GGG 4 Output Power Supply Humming

[boogielicious]

I've built the GGG 4 output power supply with the GGG PCB and it is humming.  I'm using the mouser split pack trannies and other parts  recommended with two 78L09 and two 78L18 regulators.  I'm getting correct voltages from the outputs 8.9 vdc and 17.9 vdc.  The solder joints on the trannies are good.  I'm using four bolt mounts with nylon standoffs and lock nuts.  If I press on the center of the board, the humming diminishes.

Are my trannies bad? loose?  Any help would be appreciated.

Thanks,

Scott

[PharaohAmps]

Is the box itself humming, like the physical enclosure?  Or are the effects connected to the power supply buzzing through the amplifier.  If it's the former, then the laminates on your transformer might not be tight.  You could use a new transformer, or you could eliminate the play in the laminate core.  I've had pedals with internal transformers that buzzed like crazy (Tube Works Real Tubes come to mind here) and I successfully quieted them with some RTV silicone sealant, applied to the sides of the transformer and then rubbed in with a finger to fill the tiny gaps in the laminates.

If it's buzzing through the amp, then you probably have inadequate filtering or a ground loop.  There are solutions for both problems, but let's see what the actual problem is before trying a bunch of crazy stuff.

Matt Farrow

[boogielicious]

It is physical humming not through an amp.  I'll try the RTV.

Thanks,

Scott

[David]

Hey, Boogie!

Before you put goop on your transformer, check this out.  It happened to me when I built a power supply that was a lot like yours.

Do you have a thin metal "horseshoe" with prongs on it around your transformer core?  If so, that's a likely source of your noise.  It was for me.  When I removed the "horseshoe", the vibration went away.

[boogielicious]

The trannies are the Triad Parralax Split Pack type just like in the GGG picture, http://www.generalguitargadgets.com/pics/ss-ps4_interior.jpg

It has a paper label around the sides, no metal horseshoe.  Mine are almost touching together.  Not sure where the laminates are to put RTV on.

Thanks,

Scott