BMP Mid-bump/Boost Switch Problem

[rocket88]

I built awhile ago a green russian big muff using the V7 layout

The pedal has worked since I built it and it sounds amazing, except there is one problem, the mid-bump/boost switch doesn't seem to do anything. The tone pot just has the normal BMP flat tone sweep.

The only changes I made to the layout was that I used this schematic

for the some cap values changes. And I got my hands on KT3102E transistors and KD521A diodes like the originals were reported to have.

I'm not sure if the changes made increased the amount of bass so much that the switch actually works, but you can't tell or just not at all. The way I connected the switch is I have tone 3 going to the board, and a second wire running from tone 3 to the switch, then the switch is connected to Sw1 on the board. I've checked the board and all the connections and everything is correct. I checked everything with my meter and it seems that everything have continuity, and everything seems to have continuity properly even when engaging the switch. My fluke did say loz when I was checking some parts, not sure if that's good or bad. I also checked the current flowing in and out of the switch, and there doesn't seem to be a change in Voltage when the caps are switched.

I know that I will need to take pictures, but I was hoping someone who has built one of the muffs with the mid-bump/boost switch might have some insight why it might not work until I can take some pictures tomorrow.

[IvIark]

The switch puts the additional caps in parallel with the 3n9 at Q3 collector, and I think it's very obvious switching between modes.  So if it isn't making a difference to your sound then you must have a problem somewhere.  Do you have a capacitance meter?  Is so just measure the capacitance between Tone 3 and Sw1 and see if it changes as you toggle the switch.  If the capacitance isn't changing then you may have a bad contact on the switch or something

[rocket88]

thanks mark. i figured it should be really noticeable. my fluke does have a capacitance setting, and i will check that. where should i check as far as tone 3 and sw1? should i do it from the board connections of tone 3 and sw1 or from the lug of tone 3 to lug on sw1 that goes to the board?

[IvIark]

I doesn't matter, they're all connected by solid copper and so the results should be the same.  Just choose the position that is most convenient.

[rocket88]

awesome. that's what i figured. i checked it and there does seem to be a change in capacitance, but the reading bounces around. i'm not happy with the wire i used so i'm going to redo it all and hopefully that will clear everything up. i'll report back.

[rocket88]

just finished rewiring the pedal, and everything works perfectly. i also replaced the caps on the switch to be safe, and checked that the capacitance change when toggling the switch. i think the caps were bad, and might have had internal damage when i bent them into place when boxing. i didn't realize how much of a difference the switch makes in the mids, best BMP mod. thanks mark, i couldn't have figured it out without you.