Beginner needs advice

[Jordash]

Hi guys,

I'm new to electronics and stomp boxes.

As my first project I've built a beavis board type prototyping rig. So far so good.

The first circuit I tried was a fuzz face, but due to only have high gain transistors (200-300) sounded horrible, but definitely did something!

My next project was to follow the "breadboard a vintage ic distortion" on small bear electronics. So far I've put together the voltage divider network and that works fine.
Then I went about putting together the preamp/boost stage, with a j201. I have set the jfet voltage to 4.5v on the trim pot.
When I go to test this stage, which it says should get a nice clean boost, I get a big cut, and virtually nothing from the top 2 strings. I'm pretty sure I've made a mistake, but can't see where. I've checked component values and polarity and nothing seems amiss, but it just isn't working.

Has anyone got any advice or debugging tips?

[R.G.]

Were you careful to test which pin was which on the JFET? Getting the wrong pin arrangement is a classical mistake, and one I've personally made many times.

[rousejeremy]

There are pinouts and other useful info in this document. http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=42803

[Jordash]

Thanks for the quick replies. That link looks really useful.

I'm pretty sure I've got it the right way around, but I'll check it when I get back home.

[Jordash]

Ok, I've got home and checked my schematic, circuit and data sheet. The jfet is correctly mounted and wired in.

I have a drain voltage of 5.13 and a gate voltage of 2.6. The source is at 0.

The power supply is 9.00v the voltage divider is giving 4.5v either side.

Still very little sound coming through and nothing at the top end.

[petey twofinger]

did u flip the jfett , just to try it ?

[smallbearelec]

I have a drain voltage of 5.13 and a gate voltage of 2.6. The source is at 0.

I took this apart, unfortunately. And I really should have noted what the voltages look like at each pin rather than just the drain. I can say for sure that the source should Not be at 0. Check carefully that neither the source pin nor R7 is mis-wired. Make sure both visually and with your meter if necessary that r7 actually is grounded on one side And seeing the source on the other.

Regards
SD

[Jordash]

Ok guys, ill have a look when I get the chance later.

Btw, thanks for the good guide its been a great help getting into building stomp boxes.

[Jordash]

Ive rechecked the voltages on the jfet:
D:5.23
S:2.64
G:1.64

Im still getting no gain and none of the higher freq

[Jordash]

Found it! It turns out that the 3pdt switch was broken. One of the 'channels' on the foot switch was joining all 3 contacts together. This was at the connection to switch between pedal signal and bypass, therefore it was just mixing the actual signal with pedal signal, hence the weird results. Ended up just cutting the bypass link on the switch, so now it's just an on - off switch. Not ideal, but for the prototyping board it's not the end of the world as I can just join input and output lines to check the clean signal.

Cheers for all the responses I got.