ProCo RAT White Face (1985)

Here is a pedal a customer sent me for repair: a vintage ProCo Rat from 1985! This 30 year old little monster had some troubles with switching, happens that the switch that had been changed made some false contact with the (rusty but still conductive) metallic enclosure. 

It is a classic RAT2, produced in 1985. It is called "White Face" RAT because of the white background of the "RAT" logo. Later versions have a dark background with white lettering.
ProCo RAT white face 1985
The RAT is one of the first distorsions ever made. It was created in the late 70s by Scott Burnham. He was a tech working at ProCo, a super small sized company in Kalamazoo. He was working in his basement, with the rats, hence the name of the pedal!

The RAT has been declined in several versions. The first version, "The Rat", was handmade in Kalamazoo, in a small production manner (like you and me making DIY pedals!). The demand rapidly increased, and the production was switched to an industrial process. "The Rat" was produced from 1979 to 1983. In 1983, the enclosure was changed to a smaller sized one, and the ProCo RAT2 was issued. It is this one!
ProCo RAT white face 1985
It has three controls: distorsion, volume and filter. The filter knob acts as a reverse tone knob. The more you drive it to the right, the less trebles you will have. Input and output are on the top of the pedal (top mounted jacks is the best!). The DC jack input is an old style one, not really useful today where most of the power supplies uses 2,1mm Boss-style jacks.

Since its realease, the RAT pedal has been used extensively by many guitarists. Among the most famous are Kurt Cobain (Nirvana), Jeff Beck, Radiohead et Sonic Youth guitarists or Graham Coxon (Blur). You can see that it has been used a lot in the indie scene. It is an agressive distortion sound, full of harmonics that suits very well grunge music for instance!
ProCo RAT white face 1985
The RAT is still in production, with a red LED in the "RAT" logo. It has been declined in several versions. The original RAT uses standard 1n914 silicon diodes, whereas the turbo RAT uses LED for the clipping. Finally, the "you dirty RAT" latest version of the RAT uses 1n34A germanium diodes... You can use a rotary switch to have all the versions in one pedal!

ProCo RAT white face 1985 
Inside this black box, we can find the classic Motorola LM308 chip, that is now quite difficult to find, and quite expensive too! It is a simple double OP-amp, which provides some of the unique characteristics of the RAT pedal. Today, RAT pedals features a different chip, the OP07DP from Texas Instruments.
ProCo RAT white face LM308N IC
The vintage RAT was reissued with the LM308 chip. In 2010, ProCO even reissued this precise 1985 white face RAT!

Here is a great schematic that sums up all the differences between the different versions of the RAT pedal (click on the image to read it better):
ProCo RAT versions schematic
I hope to release a video soon to show you the sound of this vintage RAT!

To go further
History of RAT pedals (official RAT website)
Scott Burnham interview in 2012 (New York Time magazine)
Circuit analysis by Electrosmash: excellent! Really detailled analysis of the circuit and its variations.
History of RAT pedals: pictures of all the models of the RAT pedal. (here is the RAT2 page)
Manual of the RAT2 (pdf)
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Having crazy oscillation probs w old RAT (board says Rev. C 1981, pots date 77). Customer replaced broken switch & then claimed no output. Rewired all switch connections. Noticed 47 Ohm resistor (1st thing 9v supply hits) was cooked. Replaced that. Could that have come from a reverse polarity power supply jack? Both open on bench & reassembled in box oscilations start as soon as u turn up Dist knob. This is intensifies by Filt (reversed). It is completely unbearable & unusable. Any ideas?? i thougt a reverse power suplly jack might have fried the 47 resist-- could this have damaged LM308?

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