Debugging Ruby Amp

[mvotre]

sorry for the trouble folks. Tried my best to found the errors myself, but I'm a complete retard regarding electronic schematics (but the plan is to learn how everything works for later projects).

So, I tried a long time ago to build a Ruby. But my soldering was horrible at best. Really dirty pieces and soldering iron, so it was a mess. A few time ago, I got a faulty pot on my guitar (modded by a luthier), and I decided to fix it myself. So, after a LOT of time cleaning the tip of the iron with a wet sponge, solder bliss. Everything flows just fine. So I decided to retry a amp build.

Build in perfboard, following the layout on ROG site http://www.runoffgroove.com/ruby.html

IC and Fet are soldered to sockets. I measured a lot of things, wich shows

IC:
pin 1 and 8 - I leave open. When they say open, it's really open, right? Like soldered to nothing? That's how mine is right now
pin 2  - 0V
pin 3 and 4 - ground
pin 5 - 4,26V
pin 6 - power input - 8,8V
pin 7 - 4,37v

FET
Gate - 8,8V
Source - 0,03v
Drain - 0v

Positive of 100uf cap - 8,8V
Positive of 220 uf cap - 4,26V
Negative of 220uf cap - 0,08v

modifications to the original circuit: I leave pin 1 and 8 open, and put a small 0,001uf cap between lugs 2 and 3 of the pot. But with the original 10k volume pot of the schematic.

Right now I got just noise. The humming for a amp getting interference. The noise changes (reduce) when I turn the volume knob. I just can't get any sound...

thanks in advance, and if you guys need any other measuring, just ask and I will do it ASAP.
also, sorry for some english errors you may find. Not a native speaker 

[anotherjim]

Are you sure FET voltages you show are correctly identified? Gate volts should read much, much lower (closer to 0V) and source and drain each somewhere 3-6 volt. Make sure you've identified the gate terminal of your FET correctly. You can get away with having the source & drain swapped over.

386 pin volts all look ok. If you disconnect the wire to vol pot lug 2 and use that wire for your input, you should get sound from the 386, although quieter without the FET stage.

[mvotre]

well, first things firts.

THANKS! It worked it you "hack". And by the way, it's in a nice volume for my use. Besides, pluggin my distortion in front of it, things get louder, and surprisingly (?) clean. Damn nice!

BUT, I want to make the thing work properly, so I need to figure out that FET. The sad story is: when I tried to build my Ruby in the past, I tried on a breadboard (wich I stupidly gave away), and I remember that after lots of tries building and rebuilding from scratch, I got sound, messing with the jumpers, in a "wrong" use of the fet pins. I got a MPF102, and used the online resource as found here:



and it give the results I posted. It's possible to have a fet with diferent pin out? How can I test the fet in other positions without risking burning it? By the way, since I remembered the mismatched with the first fet (bought at the same store), I soldered a socket in my board, just so I can mess with it  will try to found something and post results.

[anotherjim]

You measured supply volts on your Gate, so I was wondering if you have got it mixed up. The input goes to the gate. Drain connects to supply +, Source to 3k9 resistor...

Apparently you can get components with different pin-outs. You can identify the Gate easily with your multimeter. See RG's answer here...
http://www.diystompboxes.com/smfforum/index.php?topic=76438.0

[mvotre]

yeah, now I see. Sorry for that.

Anyway, will try too measure. But before I read your answer, I was making some pictures with descriptions.





sorry for the ugly job. First one, after all 

[mvotre]

PS: trying the test (if I undestood correctly), my pins are in the correct position, and everything should work as expected