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FDP Forum / Amp Mods, Repairs, and Projects / Blues Junior Mods...

Matt_Krush

usa

Sep 26th, 2017 05:09 PM   Edit   Profile   Print Topic   Search Topic

Hi folks, new to the forums and to fender amps.

But I'd like to share a few Blues Junior Mods that are not widely publicized...we all know of the BillM mods...Hopefully some of you tweakers find these useful.

1st: the Fat switch. This engages a .22uf cathode bypass capacitor. Want more low end? Solder a .47uf cap in parallel on top of it..or replace it with a .68uf. Heck you could even make it switchable if so inclined.

2nd: Negative feedback. Want more low-end yet? Increase the negative feedback resistance. What I did was snip that purple wire from the output transformer and put a 100k pot in series with it. I can go from stock to lots more low-end..I mounted it on the steel plate that kinda protects the tubes so it's hidden and out of the way.

3rd: A second speaker jack. I don't a foot-switch for my "fat" switch...its just always on. So I disconnected the wires to it (red, white, & green). The red and white must be connected together for the face plate button to work and the green left disconnected. Then I jumpered from the existing speaker out jack to the former foot-switch jack. One could have just as easily drilled a second hole and installed a jack...but I didn't.

My other mods included a bias pot.
I snipped out the 33k (R37) and installed a 10k resistor to a 50k pot in it's place (the resistor prevents a ZERO ohm situation).

And since I started with the base model, I went with a Warehouse Guitar Speaker, the 55hZ Reaper.
I like it much better than the Eminence Lightning bolt. The Celestion 70/80 wasn't bad (its one I had on hand to try). The Reaper gives a nice warm tone and remains clear.

I did replace the EL84 Sovtek (Groove Tubes) with Tung Sols and put a JJECC802 (12AU7) in V1 to lower the gain (this allows me more adjustment in volume in both the pre and post amp areas) and replaced the V2 & V3 with Sovtek LPS 12AX7s.
The JJ5751 didn't lower it quite enough. I need to acquire a 12AT7 or 12AY7 for V1...I think that might be just right.
Clearly this make getting distortion more difficult, so unless you are a pedal user for drive/distortion, you may not want to decrease the V1 gain.

JJuran
Contributing Member
******

Boston Area

Sep 30th, 2017 09:58 PM   Edit   Profile   Print Topic   Search Topic

I miss BillM...

Roly
Contributing Member
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**********
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Whitehorse Canada

I don't get out much
Oct 1st, 2017 05:51 AM   Edit   Profile   Print Topic   Search Topic

Me too.

FDP Forum / Amp Mods, Repairs, and Projects / Blues Junior Mods...




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