Success story for mysterious hum removal

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Author Message   Brad K Posted on Tuesday, January 13, 2004 - 04:34 pm:    I own 2 nearly identical HD130 heads (both with the 12AX7 inverter). I replaced the tubes and adjusted the bias on one of them and everything checked out as far as voltages, but when I buttoned it up and turned it on, there was a hum that wasn't there before. I took it apart again, but I just couldn't find any evidence of faulty components- I was thinking I may have a bad filter cap, but thankfully I decided to try it one more time before I took any of those out. With the amp still out of it's case, I turned the power on, and it worked without any hum. I guessed the reason it worked was that the power cord was routed too close to the choke coil or the capacitors in that area. I looked at where the cord was routed on the other amp I own and it was different. I relocated the hardware that holds the power cord to the side of the amp case to the correct position, buttoned it up, and it works perfectly now. Same wonderful supper-clean HD130 sound I enjoy with my other amp. Just wanted to share this with anyone who might have a slightly mysterious hum they can't seem to track down.   Steve Kennedy Posted on Wednesday, January 14, 2004 - 06:59 pm:    Thanks! Good tip. These sorts of things can drive you nuts!