Promethium woes once I get to the buffer stage.

[Yroc006]

I have a great signal all the way through until I hit the Q4 2N3904. Then is just fizzles out into a crackly mess. I'm not entirely sure what would be causing the issue unless it's voltages (maybe)? I'm getting 4.3v at the (2) Base (which appears to be in line with the Vrefs), 5.38v at the (1) Emitter and 9.23v at the (3) Collector (which i'm assuming is correct since it's getting power straight to it from the VCC in the schematic). The signal is totally fine though C21 and R21, I can hear it hitting the Base of Q4 at a good volume, but poops at the Emitter. Any ideas? I could potentially just go out straight from the volume pot and be done with it as I've read the buffer stage isn't really needed but I'd rather try to figure this out first. Any thoughts would be appreciated.

 

[fig]

I think it's going to rain all day...

OH! Thoughts about the problem...do you have another 3904? have you double-checked those 3 resistor values, and cap value down the line?

 

[Yroc006]

i've tried a handful of 3904s and get the same result. Went through and checked resistor stripes and capacitor codes and everything appears to be correct. I also measure every component before soldering to slow myself down and double check as I'm building. That's why this is vexing / frustrating.

 

[Yroc006]

Actually just checked those voltages against an Aion version and the voltages are pretty close, which makes this a little more confusing. The Aion is a volt lower on the base and emitter, but i'm not sure if that would be enough of a difference to cause this issue. Yes, I'll build the same pedal from two different places. I like to build things, I know I have a problem.

 

[fig]

Bad socket?

 

[Yroc006]

Maybe? I though a 2.7m in 31 which brought down the base voltage to 3.6, the the emitter is still high. To make matters worse, I was actually building 2 of these at the same time but didn’t have the pots in yet. So though those in and the second one fired right up with the voltages being in-line with the Aion. So now I get to slowly go through the first one again and see why the voltages are off. I’ll start with replacing that socket and move backwards from there, but at least I have the second board as a reference.

 

[giovanni]

The voltages above seem normal to me, a plain old emitter follower biased at half Vcc. You wouldn’t measure those if you had a bad socket.

 

[fig]

The voltages above seem normal to me, a plain old emitter follower biased at half Vcc. You wouldn’t measure those if you had a bad socket.

Doh!

If the circuit can't continue past the emitter pad due to a faulty solder...the voltages would reflect an open circuit (OL on DMM)?

Edit:

 

[Yroc006]

I’m going to do some measuring though both boards today and see if I can find the issue.

 

[Yroc006]

Measured Q1-3 and everything was in line. So i went went scorched earth and pulled out R31-35 and just replaced everything and it fixed the issue. Honestly not sure what was going on. I didn't have any solder bridges (that I could see anyways), but it's working now. @fig thanks for the suggestions, appreciate you reading though my problem solving thought process. @giovanni I appreciate your input as well. glad we could all take this journey together! xoxo

I think I fried the FV-1 on my guitar doubler, so you'll probably be hearing from me again soon!

 

[giovanni]

good to hear!