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Pro Jr. / hum

3/15/2000 2:55 AM
joe Z
Pro Jr. / hum
I just picked up a used pro jr. for $145. Very neat little amp. Although it is very quiet when nothing is inserted into the input jack, it does begin to buzz when anything is plugged in, even just a cord by itself. I don't believe it's the tubes, but rather something at the input jack. Am I on the right track. Any opinions? Joe
3/15/2000 5:52 AM

I've replaced the input jack on quite a few of these because of hums.  
I got to the point where I'd use a common Swichcraft shorting jack and a seperate wire to the other side of the board.  
Also the filament supply's 47 ohm virtual center tap resistors went bad a few and needed replacements.  
With no way to adjust or balance the idle current, (with out a minor mod with a small trim pot), an old and unbalanced power tube set can hum pretty good in these too.  
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3/15/2000 3:54 PM
joe Z

Muchos Gracias Bruce. It was an impulse buy, but one that will I actually won't regret. Joe
3/17/2000 9:42 PM

You know why they hum...  
They don't know the words
3/17/2000 11:10 PM
John S.

Great amp indeed Joe...I own both a blonde one and a tweed one.....When you get her up and running right,try some n.o.s. Phillips EL84's in there and some good preamp tubes(THE 12ax7 LPS Sovteks are pretty good sounding preamp tubes today....The Sovtek EL84's that are probably in your amp now are pretty good sounding also,but the Phillips make the amp a bit headroomier,louder,and fuller sounding to my ears anyway....If you like the quick breakup of the Sovtek tubes....Go with it Joe! John S.
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