A little signal... lots of hum with cable plugged in.. help!

[NeveSSL]

Hey all!  I just built a BSIABII and I can't get it to work.  The sound that comes out of it suggests that all things are working (the tone alters the sound of the "hum" coming out of it and the drive alters the amount of hum, as well as the level), but it doesn't seem to get any guitar signal.  

Acutally, there is a very, very, very faint sound if I tap the end of the cable with everything maxed.  Any thoughts on what could be wrong?  

This is the first build I've done with a board I etched myself, so I'm hoping that's not the problem... lol... thanks!

Brandon

[powerplayj]

I had the same exact problem a week or so back.  It turned out that one of the legs of a cap had come loose.  Of course, a losse leg is much easier to diagnose than a cold solder joint.  Good luck, you will love this build.

[NeveSSL]

Thanks for replying.  

Loose as in how?  I really hope it doesn't take a lot to get this thing trouble-shot, I suppose you could say... hehe.  I really anticipate hearing this pedal.  Maybe I should go over my solder joints again?

I will try going over the circuit and maybe even all the solder joints.  Something's gotta give sometime soon!  Anyone have any ideas?

Thanks!

Brandon

[smccusker]

sounds like a grounding problem to me (though i admit, my experience is very limited)

Check all your offboard wiring, and that everything that's supposed to be grounded is.

[petemoore]

Input continuity check...not bad to cable up a jack, then, clip a DMM lead to the cable tip and touch the other end to the tip lug on the jack or input of switch to see if the cable tip you'd plug in your guitar is actually inputting to the circuit [and not ground] from the cable tip...
 do the same for the output, all the way to the inserted cables other plug tip.
 It does sound like a Ground or signal path issue.
 Connect your thumb to the output and work through the circuit's signal path to the input, taking voltages of the transistors pins always tells a tale of bias.

[powerplayj]

Just to eliminate the obvious, you did optimize the trimmer pot?  Correct?

[powerplayj]

A bump for the BSIAB2


Mine hums at higher gain settings.  I still can't tell if it is a grounding problem or just the natural character of the pedal.

[NeveSSL]

Hey guys... thanks for all of the replies... I finally got around to probing around with my DMM tonight and discovered that I think my AC Adapter lied to me.  Apparently it's putting out 13v instead of 9!  BUT, it works great with my TS-808???  Not sure on that one, but I do know that it made the transistors voltages higher.

I went through the grounds on the cable and also double checked my wiring, and everything seems correct.  Could I have destroyed a component with heat, perhaps?  I have no clue what to do from here.  Any ideas?  Thanks!

Brandon

[Paul Marossy]

When you increase the supply voltage on a high gain pedal, you'll also increase the noise floor (noise/hiss/hum). Also, a poorly filtered wall wart will give you all kinds of hum. Have you tried it with a 9V battery to see what affect that has?

[NeveSSL]

Thanks for the reply, Paul.  

I haven't had any problems with my TS-808 with noise, but I don't have room for a 9v battery (my first build and I completely miscalculated... lol), so I've not tried one.

Would that make the BSIABII malfunction, though?

Thanks again!

Brandon

[Ge_Whiz]

...discovered that I think my AC Adapter lied to me.  Apparently it's putting out 13v instead of 9!  BUT, it works great with my TS-808???  Brandon

Fairly typical of a poorly regulated adapter. The DMM won't load it down (it draws virtually no current), so the voltage reads higher. When plugged into a circuit with significant current drain, the output will drop to nearer 9V.

[NeveSSL]

It's actually at about 13.7 with no load, straight into the DMM.  It's at about 12.4 or so in the circuit, under load.  Is that still normal?  I know it knocked up the voltage readings on the transistors... heh.  

But, still, the actually problem lies somewhere else, I do believe...

I need to build a good power supply... I've got the transformer and regulator, I just need to make up a board for one and stick it in an enclosure... hehe.

Anyways, thanks for the reply.  

Brandon

[Paul Marossy]

I haven't had any problems with my TS-808 with noise, but I don't have room for a 9v battery (my first build and I completely miscalculated... lol), so I've not tried one.

Would that make the BSIABII malfunction, though?

Try a 9V battery with it temporarily. I am willing to bet that your hum is coming from the elevated supply voltage and the wall wart itself.