03-07-2016, 01:26 PM
Thanks Liquids, i just tried putting some signal through the ext in jack. With or without the prior V1 and V2 and V201 preamp tubes in place, i get significant noise reduction when i plug something in, (my phone). However, there is still some pretty loud humming and the remaining hum is more in the midrange audio spectrum. I tried swapping V3 and V4 with brand new ones and still get hum.
@AEB-1 : seems like the echo board is grounded by the footswitch jack, but also by one of the standoffs that has a tab screwed on and soldered to the board's ground bus. I tried unsoldering the wire going to the footswich jack with no improvement and the humming... I'm now gonna try cleaning the input jacks and changing the shielded wires to see if I get any improvement on the input section humming. But since i'm getting humming in every stage, i'm starting to suspect that the hum is coming either from the "E" power supply rail or from the heaters... Any idea why tweaking the hum control balance pot isn't doing any change at all on the hum ? Shouldn't it be at least increasing the hum when turned all the way up or down ?
@AEB-1 : seems like the echo board is grounded by the footswitch jack, but also by one of the standoffs that has a tab screwed on and soldered to the board's ground bus. I tried unsoldering the wire going to the footswich jack with no improvement and the humming... I'm now gonna try cleaning the input jacks and changing the shielded wires to see if I get any improvement on the input section humming. But since i'm getting humming in every stage, i'm starting to suspect that the hum is coming either from the "E" power supply rail or from the heaters... Any idea why tweaking the hum control balance pot isn't doing any change at all on the hum ? Shouldn't it be at least increasing the hum when turned all the way up or down ?