuit then you may be getting some impact from other components as well.
 
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