Ralle mod fixes Power Brake!

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vh junkie
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Ralle mod fixes Power Brake!

Post by vh junkie » Thu Nov 19, 2009 7:00 pm

Picked up a PB off the bay... sound like crap when you hit an open A chord with the amp cranked! Weird bounce back buzz coming from the speakers after the A string is struck... turned out shorting the a 160uf cap (essentially removing the LC circuit) fixed it. So I guess the 160uf cap was leaking.

Anyone have any similar probs, thoughts or results from modifying this circuit?

I have heard that this circuit sets the "resonant frequency" for the circuit. I guess I'll order a new cap to if what I think. Any feedback is appreciated!
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Staalhoofd
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Re: Ralle mod fixes Power Brake!

Post by Staalhoofd » Fri Nov 20, 2009 8:48 am

Did the same 'mod' thanks to Ralle. The PB got way better. Was thinking about selling it before the mod.
To me, the PB truely doesn't colour the sound with the LC circuit out. With the LC circuit the bass increases as you attenuate more. I hated that. Now I love my PB :wink:
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Ralle
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Re: Ralle mod fixes Power Brake!

Post by Ralle » Fri Nov 20, 2009 12:24 pm

This would be somthing for all the guys who didn't like the PB :wink: To me the PB is the only one that works as a truely transparent attenuator...
BTW that mod isn't my ide... It was my good friend Lasse Printz who showed me how to do it... In fact he has teached me just about everything I know about electronics...

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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sat Nov 21, 2009 2:39 pm

"...Anyone have any similar probs, thoughts or results from modifying this circuit?..."

oh YEAH. this has been winding me up for ages. my PB sucks w/ the fuzz-hair sound @ low volumes - been like it for as long as i can remember. VHjunkie/Ralle/Staalhoofd, 'shorting the LC 160uf cap' is done just by wiring/bypassing around it?

thanks for the info guys - gear arrives in a few weeks - will open up, search & destroy the 160 and post report results.

Cheers,

J.

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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sat Nov 21, 2009 4:25 pm

... just pulled these pix frm MarshalManiacs '71 post (thnx MM) @ http://bit.ly/8gZAPY -- not sure if the red & black wires in one photo are shorting the 160 or not? maybe they're part of the line-out mod....

J.
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vh junkie
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Re: Ralle mod fixes Power Brake!

Post by vh junkie » Sat Nov 21, 2009 6:02 pm

If you look at the first picture... on the right side of the circuit board... there is a vertical row of pins at the top, and a vertical row of pins near the bottom; on the PB I have there are two pins in between these two... the mod I did is accomplished by shorting this two.

But in these pictures, there is a lead extending downward from there; must be part of line out mod, with a hole drilled from the other side.
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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sat Nov 21, 2009 6:25 pm

gotcha vhj --- i see. looks like long line of solder. i'll have a go with shorting just the two pins in middle.

will post back w/ results when i get PB back in few weeks.

Thnx ---

J.

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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sat Jul 17, 2010 2:56 pm

Hey hey ---

just resuscitating an old thread --- and double checking the PB mod w/ VHjunkie...

I'm about to short the middle light green cap to get rid of the fuzz/fur baggyness thats been driving me nuts when using the PB.

will report back w/ results.... so long as i've got the right cap to be shorted!

cheers, and thnx to VH junkie, Ralle & MarshalManiac

J.
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vh junkie
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Re: Ralle mod fixes Power Brake!

Post by vh junkie » Sat Jul 17, 2010 4:36 pm

Yup! That's the one!

I actually replaces the 160uf cap with a 100uf cap (couldn't find anything closer) ... still no joy!

Do as Ralle does!
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vanhalen5150
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Re: Ralle mod fixes Power Brake!

Post by vanhalen5150 » Sun Jul 18, 2010 8:29 am

So you just short across the 2 terminals? I have one on the way.
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vh junkie
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Re: Ralle mod fixes Power Brake!

Post by vh junkie » Sun Jul 18, 2010 8:50 am

Yup... try it with and with out... might sound OK as is... I think after a while that cap starts to leak and it sounds better with it shorted out...
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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sun Jul 18, 2010 4:25 pm

wahey. def. sounds better.

havent had it up @ live vol yet, but has taken the FLUB/FUR out @ low levels. I left the cap in and just added a jumper - piece of cake. (see pic)

also been trying out an ep-booster. like it....until a ep-3 comes my way.

THNX for the info y'all - vhJunkie, Lasse Printz, Ralle & Staalhoofd. vh5150, you should def. try it out.

cheers,

John.
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vh junkie
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Re: Ralle mod fixes Power Brake!

Post by vh junkie » Sun Jul 18, 2010 8:03 pm

Yup, the only reason I would say to try it both ways is:

a) it an easy mod to reverse
b) Rockstah made some pretty convincing clips without saying he modded it!
"With all due respect, sir, you're beginning to bore the hell out of me."
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zeeb
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Re: Ralle mod fixes Power Brake!

Post by zeeb » Sun Jul 18, 2010 8:20 pm

aahhh. i see. R.stah modded his too? nice one. 8) will try it like this (w/ cap) for a while & see how it goes. it already sounds loads better.

did you notice any big difference with the cap taken out completely? which did you prefer?

cheers,

J.

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Ralle
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Re: Ralle mod fixes Power Brake!

Post by Ralle » Sun Jul 18, 2010 10:19 pm

Just so you know, guys... Remember to keep an extra look out on that effect resistor ( 8 ohm ) in the PB... It gets so hot that the solder points might melt and dissconnect... that happend to me... :evil: and I blew my tranny... just now... Luckly I had another Metro tranny ( remember to allways buy two trannys... )
And I had to take my two effect resistors ( to cover the effect ) from my loadbox and put them in the PB... This time I screwed the cables on there... :wink:

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