Damaged my Corned Beef trying to mod it.

mxaniac · Post by **mxaniac** » 14 Nov 2016, 17:01

I posted this in the wrong place the first time. I messed up my Corned Beef trying to mod it. I removed the mods but the problem persists. Original description and link to schematic is below.

https://www.freestompboxes.org/viewtopic ... 10&t=27976

I discovered if I touch the circuit with a metal object anywhere between the low pass filter 1 input on the PT2399 and the tone control knob the problem goes away. This is a fairly significant circuit path that spans multiple boards and through a HEF4053B analog switch. I tried installing a 10 uF capacitor between ground and that circuit, not because that would make any sense but because I sold my circuits book back for beer money in the late 80's (I'm an ME) and I have no idea what holding a metal object and touching a node is doing other than perhaps adding capacitance, resistance, or inductance but it had no effect.

I've tried reflowing as many of the components I changed or near what I changed as possible. Most of them are 0805 SMD which I'm certainly not highly skilled in but not a complete failure at either. I've not had any positive effect by doing this.

mxaniac · Post by **mxaniac** » 14 Nov 2016, 23:25

I misread C10 for C19 and put the wrong value capacitor in. Replacing the 10 nF with the correct 100 nF capacitor solved the problem.

mxaniac · Post by **mxaniac** » 16 Nov 2016, 01:11

I'm hoping someone wouldn't mind pointing out how to add the Feed pot. I can't seem to get a matching schematic to what jovesdies posted here: https://www.freestompboxes.org/viewtopic.php?f=1&t=24567

I've done my best to trace the relevant part of my board out and I've attached the schematic:

CORNED BEEF TinyCAD.pdf: (15.91 KiB) Downloaded 47 times

I tried adding a .1 uF cap and a pot before R109 but the pot doesn't seem to do anything. I'm in completely over my head and mostly just trying to learn from the experience. Any help would be appreciated.

Thanks,

Rich