Thor trouble

[alderbody]

My Thor (v1.0) build is not working...

Although i triple-checked all connections/pinouts, i don't get any output at all.
I even replaced the chip, but no luck.

No strange buzzes and noises. Just zero output!

I followed Xavier's perfboard layout,
which btw has Q3 as Q4 (in the ROG schematic), and vice versa.

For easier understanding i'll use ROG's naming.

Here are the voltages:

Vcc  =  9.01V
Vref =  4.52V


Q1 
      D: 6.40V
      S: 5.42V
      G: 5.45V

Q2 
      D: 4.51V
      S: 0.30V  0.26V*
      G: 0.08V  0.02V*  (*= WITH GAIN POT @ 'O')

Q3 
      D: 9.01V
      S: 8.12V
      G: 8.15V

Q4
      D: 4.48V
      S: 3.63V
      G: 3.65V


TL071 

       IN-: 4.49V
       IN+: 4.45V
       OUT: 4.49V


Any ideas?

[alderbody]

All FETs are as suggeted by ROG.

Q1, Q3, Q4 2N5457 and Q2 J201.

All parts values are also as close as possible to the schem.

No mods used.

Most resistors are metal film (some are CCs... ), the pF range caps are polystyrene and the other films are Mallory 150 series.

Trimpots are multi-turn for extra accuracy.

Pots are Alpha 24mm.


   

[MartyMart]

Q3's source should be the same as Q4's drain pretty much, as they are connected
Check that wireup of the "muamp" as it's called.
That's your problem area and is preventing proper amplification.

MM.

[stm]

The voltage readings you provided are totally off the scale!

Q1, Q2 and Q2 Gates must be zero volts regardless of the GAIN pot rotation.

It looks like the FETs are not properly installed, like a pinout problem or a broken ground trace somewhere.

[Auke Haarsma]

you may also want to check my debug-thread:
http://www.diystompboxes.com/smfforum/index.php?topic=53763.0

I got it all working now, thanks to the help of this forum. And I love the Thor. I boxed it now, and it's awesome! Best pedal I have built thus far! So don't give up on this one. I'm sure you'll get it working!

[alderbody]

Thanks for your replies, guys.

I'll go check those and get back with my results.

I'm sure it's gonna work and it will be great.


Thanks again.

[alderbody]

Problem solved!!!

.... wrong 2N5457 pinout....      

but i was betrayed by a wrong note i had about it, so i foolishly insisted that this was not the problem, until you opened my eyes!...


thanks guys!


...btw, what a lovliest sounding pedal!!!!

can't wait to try it at normal volume because when i finished it last night it was too late for cranking...

pics are coming...

[MartyMart]

Glad that you sorted it, sounds great eh !!
Enjoy,
Marty.

[alderbody]

Here's the circuit:



and a closeup,

[alderbody]

btw, speaking of "mods"....

would an MPF102 fit in the place of the J201 for a sparklier sound and less gain?
(...as long as the pinout is correct...   )

just a thought...

[MartyMart]

Looks great, just wondering why you wasted those 630v "amp" caps in a 9v
stompbox  !!!   mallory's   !!!! ??
Your caps cost more than my last three builds   

It would be a LOT smaller also using 50v "poly's"   

[alderbody]

I just love overkills!!!   

don't they look great, though?...

[Opencan]

it looks awsome !

can you grab a picture of the bottom of the perfboard?


This is one of my next projects, hope i'll like as much as you do

[Auke Haarsma]

congrats, nice build!