Randall rg100 Es ?

[888guitars]

Does anyone know if you plug in the foot switch on the Randall RG100 Es , will it truly separate the channels? With no switch plugged in, you can blend each channel together. I am hoping the switch will completely disconnect the channels from each other.

[The Dude]

It looks like if you have the right footswitch, you can run either channel independently or both together.

[888guitars]

Good! I think there is a bit of signal bleed from each channel without the switch.

[J M Fahey]

Well, you might have a little signal bleed even with a footswitch, although of no importance at stage levels.

Fact is both channels run always, all the time, footswitch just grounds output from one or the other, muting it, but the distortion section is still working, so a little may bleed where it shouldn't through stray capacitance, parallel wires or tracks, etc.

More modern amps , with more complex switching, add 1 or 2 extra muting transistors at an earlier stage, so distortion stops distorting when not used.

[888guitars]

What if I grounded the input to the clean channel with a switch so it doesn't split the input guitar signal?

[J M Fahey]

The system used by Randall is crude, what was used way back then, they plain short signal to ground at the far end of a very long cable, similar to reverb switching in a Twin Reverb.

A modern amp would use a chassis mounted relay to do the switching, with signal wiring only a few inches long, and have only the DC for the relay coil switched remotely, way better.

The relay might have an extra set of contacts to short the dirty channel also at an earlier stage, that would definitely attenuate crosstalk.

[888guitars]

Do the led's on the amp turn on only with the foot switch also?

[g1]

Correct. The channel led's do not work without footswitch.

[888guitars]

Ok now what is the tl064 doing? I don't see it on the schematic? It says in the legend " IC = 4558" . I see a 1458 is in the reverb driver stage which is in the schematic. I don't understand what the TL064 dual fet is for?

[888guitars]

Here is the IC in question

[888guitars]

And the schematic

[J M Fahey]

It can't be a TL064 which is a 14 pin IC, your picture shows an 8 pin one, so ....

And the image is so small/far away that IC markings are unreadable.

It says in the legend " IC = 4558"

Which legend?
On the IC?
On the schematic?
On PCB silkscreen?

Thanks.

[DrGonz78]

Strange... Well perhaps someone mistakenly installed the TL604CP P-Mos analog switching IC?? Did you mean to type TL604 instead of TL064?? The picture looks like the old "silver" Texas Instruments 4558 chip that you find in the old 80's Randall amps, but yes the image is not zoomed enough to read it.

[DrGonz78]

Just another look at that picture you uploaded and I noticed some charred PCB area underneath a resistor. Look at the pic attached...

[888guitars]

Yup oops TL604. Regardless it's not in the schematic?