Colorsound - Power Boost / Overdriver

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
RnFR
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Post by RnFR »

yup, I've had this same problem. it was fixed by adjusting transistor bias to 1/2 Vcc on the collector.
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Post by pandadandan »

RnFR wrote:yup, I've had this same problem. it was fixed by adjusting transistor bias to 1/2 Vcc on the collector.
Thought as much. The full-bore sound is f'kin awesome though. Luckily I was tuned down to B standard with my LP when I plugged in so I was set for the doomtone :lol:

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Post by Effectedone »

Hey Guys!

I am new to the forum and about a week ago I decided I wanted to build a Colorsound Powerboost. I found this Old Scematic from 1971(14-6-71) that I followed to the T. The result was alot of popping and such. It did produce a fuzz like distortion but the crakling was very non-musical! So my research lead me here to this forum to find that I was not alone with this problem! I tried using a 1M resister to ground on the input side to bias the transistors to 5V and still the same problem. I used 2n3904 trannies. It became very frustrating. I then found all these different variations on this forum, and my head was really spinning :scratch: . I basically want the closest thing to a Gilmour tone and only want to build it once! I want to know what version seems to be reliable to the print and close to that tone. YOUR OPINIONS PLEASE!

Mike

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Post by Electric Warrior »

For Gilmour you probably want the 18V version.

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Post by Effectedone »

Thanx Electric warrior! Do you have a link to that schematic? Have you had sucsess with this build? Thanx again for the speedy reply! :D

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Post by Electric Warrior »

Check my schematics on page 6. Haven't built one yet..

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Post by yeeshkul »

Electric Warrior wrote:For Gilmour you probably want the 18V version.
I asked Bjorn from gilmourish.com for the same thing, his opinion was 9V.

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Post by Electric Warrior »

Did they make 9V power boosts? I haven't seen any yet.

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Post by Effectedone »

I have yet to see any other Powerboost schematics other than the one Electric warrior posted. Most of the ones I have seen are the overdrive schematics, Like the one from '71 that I originally used. There is a link a few pages back to a Powerboost '96 but the link was dead! I am dying to build one of these that does what it is supposed to do! Not snap crackle and pop LOL :popcorn: !

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Post by RnFR »

it's pretty much the same thing, just different voltage and the overdriver has that tiny collector resistor on Q3, which was my problem. you want to adjust it to the power rail. increase it until you reach 4.5V if going by the 9v version. I think I got as high as 18k, or maybe 8k? can't remember, it's been a few years.
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Post by Effectedone »

Does anyone know where ther may be a hidden link to the 9v powerboost schematic?

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Post by Electric Warrior »

They're labled "Overdriver".

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Post by Electric Warrior »

Scored a Power Boost recently. Here are some photos:

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I restored it back to 18V:

Image

It seems like these early units came with PP4 batteries. The later ones with the PP3 clip had an additional terminal on the board where the battery clips connected with each other.

Only difference to my schematic is that it has a combination of 6.4µF, 4.7µF, 22µF and 25µF electrolytics instead of the usual 4.7µF and 22µF or 6.4 and 25µF, but no big deal.
Transistors are BC184L.

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Post by Ralph78 »

I`m trying to building this pedal, but using the original layout. I´m trying to figuring out what kind of task is making that 1k resistor at the bottom of the PCB...(above the GAIN pot). The Original schematic doesn`t got that resistor.....

I would apreciate if anyone can measure the PCB of his pedal. I wouldn´t finded any measurement of the original PCB and/or the case. That would be great for me (and for the DIYer comunnity).

Thanks friends, you are awesome.

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Post by PokeyPete »

Ralph78 wrote:I`m trying to building this pedal, but using the original layout. I´m trying to figuring out what kind of task is making that 1k resistor at the bottom of the PCB...(above the GAIN pot). The Original schematic doesn`t got that resistor.....

I would apreciate if anyone can measure the PCB of his pedal. I wouldn´t finded any measurement of the original PCB and/or the case. That would be great for me (and for the DIYer comunnity).

Thanks friends, you are awesome.
Ralph, the Overdriver and the Power Boost seem to have some minor differences. The pictures above are of a Power Boost,
while your "Original" schematic is of an Overdriver. That 1k resistor is the emitter resistor of TR3, 470R on your schematic.
My best advice is to go back to page 6 of this thread; about 1/3 of the way down.....Electric Warrior submitted three schematics.
The top two are of Power Boosts and the bottom schematic is of the Overdriver. Compare the Overdriver to your "Original" and
you will find a little different wiring scheme. You may want to consider this change when you build yours.

I compared the components in the pictures against the top schematic and they were exact, except for the three 4.7u capactors.
I couldn't tell exactly, but I believe the two small blue caps are 6.4u and the small green is probably 4.7u. You can guess which
caps would be substituted. Hopefully someone can give you the dimensions you are requesting.
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Post by sinner »

Here's two Power Booster variants as per EW's schematic

15 pitch vero recommended

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Post by sinner »

...and the Overdriver

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Post by monkeyxx »

perfect timing for me on the power boost layout! I finally got around to it, and was smart enough to check here first before diving into a layout

it's a perfect layout with the minor gripe that in all three your gain/volume pot is wired backwards, that was the only error I found.

Here's an updated verified layout for anyone wanting to build the earliest 18V Power Boost... too late to jam but looking forward to using this a lot. It's got a great punchy smooth midrange to it, and with the master volume control added, a lot of control over the sound. The linear gain/volume pot is a bit funny that in the last 5% of the turn to full it goes from mild gain to screaming, so I'll probably switch to the Antilog pot as in the reissue Colorsound pedals. I used BC109, since I generally like those.

I built it on small pitch stripboard and ended up with an insanely packed board, so, I wouldn't recommend it necessarily but it did work on the small pitch stripboard. For some reason my caps are freaking huge compared to any pictures I've seen. Do the 22 uF caps not need to be rated higher than 18V? That would allow them to be a lot smaller than the ones I used.

I'm totally geeking out over pink floyd / T rex using this pedal. well here's my build and the layout...thanks sinner.
Power Boost!! 001.JPG
COLORSOUND POWER BOOST early 18v david gilmour version by sinner, nice layout!.png

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Post by sinner »

Thanks bro for spotting out that error, I'll fox it up later today

And I'm glad you like it ;)

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Post by sinner »

BTW, what a huge caps :shock: BC electronics makes low voltage (25-63v) caps of this value in raster not bigger than 1/2w CC resistors ;)

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