Faulty Harmonic Mesmerizer

[Che_Guitarra]

The name of the pedal is a mouthful; Catalinbread Pareidolia Harmonic Mesmerizer. 

Having owned one in the past, I know I have an output problem.  Or more accurately, a lack of output volume. 

Engaged, with the output control fully dimed, I can barely reach parity with the bypass signal.  I remember parity being closer to 12 o'clock on the dial.  On this unit, 12 o'clock on the dial is but a whisper.  The only good news is the fact i is passing signal.  The other controls seem to be working fine.

Looking at the PCB, the solder peaks around the ICs are not the prettiest.  That said, I can't see any obvious faults either.  No solder bridges, no cold solder cracks, and trace continuity appears fine.  I'm yet to pull the PCB from the enclosure for full circuit inspection.

I've contacted Catalinbread but no reply as of yet. 


So... good folks of Group DIY... I'm hoping you can help me troubleshoot this problem.  I'm guessing i'm bleeding signal to ground where I shouldn't be, or i'm not bleeding to ground where I should to be.  But my electronic insight ends there.


Where to start with diagnosing a fault like this?

 

[volker]

Here you can find  the schematic. Start with checking the DC voltages on the transistors and ICs.

 

[Che_Guitarra]

Thanks Volker - I signed up for that forum immediately... needed to do so to view the attachment.

I'm not seeing any reference voltages on that schematic, nor elsewhere in that thread?

Voltages measured across the ICs:
- 8 pin IC, top bank left to right:  7.7, 3.71, 3.71, 3.71.
- 8 pin IC, bottom bank left to right:  3.9, 3.8, 3.8, 0.

- 16 pin IC, top bank left to right:  0.98, 0.98, 1.94, 1.94, 0, 0, 2.94, 1.54.
- 16 pin IC, bottom bank left to right:  0, 3.71, 3.67, 7.71, 3.98, 3.95, 2.92, 3.86.

 

[fazer]

Just read the freestomp thread.  A oscope is your friend.  Output level could be a bad volume pot or the fets could be damaged. You NEAD a scope and follow pink nose or a guitar looper with a riff playing acting as a test signal.  Don’t have one of these pedals but have a board ordered from pedalpcb.com.  Will be a while before I get to it.

 

[Whoops]

Post at http://freestompboxes.org/ and also at  http://www.diystompboxes.com/smfforum/,
those are the 2 best guitar pedals forums

 

[abbey road d enfer]

Voltages measured across the ICs:
- 8 pin IC, top bank left to right:  7.7, 3.71, 3.71, 3.71.
- 8 pin IC, bottom bank left to right:  3.9, 3.8, 3.8, 0.

- 16 pin IC, top bank left to right:  0.98, 0.98, 1.94, 1.94, 0, 0, 2.94, 1.54.
- 16 pin IC, bottom bank left to right:  0, 3.71, 3.67, 7.71, 3.98, 3.95, 2.92, 3.86.

That seems to indicate the IC's work as they should; you need to check the voltages on the FET's.