Colorsound Power Boost 18v [schematic]

[bettsaj]

Hi guys,

I'm new to pedal building so please be kind

I've been looking on the net for about 3 weeks now for an accurate PCB layout that I can use for etching and schematic to the original version 2 18v power boost. Nearly every search lead me to a 9v Overdriver layout or schematic. I know the differences in the circuit are minimal, but the end result is like night and day. The power boost for the uninitiated has a much larger amount of headroom before the gain kicks in, therefore the boost in volume is cleaner, where the Overdriver breaks up earlier and acts more like a common or garden overdrive pedal.

Anyhoo, I digress..... There's plenty of pictures on the net of the actual circuit board components, here's a picture of the new reissue from the Marcaris web site

And here's an image of an original power boost board

What I'm looking for is a printable PCB layout, and the correct period circuit diagram for an 18v power boost. The best diagram I've found so far on the net is this one, the later version is the one i'm interested inas that was probably the one that Gilmour used That later version.

Has anybody ever built this version..... And what are the pit falls if any are there with the build.

[bettsaj]

As an aside... n the macaris picture the Blue cylindrical 22uf caps.. Where would I get those from? The brand looks like Vishay.... Just curious where I could source those from.

[Electric Warrior]

I guess you'll have to draw the circuit board yourself. Photos of the trace side are around..
Building it just like that may be harder than you might think as you probably can't get the right pots. Colorsound has to custom order them.

Where you should buy the blue Vishays depends a lot on where you are located...

[bettsaj]

Hi Electric Warrior, thanks for the info. I agree... When you check the Macaris web site Stu Castledine says:

used my '72 Power Boost as a reference.

The PCB is a copy of the final 18V version with PP3 batteries. (I think the first one was a reverse board, second was the normal way up, but had the 33k in a different position and no terminal for the common battery connection. EW thinks this third version came about with the switch to PP3 batteries, which makes sense).

258 Pots are sourced from Omeg, custom made. I've gone with a reverse log pot for the Volume. The original ones had a linear pot, but the reverse log gives a better sweep - I think your standard ones have reverse log too?

Transistors are BC184L, as in my original.

So the volume is a reverse log pot.... No news on the value although the schematic reckons on a 10k. The schematic suggests 100k for the other 2 pots. Trannies are simple.

Do you know where I can find a trace photo.. I've looked and can't find one anywhere

Andy

[Electric Warrior]

They may have to get the other pots directly from Omeg as well. I don't think I've seen this particular style for sale anywhere.

[Electric Warrior]

and here are the pics:
http://files.effectsdatabase.com/gear/p ... st_005.jpg
http://files.effectsdatabase.com/gear/p ... se_001.jpg

[bettsaj]

Thanks for that...... As an aside, who did the soldering??? Stevie Wonder??

[bettsaj]

Update: I've managed to acquire the blue 22uf cylindrical caps........ I've 20 of them if anyone is interested.

[bettsaj]

and here are the pics:
http://files.effectsdatabase.com/gear/p ... st_005.jpg
http://files.effectsdatabase.com/gear/p ... se_001.jpg

Thanks for that... I've just found your post regarding your own PB. You have an early version with the 10k resistor.

Can you tell me what the values of the circled caps are.. The polyester cap I can't make out the colour code.

[deltafred]

The tropical fish caps are the same as resistors only in pF.

brown, black, yellow (104) = 100000pF = 0.1uF
brown, black, orange (103) = 10000pF = 0.01uF

Taken from 1968 Mullard Data Book the bands are.

1 - first capacitance value
2 - second capacitance value
3 - multiplier
4 - tolerance, white = 10%, black = 20%
5 - working voltage, it just lists red as 250V d.c. but IIRC yellow = 400V d.c.

A nice picture of it here viewtopic.php?f=43&t=5253&p=57511&hilit=+mullard+fish#p57511

[bettsaj]

Yeah.. Thanks for that. I've cussed out all of the tropical fish caps except the one circled.....

[bettsaj]

looks like the first 3 colours are red yellow and black.... 24??

[deltafred]

Yeah.. Thanks for that. I've cussed out all of the tropical fish caps except the one circled.....

Sorry, looked at your photo and didn't see the circles. Still a bit zonked out after last night's gig.

To me it looks like a 0.22uf, the 2 red bands form one large one with yellow underneath.

[bettsaj]

Copy that... red red yellow black red... 0.22uf 20% @250v

[Electric Warrior]

The tropical fish caps are the same as resistors only in pF.

brown, black, yellow (104) = 100000pF = 0.1uF
brown, black, orange (103) = 10000pF = 0.01uF

Taken from 1968 Mullard Data Book the bands are.

1 - first capacitance value
2 - second capacitance value
3 - multiplier
4 - tolerance, white = 10%, black = 20%
5 - working voltage, it just lists red as 250V d.c. but IIRC yellow = 400V d.c.

A nice picture of it here http://www.freestompboxes.org/viewtopic ... ish#p57511

the small blue caps are 6.4µF, the small green one is probably a 4.7µF and the large green one is a 22µF.
The exact value probably doesn't matter that much, electrolytics have fairly large tolerances, anyway. They used anything from 4.7µF to 10µF for the smaller electrolytics.

[bettsaj]

Blimey!... They're very different.

So on my BoM I have the following (which is taken from the later version schematic above)

Resistors Qty Metal Film Capacitors (Axial) Qty Polyester Capacitors Qty Transistor Qty Pots Qty
470 1 22µf 4 0.1µf ±20% 250v 2 BC184L 3 100k linear 2
120k 1 220pf 1 0.01µf ±20% 250v 2 10k rev log 1
12k 1 10µf 2 0.22µf ±20% 250v 2
150k 1
180k 1
1k 1
1k2 1
1k8 1
33k 1
39k 1
3k9 1
4k7 3
5k6 1


Where would the 6.4uf, and the 4.7uf sit in the circuit above.....??

[bettsaj]

I think I need to trace the layout in eagle... and then place the components in it to see where they go...

[bettsaj]

Tropical fish caps on order

[bettsaj]

Just a quick question....... Any idea how big the PCB is?.... Like the actual size of the board?

[modman]

No idea. I could measure mine, but you might as well straighten a photo out in Photoshop and use caps and pots as a size reference.

This may come in handy: