Need help!! With SANSAMP GT2. Some oscillation going on!

Started by Izzy, December 28, 2006, 06:06:39 PM

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Izzy

Hey guys, I need some help with this Sansamp GT2. I was finnaly able to finish it today. And I tried it It works, I can hear the signal at the output. But some High oscillation is disturbing it. The signal is very low in volume.

I dont know what Is wrong. As far as I know all the voltage are fine. Havent checked the opamp socket yet though. I am using TLC2262 IC.
When I used Audio probe the oscillation starts right at the point shown below in the schematic.

Guys I need you help!



This is my layout, that I followed:





here are pic of the pedal.
http://img329.imageshack.us/img329/19/p1000019sz5.jpg

http://img384.imageshack.us/img384/937/p1000022kt1.jpg

http://img384.imageshack.us/img384/4619/p1000024kw4.jpg

http://img384.imageshack.us/img384/9202/p1000025ik9.jpg

petemoore

  I'm not good at reading layouts, but it looks to me like you have the +/- opamp inputs reversed, the 10k should be going to the positive inputs, it looks like you have it in the layout as 10k to negative input of IC1a, and...V+? ...the other connection from the 10k should be to IC1b's + input.
  Double check me, .. standard dual opamp?
Convention creates following, following creates convention.

slacker

looks to me like IC1 is upside down and back to front. So it's like this
  _____
4|      |5
3|      |6
2|      |7
1|____|8

Not sure how you've made that fit on to the board though unless the layout is showing the underside of the board?
The biggest problem is that pin 8 isn't connected to anything, it should be going to 9 volts.
All the other opamps appear to have the same problem and they've got no ground connection to pin 4 either.


Izzy

Ohh sorry my bad, I havent shown any opamp's ground connection and +v connection in this Layout. I didnt want to make mess in the layout  ;D

On top of that This layout view is from the bottom of the board. So pin no.1  shown  in the picture is actually the Pin no 4. Sorry My bad forgot to tell that

Anyway I found out 2-3 conenction were missing. Now it is working perfectly! And toone is awesome.
Only problem is volume control after 75% starts to act like treble control. and if I put my HIGH on full oscillation starts.

Pictures are in "PICTURE" thread!

Anyway thanks guys!