Chunk Chunk Low Volume

[strat56]

Hello again,

I'm testing my Chunk Chunk and it has extremely low volume when engaged.  I tried tracing the audio path with a tester that I made but it's very confusing for me.  It seems like the red lines supersede the blue lines so when a red trace and a blue trace are in the same place on the board, all I can see in the picture is the red one. Is there some trick to reading and understanding this or do you just have to do it enough to get good at it?

As an electronics newb at the age of 60 I have a couple questions. 

Can I test for the value of resistors and pots while they're soldered to the board?  Seems like it works sometimes but others no.  Same question for caps I guess.

Here's what my tracing has given me so far.  Signal is low at Q4, louder at Q1, louder stiil at Q2 and loudest at Q3.  Does this seem right?  All are biased close to 4.5V. 

The output from the volume control is very weak.  The gain control however is making the sound distorted and I can hear the tone controls changing the sound when I turn them.

I see it looks like sometimes caps and resistors will just be connected to ground on one side. For caps I think this is to bleed off certain frequencies but I could be wrong.  What does a resistor do in this case bleed off excess voltage?

Thanks,
Jack

[strat56]

Can anyone help me here?

[jimilee]

Can anyone help me here?

Up close clear well lit pictures would be most helpful. The redlines are power, the blue lines are audio, thick lines are on top of the board, thin lines on bottom.

[strat56]

Pics here, let me know if you need anything else.

[strat56]

So I was looking at these pictures and realized I have Q4 in backwards!!!  I must've looked at that 50 times already.

[jimilee]

Sometimes, I take pictures of my builds, it helps. Does it work?


Sent from my iPhone using Tapatalk

[strat56]

It does I think, I played it a little thru a little amp I have on my workbench before I boxed it up but when I was boxing it up the ground wire broke off at the board.  I'll fix it tomorrow and try it thru a real amp.

[jimilee]

Woohoo!!!


Sent from my iPhone using Tapatalk

[somnif]

Your battery wires are also swapped, Red on (-), black on (+). (I realize you probably know this but it bugged me. Backwards!)

[strat56]

Your battery wires are also swapped, Red on (-), black on (+). (I realize you probably know this but it bugged me. Backwards!)

I didn't see that, thank you.

[strat56]

Your battery wires are also swapped, Red on (-), black on (+). (I realize you probably know this but it bugged me. Backwards!)

They weren't, there is a - right in front of the black wire and a + right in front of the red wire that can't be seen in the pictures.

[strat56]

It works, sounds pretty good.  This is a very high gain pedal!!

[jimilee]

Yep, emulates the Mesa boogie dual rectifier.


Sent from my iPhone using Tapatalk