Building a better Rat trap 2

Just why does Pro Co only make one pedal? Because they got it right the first time. The Rat distortion box is legendary and it sounds killer, in my humble opinion. Okay, okay, Pro Co has made a few other stomp boxes, but they’re all based around the original Rat circuit and the legendary LM308 IC op-amp. The Turbo Rat, the Rat2, the You Dirty Rat, the Deucetone Rat, and the Rat R2DU rack mount are all descendant of the original: the gnarlier then gnarl white face Rat.

This is a white face Rat from around 1984. There are a few cosmetic differences, however, as I put some modifications into this little guy. A fella I knew asked me to do this before either of us realized the value this pedal could have probably scored on the eBay marketplace. So be it… he ended up trading it to me for some other work I did and I’m happy to call it “mine.” One of my earlier forays into pedal modifications, I’m pleased with the simple changes I made.
The main problem with the original Rat is the lack of an LED power indicator. Maybe it wasn’t a problem if this was the only pedal you were running and had gain set to “fucking loud.” This was addressed on the updated version of the pedal, the Rat2. Pro Co invented the “rat bypass” that allowed a DPDT switch to power up the pedal and turn on an LED. Normally this has to be down with a 3PDT or some kind of electronic switching.
Here I was stuck with the circuit as it lay and in a small box. With no room for adding transistors, I decided to replace the original DPDT switch with a 3PDT.
It fits nicely where the old DPDT used to lie and incorporates the existing PCB holes. Unfortunately, I don’t have any “before” shots and can’t find any gut shots that match this particular Rat PCB. The original switch was hard-wired into those holes and doubled as a junction box. That made the wiring of this switch just a tad different than how I would normally do it.
Why are there two access points for + voltage? I haven’t the foggiest. One of the main issues, though, was the ground wire. Ground, or the – voltage, was connected from the input jack to the PCB via that light teal wire. I had to jumper that without a resistor in the way from the foot switch to the PCB. Normally, I like nesting my LED resistor in the foot switch from ground to keep things clean, but in this case, it’s poking out of my + power hole on the left there and connecting to the LED anode. Confused? So am I, after trying to remember shit I did near two years ago.
Did I explain how 9V that most pedals run on will fry an LED? That’s why you need a small resistor in the way. It can go on the anode (positive) or cathode (negative) side. Doesn’t make a difference.
Placing that LED was a bit trickier. Didja see it?
There is no place on the PCB for an LED, so I had to make one. Normally, one could just place an LED holder somewhere on the enclosure, but the Rat has a tight fit inside for the PCB right near the top of the box. I had to drill two tiny little mounting holes and not hit anything on the other side. It had to be done!
From there, I just had to drill the box where the LED would pop out and I was done, right? Wrong. Someone else coined it, and it’s called B.U.M.S. Blind Urge to Mod Syndrome. I wasn’t done because I couldn’t put the soldering iron down.
Well, I had to go and change out the power jack on this pedal… why? It seemed like the thing to do at the time.
The Rat comes with an old style American 3.5mm TS jack for power. This saved some space in old stomp boxes as it allowed the plug to be covered in metal and grounded, while the tip connection was positive. The downside was that if you plugged into the pedal while your source was in the wall, that positive tip could cause a spark. Enter Roland BOSS corporation and their compact series of pedals. They bring in the barrel plug, which has since become the standard. It allows easy plugging in of pedals without sparks and is probably more secure, for/from retarded musicians.
These days, I’d probably just let the fucking plug be and wire up an adapter.
Oh, I’m sorry? You were asking? What’s that switch there in-between the “FILTER” and “VOLUME” labels? I’m glad you asked.
New to the whole modding thing at the time I did this, I scoured the web for everything possible. I saw mention of something called the “Ruetz Mod” for the Rat, time and time again. I had to put it in, because we had to cram as much as possible into this guy. That, and I wanted it to be selectable. And boy howdy, am I glad I did.
Details on the “Ruetz Mod” can be found here by the guy himself who brought it to light. Essentially, it cuts out a part of the frequency control in the distortion. Some would characterize it as smoothing the tone. I might say muddying. Take yer pick. I’m just glad I didn’t snip the resistor as the fella suggested on his site and got it on a switch instead.
First, you have to find the unlabeled 47Ω resistor in series with the 2.2uF capacitor. It changes in Rat to Rat board revision, but it’s usually near the op-amp somewhere. I unsoldered one of the leads and placed a wire therein. I attached another wire to the open lead to go to the switch.
And it’s that easy. Either the resistor is wired into the series or it’s not. It’s even more fun measuring the enclosure to drill a new hole and fit the switch in the tiny gap between the potentiometers. And by fun, I mean not fun. And all that for a modification I ended up not liking all that much.
The final modification was to the box itself, and frankly, much more useful than the Ruetz mod. As any Rat owner can tell you, he or she has lost the battery cover. They’re so rare, I’ve seen only one, and I’ve seen a lot of Rat distortions. This wasn’t as complicated as the RAT2 battery cover I did just a while back, but it does the trick.
That’s it: a bent piece of sheet metal with some notches cut out and a #6 hex-head machine screw. Why is it red? Because the whole pedal was so beat to shit on the sides I painted it all red. I thought it was snazzy, what of it. At least I have a battery cover for my Rat and you don’t.
I’m so stoked on this pedal. I’ve done some A/B with later model RAT2s and with some clones, and while it’s by a small margin, the original edges out the competition. The mods probably ruined market resale value, but so be it. I’m never getting rid of it. This is my go-to pedal for tracking a mean sounding, compressed, and sharp guitar tone. I know, that doesn’t seem important for a bassist to have. But without it, the other bastards in your band won’t listen to your song demo. Jerks.

3 thoughts on “Building a better Rat trap 2

  1. Hi,
    Thank you so much for those very clear and precise explanations.

    I own a Whiteface RAT reissue, and also wanted a LED.

    You're pictures and schematic we're very helpful. I chose a white LED, dimmed with a 4.2k resistor which I put just under the tone pot. I wired the positive side to the board with a white lead and the negative side with a black lead to the switch. I did the same trick for the +9V, as you did, by soldering the +power to the + red wire.
    Works great !

  2. Hi. I have a Proco RAT with LED (original). The footswitch is defect and I want to replace it with a 3PDT switch. Do you have a wiring diagram or som pictures you could send me please?
    I´m having a hard time finding out how to do this. Anything would help..

    Best regards Alf

    1. There’s no need to replace the DPDT switch with a 3PDT. If you’re looking for true bypass, the RAT already has it. It uses a fairly unique system that latches a separate light circuit to the output ground with a transistor switch. When the transitor is NOT connected to ground, the light goes on (effect on). When the transistor IS connected to ground, light off (effect is bypassed). Your guitar signal is unaffected by the LED. DPDT switches tend to be more durable than 3PDT, so I would replace the defective switch with one just like it.

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