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A good customer asked me if I could make his CRUNCH button on the front of his PV XXX40 work from the footswitch. I always maintain that I can remote any panel control, so I took the work. The existing FS even had a space in the center for an additional push button. Apparently some other model uses the same molding for a five button FS.
Usually the PV Crunch switch just activates a relay or two, which would be trivial to mod. But here, there is a 4PDT Crunch switch. One section of it in fact does operate a relay, while the other three do level shifting or tone shifting. And it needs all of them to toggle for things to work right.
Ultimately what I did was replace the three sections of switch with a couple DPDT relays. Rather than cut traces to the original switch, I replaced the 4PDT switch with a DPDT of the same brand and series. I also lifted a couple small parts that were wired to one side of the switch, so only one half of that DPDT was doing anything. It controls the pre-existing relay.
My two extra relays were mounted with contact cement to the circuit board - there's a large clear area - by gluing their tops to the board, legs sticking up. They fit nicely between the input jack and the Crunch switch. A few pieces of small wire - "mod wire" - tacked on the relay legs then connected those new relays to the pads the old switch used. And two wires went to the two lifted components.
The new switch being in the same series took the old knob properly, and fit.
I wired the relay coils with an appropriate dropping resistor more or less in parallel with the existing relay. SO now the switch rather than directly switching circuit elements, now switches three relays which do it in turn.
Now that I have it down to one switch closure controlling all that stuff, it was nothing to break into the line from the power supply on the way to that switch and insert a cutout jack for the FS.
This amp uses high side switching on the relays, so the FS cannot be grounded. There is plenty room on the rear panel for a jack, just use a plastic one like a Cliff. Only cut one trace for that.
And as a bonus, using the existing FS saved getting abother one-button job. I mounted a #11 on the end of the FS and wired in a new switch.
Usually the PV Crunch switch just activates a relay or two, which would be trivial to mod. But here, there is a 4PDT Crunch switch. One section of it in fact does operate a relay, while the other three do level shifting or tone shifting. And it needs all of them to toggle for things to work right.
Ultimately what I did was replace the three sections of switch with a couple DPDT relays. Rather than cut traces to the original switch, I replaced the 4PDT switch with a DPDT of the same brand and series. I also lifted a couple small parts that were wired to one side of the switch, so only one half of that DPDT was doing anything. It controls the pre-existing relay.
My two extra relays were mounted with contact cement to the circuit board - there's a large clear area - by gluing their tops to the board, legs sticking up. They fit nicely between the input jack and the Crunch switch. A few pieces of small wire - "mod wire" - tacked on the relay legs then connected those new relays to the pads the old switch used. And two wires went to the two lifted components.
The new switch being in the same series took the old knob properly, and fit.
I wired the relay coils with an appropriate dropping resistor more or less in parallel with the existing relay. SO now the switch rather than directly switching circuit elements, now switches three relays which do it in turn.
Now that I have it down to one switch closure controlling all that stuff, it was nothing to break into the line from the power supply on the way to that switch and insert a cutout jack for the FS.
This amp uses high side switching on the relays, so the FS cannot be grounded. There is plenty room on the rear panel for a jack, just use a plastic one like a Cliff. Only cut one trace for that.
And as a bonus, using the existing FS saved getting abother one-button job. I mounted a #11 on the end of the FS and wired in a new switch.
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