Help with Overdrive pedal.

[dweilmd]

I am fairly new to this site (and pedal building) so I hope this is the correct place to post this.  I am built an overdrive pedal based on a TL082 IC. Everything works fine for about 15 seconds then the volume drops dramatically to the point where I can barely hear anything.  On bypass the volume is normal.  If I unplug everything for a few minutes and then try again, the same thing happens.  I have a very limited understanding of electronics and don't really know what the problem is or where to start.

Any suggestions?

[GibsonGM]

Hi, and welcome!      First of all - we need to know WHAT you're building!  Do you have a schematic diagram of it that you can post or link us to?

Is the battery connected? 

Most always, it is builder error that causes stuff like this.  I would check that all of your polarized capacitors are pointing in the correct direction. 

In fact, the first thing we do on a basic kit build debug is to go back over all the connections, and be sure that the solder joints are nice, and that there are no shorts to places that should not be connected (a "solder bridge").   Even with a magnifying glass. The visual check comes first...check all wires going places, be sure they're attached well and going where they are supposed to.  Switch wiring can cause massive issues...

Then, if you have a meter, make sure you have power at the board, and at the IC power pin (careful not to short ic pins together!).

If that doesn't do anything, go here: http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[dweilmd]

Thank you for your reply.

The pedal powers on and all of the pots work fine -- in fact for a cheap pedal i'm surprised how good it sounds.
After about 15 seconds the output level starts fading until it can only be faintly heard -- almost like something is sucking the power out of it. Despite that, the led stays lit and the pedal is getting power.  I took some readings from the TL 082 IC the best I could.

When the output is good (first 15 seconds) I get the following readings:
1.  2.50      8.  3.50
2.  1.50      7.  2.00
3.  1.60      6.  variable 0.5 to 2.0
4.  0.00      5.  2.40

After the output fades the readings are:
1.  0.00     8.  2.10
2.  0.00     7.  1.47
3.  0.79     6.  1.47
4.  0.00     5.  1.40

I don't have the schematics because it was a kit that did not come with them (only instructions), but I want to  include some photos but it is not letting me.

I have also re-floated all of the solder points and checked the polarity of each of the polarized components.  As far as I can tell it all appears to be wired correctly.

I really appreciate any help.  I guess one learns a lot more when things don't go well than if it was perfect the first time. THANKS.

         

[PRR]

> 8.  3.50

We would expect full 9V at this pin. Maybe 8V if there's some stuff in the power feed.

The TL082 needs like 7V to work properly. It *may* "work" at 3.5V; not at its best but not-sucky. 2.1V may be where it just craps-out totally.

Figure where your "9V" comes from and why it isn't holding-up at the chip.

[dweilmd]

Thanks for everyone's help.  I started replacing components between the power source and the input to the chip.  I guess it was a bad capacitor (or bad soldering) because when I changed it out it started working.  Not sure I would have slept tonight if I didn't get it to work.  I'm really glad to have access to this forum !!                                             

[davepedals]

Fantastic!

[phaeton]

Glad you got it working.

Just curious- what kit was this?