WHA WHA NOISE- HELP

[Rhandy]

Hi GibsonGm!

Many thanks for all your help.

I decide put my tube amp in the hands of specialized tecknic. his my friend... after that i POST one anwser.

[GibsonGM]

Very good, Rhandy!  I am glad you'll have him look at it for you.  In time, you will learn to do this for yourself, but for now, it is a good idea

Let me know what is wrong, I am curious!! 

[Rhandy]

Hi GibsonGm!

Today I put my amp in the hands of one friend, is electronic engineer and repair lots of tube amps.

First thing we see is one loose connection on input jack to ground. After look at shematic when you disconect jack amp should mute and bypass to ground, we make one simple test. connect one jack with ground and pin connected, and we have to shake jack for make ground conection and silence the amp. without open amp yet we detect lost or failure connection to ground on input.

My friend show me one very good web site for shematics, I dont now if you know or not but just in case. see it http://bmamps.com/Tech_sch.html

Other important thing, in shematic input jack and output jacks are are ground and we test with multimeter, and we dont have connection. Ground Failure.!!! As you tell me before!! :-)

[GibsonGM]

   It almost always is something simple...I am happy to hear this!!!   Rock on Rhandy    

Now you know the sound of 60Hz (or 50Hz where you are!) buzz...which most always means a bad ground or failed filter caps....

[Rhandy]

Simple things broken your head!!! 

Thank you for all!!

[GibsonGM]

You're welcome!   This is how you learn - in time, you can also learn the skills to fix these things yourself

[Rhandy]

What a hell?

Why now my wha could make some hum on truebypass and without any power supply connected?

[thermionix]

   It almost always is something simple...I am happy to hear this!!!   Rock on Rhandy    

Now you know the sound of 60Hz (or 50Hz where you are!) buzz...which most always means a bad ground or failed filter caps....

Bad bias supply filter caps = 60/50Hz hum.  Bad B+ filter caps = 120/100Hz hum.  Full wave rectification doubles the frequency.  120Hz is close to the B flat on the A string, 1st fret.  When you hear this, you know you need a cap job.  60/50Hz hum could result from a number of issues.

[GibsonGM]

Yes, if it's full wave rectified, and if in fact we're talking 120Hz rather than 60Hz (hard to tell by writing, altho your Bb is a good idea, Thermionix!).  I personally never thought of using the actual frequency as a diagnostic - good call! 


Re. the wah,  "Hum on bypass" means to me, most likely, a bad ground somewhere in your switching at the wah OR it is picking up some RF interference, Rhandy, unless it does this without the wah connected, too?   Then, bad ground in one of your cords, or amp jack again.   The simplest explanation is usually the right one - try a process of elimination....