Help with Marvel Drive

[Smash]

Hello again !

This time I've tried a more complex pedal! (It's just my 5th pedal) and I'm having some issues.
When turned on, the pedal lows the intensity of the signal... meaning, dry signal alright, pedal on low volume...

I've verified the drain voltages from the original as mentioned on the comments:
Q1: 4,0V
Q2: 5,0V
Q5: 5,35V

Mine has the following:
Q1:4,13V
Q2: 5,2V
Q3: 4,66V
Q4: 8,99V
Q5: 5,45V

It's quite close right? Why am I not getting the effect to work?
Maybe my multimeter isn't precise enough? It's quite cheap...

[Smash]

Any ideas are welcome!

[IvIark]

Your voltages look fine, you don't need to get them exact for it to work.  But without the base and emitter voltages there is nothing else to give us a clue what could be wrong

[Frank_NH]

I would suggest making an audio probe:

http://www.diystompboxes.com/pedals/debug.html

If the signal is too low, check the volume pot first, but use your audio probe to see where the signal drops.  Could be a cold solder joint or solder bridge.  Good luck!

[Smash]

Sorry Ivlark! Still learning...

Q1 D-4,53V  S-3,35V  G-0V
Q2 D-5,26V  S-3,74V  G-0V
Q3 D-4,66V  S-0V       G-0,01V
Q4 D-8,99V  S-4,64V  G-3V
Q5 D-5,43V  S-3,63V  G-0,05V

[Smash]

Thanks Frank!

Yeah, I'll build the audio probe... I just have to buy a jack or sacrifice a guitar cord for the purpose!

I've checked for a solder bridge and ran a cutter between the strips. Everything looks in place and the solders seems clean. Maybe I'll just remelt everything just to be sure...

[Smash]

Do you guys see anything suspicious?

I can't tell...

[Frank_NH]

The voltages are probably OK.  I'm assuming you have turned up the volume, treble, and normal controls to max and it is still less than unity gain.  Use your audio probe to see where the signal drops.  Start from the output and work your way backwards.  This pedal should put out lots of volume.

[pnadora]

Hey smash,

I see this post is a bit old, but I have the same problem after building the pedal last week. The volume is pretty low and the gain is also nowhere near the gain levels of the original. With everything at max its like a light crunch. Did you solve the problem on your pedal in the end? Any help is apprechiated!

All the best
pnadora

[Travis]

Assuming you've already audio probed this and are still stumped..

What JFETs are you using? Where did you buy them? Most of the popular JFETs on the market right now are fake or out of spec unless you pay up or use the SMD versions

[ibanez48]

Travis how can u test a jfet. I bought 100 j201 I haven't had any problems with them yet. Are they a way u can check them thanks.

[Muadzin]

I thought I had good JFET's too, as I got volume and the pedal I used them was advertised as a low gain pedal. Then I tried to build a Pinnacle and was underwhelmed. Then I learned ALL my J201 JFET's were fake. I ONLY use SMD JFET's these days.

[Travis]

You could use this to see if they are out of spec

http://tagboardeffects.blogspot.com/2012/07/greatly-improved-jfet-matcher.html?m=1

But if you got them cheap from China or something those are pretty much all fake/out of spec