SOLVED Pro-10 green side no gain low output

[Grazza]

Hi all,

Just finished those pro-10, blue side works great, green side however has really low output and no gain really to speak of. There is some sound coming though but not much. When green and blue on together it drops everything down to green output. I'm baffled! I noticed someone else has similar problem but not solved yet either. Any assistance would be greatly appreciated. Pic attached.

 

[Grazza]

I just tested the little j201 that is on the little circuit board and my TC1 tester says that the source and the drain are opposite to what is labelled on the circuit board the SMD jfet is on, could this be correct?

 

[music6000]

I was just about to ask about the SMD used, Interfet brand have them as opposite on thru hole version???
Maybe someone else can chime in as I only use NOS J201's thru hole.

 

[Grazza]

I've just soldered longer legs onto the adapter PCB and I'll bend them around. Gate is the same. I don't know if you remember, but you were helping me with a m800 PCB using these transistors and adapter boards I never got working, I haven't gone back to it yet, but if this solves this problem then that will be the same issue with the m800

 

[Grazza]

Nope, I swapped the drain and source like my tester said and I actually made 0 difference, still getting sound through but no gain, is it the 4558s maybe?

 

[music6000]

They look like genuine 4558's, try TL072's in there.

 

[Grazza]

Will do, the rest of the batch I bought have worked, could be a long shot

 

[music6000]

Failing that, here is the Resistor Calculator, click on Bands for 5 colours:

Resistor Calculator

Resistor Calculator is an App developed by CherryJourney to help the user find the value of a resistor.

resistor.cherryjourney.pt

 

[Grazza]

Same with the TL072s, I have sound but there is a big drop in gain when engaged, it turns a driven sound clean. I'll have a look at that resistor calculator, you think I have just put in wrong value resistor or cap?

 

[Grazza]

Please bear with me, but I have begun to check all of the component values. Not only am I checking the bands but I have been putting a multimeter accross the resistors too. I have noticed that some resistors vary wildly from what is on the band. Eg the 1m down bottom left, can tell you its number because there are no build docs, but it reads 32K instead of 1meg. Am I being stupid in putting a DMM on them as they wont read what they say they should because they are now in the circuit? I dont test every individual component because I didnt think I needed to, but if this is actually whats happening I need to through a good amount of my components in the bin. 99% of it bought from Tayda, I thought they would be really good.

 

[Grazza]

The resistors circled in red measured no where near what the coloured bands says on them, turns out my 15k resistors are rubbish. Would this affect the circuit to the extent I am seeing. Also only really checked what I thought was the green side.

 

[music6000]

You can't rely on measuring Resistors in the finished build!
I have never had a metal film resistor measure outside its tolerances & I have built close to 300 pedals.
Have you got a measurement of the 15K resistors out of the circuit?

 

[Grazza]

Yep, I was wrong, they measure good, man I am really struggling with this one. Was looking forward to it more than almost any other pedal ive built. Dont know whats wrong with me, got a trembling lune I just built before this one I have to trouble shoot too. I thought I nailed it as well, but it does nothing

 

[music6000]

What voltage are you getting on the Q1 Drain of J201 & Collector of Q2 - 2N3904?

 

[Grazza]

8.43V on the J201, presuming I have it in right being one of the SMD Fets.
8.43V again on pin 3 of the 2n3904

 

[szukalski]

 

[Grazza]

whats that about the school canoe? I'd like to, but I don't have an audio probe, or really know what to do with one. Is it something I buy or something I make?

 

[szukalski]

I am sure you can buy them, but they're only a few components:

Misc > Audio Probe : DIY Fever – Building my own guitars, amps and pedals

[DIY Fever] Audio Probe - very simple contraption that helps with debugging audio circuits

diy-fever.com

 

[Grazza]

I'll check it out

 

[Grazza]

That looks pretty simple. So just follow the schematic (of which there isnt one on this build) and follow the signal till it stops and that is the problem area?