Re-housing a ProCo Brat

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.
Post Reply
User avatar
Mr.Grumpy
Breadboard Brother
Information
Posts: 53
Joined: 29 Apr 2010, 15:26
Been thanked: 2 times

Post by Mr.Grumpy »

I'm rehousing my ProCo Brat (aka RoadKill distortion) into a standard Hammond stompbox. The circuit card fits in nicely, but I've had to remove the PCB-mounted input/output jacks. I've also clipped off the 4 diodes in the feedback loop, to try to bring the thing closer to a RAT.

I'm going to leave it with electronic switching and bypass for now. I've noticed when using the Brat previously, that it *POPS* when switching. :slap: Actually more like a click or thud, but you get the idea. Is there any way to stop this noise when it switches? Every other electronically switched pedal I've owned makes no noise when switched. I'm wondering if changing the value of the timing components in the flip-flop circuit might help. Anyone know?

Also, there appears to be a place on the PCB and traces for a status LED, but of course one isn't fitted. One leg of the LED goes to ground, the other goes to a trace that's sized for a resistor, then a trace to a place for a transistor. Has anyone tried to fit a status LED to a BRAT?

I'll post some pics later. Thanks for any assistance.

User avatar
JiM
Diode Debunker
Information
Posts: 967
Joined: 11 Mar 2008, 22:56
Completed builds: Completed builds :
Proco Rat
MXR MicroAmp in a volume pedal
TubeDriver (w/ NoS russian tube and big muff tone contol) + Phase 45 (w/ univibe cap ratio)
Dallas Rangemaster (w/ noisy OC75, negative ground)
SubCaster tube booster (w/ NoS russian tube, PtP)
Hot Harmonics
Music From Outer Space SubCommander in progress
Crackle Not OK
Simple bass blender in a 1590A
Bazz Fuss with a photo-darlington
Location: France
Has thanked: 70 times
Been thanked: 66 times
Contact:

Post by JiM »

Mr.Grumpy wrote:Also, there appears to be a place on the PCB and traces for a status LED, but of course one isn't fitted. One leg of the LED goes to ground, the other goes to a trace that's sized for a resistor, then a trace to a place for a transistor. Has anyone tried to fit a status LED to a BRAT?
I suppose it's intended for the first schematic on this article : http://www.geofex.com/article_folders/m ... millen.htm
I only give negative feedback.

User avatar
Mr.Grumpy
Breadboard Brother
Information
Posts: 53
Joined: 29 Apr 2010, 15:26
Been thanked: 2 times

Post by Mr.Grumpy »

Finally, I've made some time to put towards this project. Should be finished in a few more days. :)

Image

BRAT PCB and it's new home, a cast-aluminum Hammond enclosure. Much to my embarrassment, I discovered that a 9v battery won't fit inside the enclosure when the PCB is mounted. :slap: :block: Oh well, it looks like this pedal will be AC powered only. :| Time to start building (or buying) a pedalboard. Note that the board-mounted input/output jacks were removed and hand wired jacks are put in their place. The hammond enclosure is slightly wider than the original box.

A close up of the BRAT board...
Image

The 0.22 ceramic caps were replaced with "greenie" film caps. Most importantly, the 4 diodes in the feedback loop were clipped off. THIS ALONE IMPROVES THE TONE OF THE BRAT 100%! :applause: I don't have a RAT to make a direct A/B comparison, but to my ears the sound is much improved and the same or very close to the RAT sound!

I also managed to get the status LED circuit working! :idea: I tested it with an LED "pilot light" and it worked, but I have to buy a "loose" LED for the permanent installation. I'm not sure yet, but the "status" may be backwards - LED on when the effect is in bypass mode. I'll find out later today...

User avatar
Mr.Grumpy
Breadboard Brother
Information
Posts: 53
Joined: 29 Apr 2010, 15:26
Been thanked: 2 times

Post by Mr.Grumpy »

It works! :thumbsup The status light works too, the only problem is the LED still glows dimly when the unit is in bypass (remember it's electronic bypass). Apparently the LED I bought has an internal dropping resistor, but I think it's for 5v logic circuits so anything higher and you still need a dropping resistor. It sounds great but it is picking up some noise from my cheap power supply. :? Gives me an excuse to make a pedalboard now...

Pics will be added later.

User avatar
Mr.Grumpy
Breadboard Brother
Information
Posts: 53
Joined: 29 Apr 2010, 15:26
Been thanked: 2 times

Post by Mr.Grumpy »

And it's done. :) Well, almost. I suppose I will eventually get around to using my decal paper from smallbear and putting some graphics on there. Only 'problem' is that the LED doesn't go completely dark when it's in bypass mode, it still glows very dimly. :scratch: I purposely chose a larger than spec'd resistance to dim the LED down a bit, and it's on it's just right - not too bright and not too dim.

Image

A gut shot... Note the clipped off diode leads on the lower left corner of the board, and the LED leads sticking thru the board.

ImageImage

Sounds like a RAT to me... [smilie=a_whyme.gif] Even my fairly inexperienced ears could tell it's a buffered bypass, guitar seems to have a little more bite when it's in line.

User avatar
manganachi
Information
Posts: 1
Joined: 03 May 2011, 02:19

Post by manganachi »

Dear Mr.Grumpy, im from argentina and ive got one of these proco brat. Im really rookie about electronics, but my aim impulse me to do mods sometimes. I wana ask you about those mods, principally the led mod, ive done some milenium bypass in a cry baby (and i add a true by pass with a dpdt too), but in these case can you point me the correct place to connect the control of the transistor. (in the best way, if you can, can you pint me the most mods, in the way a dummy boy culd understand)
Thank for "listening to me"!

Post Reply