I have a tone control, not a boost!

[graylensman]

I built the beginner project, and it works...sort of. I have bypass, I have signal when switched on. But I don't have boost! It's acting more like a tone control: turn the knob clockwise and the treble in the signal increases. I looked over my work, and I can't see any errors, but clearly there's something I missed.

Can anyone point me in the proper direction to troubleshoot this? Many thanks!

[Gus]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[graylensman]

thanks! I'll go through the steps in the next few days and report back. 

[Thecomedian]

Did you have an original schematic you worked from?

can you post that schematic?

can you post a current schematic of it? Trace the connections and draw out the physical connections on a sheet of paper. You might see the problem immediately, but you can also post it and see if we can see the problem.

[graylensman]

Thanks for the replies. I'm planning to get to this this week. But of course, I said that last week...

[graylensman]

Okay - reporting the info. I'm not sure some of it makes sense....

The schematic is the Beginner Booster Project from right here at DIYStompboxes. It's supposed to boost volume, but my circuit is acting as a tone control.


There are no modifications to the circuit. There are no parts substitutions. I used a fresh battery, which tested at 8.00. Voltage at circuit board positive end: 7.97. Voltage at circuit board negative end: 0.00.

This circuit uses only one transistor. This is where it gets weird. The expected values (according to the schematic) for Q1: C=6.84, B = 2.82, E=2.19. The values I measured are: C=7.50, B=.943, E=.435.
Additionally, the schematic shows a value where four resistors meet = 2.83. I measured 1.326.

As far as I can tell, my connections are good, all components are connected as indicated in the schematic (and through the tutorial). The bypass functions properly, and the LED lights up like it should.

Obviously, looking for some help.  THANKS AGAIN!

[duck_arse]

measure the voltage at the point marked "2.83", and then check your resistor values and soldering in that area to see why this voltage is wrong.

does the voltage at your emitter change when you turn the boost pot? if it does, you have the pot wiring wrong.

good luck, and feel free to show us photos of your work, it often helps.