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Vintage threads from the first ten years

Pro Jr. mods

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2/26/2000 10:14 PM
giacomo	Pro Jr. mods I'd like to add a bright switch to my Pro Jr. I tried a 120pf cap on volume pot, but it doesn't seem to work (that amp has not a Fender-classic tone stack). Is there another right place to put the bright cap? Thank you Giacomo

2/26/2000 10:26 PM
phil	See if this helps. http://www.mojotone.com/techtip1.html

2/26/2000 11:24 PM
Randy Jamz	If you study your schematic closely, there is already a 100pF capacitor (C2) across the volume pot. Remove this cap from the board and put it on your switch. Not too hard, or else I would have never figured it out!

2/27/2000 9:53 PM
anonymous	>If you study your schematic closely, there is already a >100pF capacitor (C2) across the volume pot. You're referring to the Blues Jr. The Pro Jr. hasn't that cap. But I found that a bright cap works in parallel to the Pro Jr's C2. Is it a safe solution? Thank you Giacomo

3/2/2000 2:08 AM

OOPS! That foot sure doesn't taste very good in my mouth! You are 100% correct, I WAS looking at a Blues Junior schematic. The Pro Junior has a lot of room for adding high end gain, or just gain for the sake of adding gain. Following the schematic, C2 is a 22pF treble peaking capacitor before the volume control. You could add more capacitance here. You could switch in a 'brite' capacitor across the volume control. You could switch in a cathode bypass capacitor across R4 (there isn't anything there now). For another thought, the 250K treble pot can be bumped up to 500K/1Meg. Ditto for the 250K volume control. Try any of these ideas one at a time until you find the effect you're after. Sorry about the first fuck up!

3/2/2000 6:40 AM
Giacomo	Randy, thanks for your help. Giacomo

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