Lpb-1 debugging

[piespot]

Hi,

I'm trying to build my own Lpb-1 booster using the schematic i found at beavisaudio.com... I build it on breadboard and it seemed to work fine exept for a big amount of hum... I concluded the hum came from my powersource and the fact that the circuit on the breadboard wasn't shielded... So I decided to solder it on stripboard and assumed i'd get rid of the noise once all was put in the enclosure... Now that it's build, the noise has reduced but the signal doesn't seem to be boosted at all... I've tried to troubleshoot the circuit all by myself but with no result. I also noticed that signal from my guitar still passes without the transistor in the socket...

Any ideas what I'm doing wrong?

I'm new at all this so I'm probably making some real stupid mistakes...

Tnx in advance

[GibsonGM]

Something is probably connected wrong )  We frequently get solder between 2 points that shouldn't be connected, called a solder bridge.  It shorts out components and causes mayhem.

Go back and check that the transistor is oriented correctly (look at the data sheet pinout). Makes SURE there's no solder bridging anything that shouldn't be connected.  Double-check the values of the resistors you used, and how they are placed.   Take voltage measurements as described in the first post on this forum, "Debugging: What to do when it doesn't work".  Post those voltages.  We will help after that; need the info first!  If the parts are put together the right way, and they aren't burnt out, it WILL work )

For the future, make an audio probe. It won't be very useful on a single-stage build like this, but later on....

Stupid mistakes = how you learn to do this well, and later you'll know what is wrong by the 'sound' of the mistake, etc.  Good experiences, roll with it, post back, and you'll get it working!

~MJP

[piespot]

Thanks for the quick reply!

But I had already looked for solder bridges or other shorts in the circuit and also doublechecked the transistors orientation... I had another close look after what you replied and discovered that the socket I use for the transistor gives bad contacts... so by applying some pressure on the transistor, contact is made and the signal gets its boost...

So the problem is solved... I'm going to remove the bad socket and solder the transistor directly to the circuitboard...

Should have checked the socket right away... I'll remember that for future builds! And I'll avoid using sockets as they don't seem very relyable to me...

[GibsonGM]

Sockets are great when you want to try out other transistors or are concerned about heat when soldering. And they work very very well for IC's, always use them there!   But something about those small 3-pin ones....ugh. I never use them, I use a heatsink to keep the FET or BJT, whatever, safe from soldering heat.

There's a great lesson for DIY - 99.9% of the time it's some mistake we've overlooked - doesn't matter if it's your 1st one, or 100th, you may have to spend more time debugging than actually building the thing!!!    Sometimes just posting on here and getting the moral support to go looking even more helps!
Glad you got it running, LPB's are great little boosters   )