1 meg resistor on input jack

[supro66]

Is the 1 Meg resistor required on the input jacks
I built two Supro 6420 Thunderbolt and no 1 meg resistors were on the original
what do they do

[sluckey]

They ensure the grid has a return path to ground. Otherwise, you are relying on the resistance inside your guitar to provide that ground path. They are not strictly required and many cheap amps omitted them as a cost saver.

I would not build an amp without them.

[tubeswell]

What Steve said.

[supro66]

Ok I will do a remod on all three


I did remove the death caps from the original

[HotBluePlates]

According to the 6420 schematic in the Hoffman library, the Supro already has a 270kΩ resistor to ground, after a coupling cap from the jacks.

So you don't need to add 1MΩ at the jacks. You could replace the 270kΩ with 1MΩ to see if you like the slight difference...

[supro66]

you are right
and I made up one of those schematics


http://el34world.com/charts/Schematics/files/supro/Supro_6420.pdf


also if you look at weatherford schematic he thanks me for seeing a mistake [ Jim Mitchell ]