Tonepad Rat problem, strange solution that worked but don't know why.

[RattScum]

Hi guys, first post on here but I'm kinda at my wits end so I figured I asked for some help.

I built the La Rata from the tonepad site with an LM308 from Small bear. Everything works but the output is incredibly low. I did a lot of trouble shooting, I even switched around the transistor but to no avail. I checked for solder bridges...none. Then I went over each joint to check for a cold solder....Then I found one. It was the joint on the PCB coming from lug 3 on the volume. I assumed that was my problem so I resoldered it, still low output. Then I tried it one more time being anal retentive. This time I accidentally bridged the joint on the PCB from volume lug 3 and the top of Diode 1 and there it was, very loud output and sounds great!!

Does anyone have any idea why this would work when it is clearly wrong according to the schematic??

Any ideas on what I could have screwed up and how and why this fixed it?

All controls work and it sounds really good, but I dont have a Rat to compare it to so I have no idea if it sounds "right".

Thanks any insight would be appreciated.

[lopsided]

if this happens, it seems like the circuit works fine up to the diodes. maybe recheck the connections between the diodes to the right side. Check carefully the wiring of the filter pot and the following components, if this dosn't work maybe send the voltages of the transistor.

[RattScum]

Thanks, I will check this afternoon.

[alparent]

Did you test the diode...might be bad?

I've also made one those http://www.geofex.com/FX_images/audioprb.gif the best debuging tool I have!

[ACS]

Follow the signal path (which is what the audio probe's for!)

Audio comes out of the IC, passes through the filter pot - in via 2/3, out via 1. 2/3 are connected to your clipping diodes - so this means the clipping is happening prior to the filter pot. By bridging from the 'hot' side of the clipping diodes to the volume pot (which is pretty much last in the signal chain), what have you bypassed? Answer: the whole output buffer section!

So, my guess is that your problem lies there. Perhaps a mis-oriented trannie? Check your voltages around Q2, but there's only really six components in that area, and one of them would appear to be causing this - solder bridge, cold joint, faulty part, something else?

Good luck!

[LucifersTrip]

did you try unsoldering the accidental joint between lug 3 and the top of Diode 1 and see if it reverts to "bad"

[RattScum]

Hi guys, I finally got some time to mess with the pedal tonight.
I unsoldered the lug 3/diode solder bridge and reverted it back to the correct way and again the output was low.

So, I removed the transistor and put in a fresh one and guess what? It sounds nice and loud!
I guess there must have been a problem with the trannie.

Thanks for all of the help guys, very appreciated.