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Peavey Rage 108 Footswitch Mod

I got my electric guitar back in 1987. As a kid with not much money and no job, I was intent of minimizing cost as much as possible. So I figured I didn't need an amp; I could just play it through my stereo. But after attempting that for a while, I learned that an electric guitar played through a stereo sounds nothing like Jimmy Page, or Steve Howe, or any of the other electric guitar sounds that I loved.

Years went by, and I eventually learned that the amp was an important part of making an electric guitar really rock. (I hadn't discovered effects yet---that came later. Bwahahahaha!) I was still on a budget, so I went for the cheapest amp I could get my hands on. Some time in 1991, I think it was, I went to Whittaker Music (with my grandmother, if I remember right) and bought a Peavey Rage 108. This was back in the days of the Gorilla amp---remember those? The Rage 108 was similar and about the same price, but seemed somewhat better constructed to me.

It turns out that this $100 amp is actually a nice little amplifier. You can get some decent sound out of it, and the distortion channel sounds good and crunchy. When you consider how small and lightweight the thing is, it's a pretty handy piece of equipment.

But, the one thing that always frustrated me about it was that it's hard to switch channels on it while playing. The channel selector switch is a tiny little toggle switch nestled in between two knobs. So you either have to set the amp up where you can easily reach it with your hand while you're playing (and even then it's a pain), or you need to try to poke at the switch with your foot, which is more likely to spin the adjacent knobs and mess up your settings.

So what I really wanted was the ability to switch channels with a footswitch. I searched around on-line and didn't find any information about mods for doing this, so I decided to dive in and figure out how to do it on my own.

It turns out that it's really pretty simple to add a footswitch, so here are my notes on what I did to add one to my amp.


Disclaimer: Use this information at your own risk. If following this advice causes your amp to emit purple smoke, it's your own fault, unless you think that's cool, in which case it's still your own fault.

First, you have to get the "head" out of the "cabinet". To do this, you unscrew the four screws on the top (the ones that don't appear to be holding anything on from the outside):

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/top_screws.jpg

(Having the head held in by screws from the top like this seems to be a pretty standard setup for Peavey amplifiers.)

Before you pull the head out, disconnect the wires from the speaker. They are connected with spade lug connectors, so they just pull off. Note which wire is which so you can re-connect it later. You should then be able to slide the head completely out of the cabinet.

Inside the head, there is a circuit board. A variety of things stand in the way of removing the board. You will need to remove the front knobs by pulling them straight off. The jacks have hex nuts around them; use a wrench to remove those. The board is also held in by several screws; unscrew them.

Once the board is loose, you should be able to pull it out of the sheet metal enclosure:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/removed_board.jpg

It will still be connected to the sheet metal by several wires, but you should be able to manipulate it enough to get it to where you can access both sides of it easily. Be extra careful with the speaker wires when pulling it out. they are held in place by a couple stiff protuding connectors which can get caught up on the square hole in the sheet metal, and the sheet metal may nick the wires:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/nicked_wires.jpg

Next, remove the channel switch by desoldering it:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/desoldered_board.jpg

Note that four of the pins are bent over; you will need to carefully straighten them out to remove the switch.

With the switch free, bend back two of the pins, as shown. (You could cut them off, but I wanted to make sure I could undo all this if it didn't work.) We are going to re-route these pins through a jack on the back of the amp. Note that the pins on the top are connected to the corresponding ones on the bottom; this fact will come in handy.

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch_bent_pins.jpg

We will need to run four wires from the switch and board to the back of the amp. I used a four-conductor-plus-shield microphone cable for this. Solder two of the wires to the top pins corresponding to the bent ones:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch_with_wires.jpg

Solder the shield (or a fifth wire, if you don't have a cable like this available) to the center pin:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch_with_wires2.jpg

At the other end of this short piece of cable, we'll add a jack to allow the footswitch to be plugged in. We need a 1/4" tip-ring-sleeve jack with "closed tip, closed ring" switches, like the Switchcraft 14B (Mouser part number 502-14B). Make sure the cable is long enough to reach from the switch to the back of the head, and solder on the jack:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/jack.jpg

Note how the wires are in pairs, with the two white ones "normalled" to each other, and the same for the two blue ones. The shield is connected to the sleeve contact. It doesn't really matter which pair of wires goes to the tip and which goes to the ring. However, it is important how each pair is connected. The wire attached to the channel switch should be the one that is disconnected from the plug when the plug is inserted. The other wire (which will be connected to the circuit board next) should be connected to the plug when a plug is inserted. Verify this with a continuity tester to save yourself headache later.

Back at the switch end, solder the two free wires to the circuit board, in the two holes that were previously occupied by the pins that are now bent up. Put the switch back and solder it in, making sure that the bent pins do not make contact with the exposed part of the wires soldered to the board:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch_replaced.jpg

Be careful not to scratch up your circuit board like I did:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/resoldered_board.jpg

To help ensure you don't nick your speaker wires, I recommend padding the edge of the square hole with some electrical tape:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/tape_sticker.jpg

(Be sure to put your band's sticker on the inside as well! It makes it sound better.)

Mount the circuit board back in the enclosure, and put back the knobs and nuts on the front panel:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/reassembled_head.jpg

Drill a hole in the back and mount the jack. A five-wired jack like this is kind of bulky, so you may have to fiddle with it a bit to get it to fit right.

Now we need to build the footswitch itself. It's just a SPDT switch with a tip-ring-sleeve plug. Attach the plug to one end of a shielded two-conductor cable:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/plug.jpg

Attach the shield to the sleeve; it doesn't really matter which wire goes to the tip and which goes to the ring.

Drill two holes in a small enclosure. One will hold the switch and the other will admit the cable. Attach the switch to the cable, with the common terminal connected to the shield:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch1.jpg

Then mount the switch in place. I like using a cable tie as a strain relief:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/switch2.jpg

You then should be ready to go! Apart from the jack on the back, there is really no sign that anything is different about the amp:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/jack_on_back.jpg

(Also notice how easily the footswitch can be stashed inside the amp.)

The front switch now sits at a little bit of an angle because the wires run underneath it to the circiut board. But it's hardly noticeable:

http://www.cliffmccarthy.net/images/peavey_rage108_footswitch/rage108_front.jpg

When the footswitch is not plugged in, the front switch works like it always did. When the footswitch is plugged in, it overrides the switch, allowing you to change channels without missing a beat.

Rock on!