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Mods that actually work for fixing Fender Pro jr problems.

klbabcock11

Silver Supporting Member
Messages
308
Hi, I have a PJ 3 and wanted to fix the hum issues. I already separated the wiring and shielding. I have a great new tube set with a 5751 on its way. I also have a 112 cab and speaker it's going in. I am probably going to order the fromel mod kit and install that too. Is there anything I'm missing. Love the little amp as a backup and just want it recordable and quiet ( as best it can) . Thanks for any help guys.
 

stark

Silver Supporting Member
Messages
3,392
I have the same problem. You just have to keep trying tubes in V1 slot until the hum is tolerable. I had a good GE 12ax7 that just started rattling and humming. I really like a 6072a in V1.
 

klbabcock11

Silver Supporting Member
Messages
308
i am hoping the 5751 i ordered will clean it up. I tried a spax7 from Mesa Boogie in v1 and it did nothing. those are supposed to be low noise
 

Soothsayer

Silver Supporting Member
Messages
4,665
I always twist the heater wires and route them away from the board along the outside of the chassis. Tubes as mentioned make or break the hiss issue, not just the preamp but the power tubes play a big part as well.
 

sled

Member
Messages
732
Sorry but your approach isn't much better than this...



You may get lucky, but then you won't know what the issue was because you did so many things. Maybe then it won't matter, unless it returns.

IMO, it's bench time or FS time.
 

klbabcock11

Silver Supporting Member
Messages
308
Sorry but your approach isn't much better than this...



You may get lucky, but then you won't know what the issue was because you did so many things. Maybe then it won't matter, unless it returns.

IMO, it's bench time or FS time.
Hahahahaha thanks ! I feel that way
 

TexGoneNW

Member
Messages
90
I have one of the earlier issues (tweed, with the blue frame alnico speaker).

You're gonna like that 5751. I got a couple of JAN GE 5751's a good while back, and they've served me well in the PJ. In that amp, that tube settled down the mild-to-wild a bit, in a useful way.
 

klbabcock11

Silver Supporting Member
Messages
308
So far ive knocked out about 75 percent of the hum with nbo mods here is what i did.

I installed jj 5751 in the pre a nos sovtek 12ax7 that it big fat and warm and a low gain matched jj/ruby el84s
I cut the wire bundle inside the chassis twisted the heater wires and re routed the wires carefully.
I then used some electronic cleaner on the cheapo volume and tone pots which i heard can cause some of the microphonic noise...
Presto brought all the hum and his down big time.
 

klbabcock11

Silver Supporting Member
Messages
308
next on the list is adjusting the bias so it doesn't run so hot, and dropping the gain a little, maybe adding a capacitor 47uf cap. Im sure that would get me pretty much in the clear
 

klbabcock11

Silver Supporting Member
Messages
308
Why not take all that money and time and buy an amp that doesn't have issues.
A common question...
Well I happen to have several high end amps and a very nice Reeves on the way. But i happen to like this amp personally, it takes pedals better than 85% of the current market amps and its a perfect small club amp when i cant use my 25 plus watt beasts.
 

klbabcock11

Silver Supporting Member
Messages
308
And money wise i didnt spend anything but 38 bucks on tubes and maybe 10 bucks on some new caps , bought the amp under 200 bucks and even with a new speaker im still about 25 bucks below map on the amp new
 

rhinocaster

Gold Supporting Member
Messages
23,728
I love the tone of the Pro Jr and spent a fair amount of time trying to tame the hum....re routed wires, wound the heater wires etc....

I finally took the advice the it was the V1 tube and started trying different tubes in that position. I finally plugged in a JJ ECC83 in there and the hum went away. I've used this tube in my last two Pro Jrs and I have no hum problems.

Bought several of these tubes...

Worked for me. :)
 






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