Blues Junior problem... volume fluctuations?

ruger9 · June 7th, 2008, 05:14 PM

I've got a 2006 NOS tweed Fender Blues Jr. 2xEL84. Bought used, Seems in perfect condition. Having volume fluctuation problems, thought it was a power tube. Replaced the power tubes, problem not fixed. Noticed the Fat switch, when I was having these volume fluctuations, didn't appear to be working right either. Hmm... is it possible the fat switch circuitry is turning itself on & off? At this point, all new tubes, problem remains intermittent. Somedays amp sounds perfect, other days volume fluctuations/fat switch not working properly.

Is it possible the fat switch may need to be "cleaned"?

Any suggestions greatly appreciated! Trying to figure this out myself before taking it to a tech.

eugenedunn · June 7th, 2008, 07:14 PM

Check the fat switch jack, which is right next to the 1/4-inch speaker output jack under the chassis. Is there anything plugged in there? Or possibly a short in that jack which is activating the FAT circuitry?

That's my guess, and I'm stickin' to it.

ruger9 · June 7th, 2008, 11:13 PM

I never thought of the fat switch JACK... I don't have the pedal, but it is entirely possible the jack might be dirty... especially if it's a switching jack. I know in the Peavey Classics, the effects loop jacks can get dirty if you don't use them regularly, and cause intermittment problems.

Good idea!

Billm · June 8th, 2008, 10:43 AM

The Fat switch and jack work by grounding a -15V signal. You'd have to have some foreign material in there like steel wool or something to cause a false ground. Anything's possible, but it's not too likely. If the internal connection on the jack is dirty or open, it takes the Fat switch out of the circuit and it doesn't work at all.

emu! · June 8th, 2008, 12:25 PM

Quote:

Originally Posted by ruger9

I've got a 2006 NOS tweed Fender Blues Jr. 2xEL84. Bought used, Seems in perfect condition. Having volume fluctuation problems, thought it was a power tube. Replaced the power tubes, problem not fixed. Noticed the Fat switch, when I was having these volume fluctuations, didn't appear to be working right either. Hmm... is it possible the fat switch circuitry is turning itself on & off? At this point, all new tubes, problem remains intermittent. Somedays amp sounds perfect, other days volume fluctuations/fat switch not working properly.

Is it possible the fat switch may need to be "cleaned"?

Any suggestions greatly appreciated! Trying to figure this out myself before taking it to a tech.

If it just does it on certain days, maybe it's dirty AC power in the building. Try it in another building when you get a chance. Also, make sure there are no ceiling fans turned on when you are playing, especially if it is in a small room. Ceiling fans will make the amp sound like it has tremolo.

June 7th, 2008, 05:14 PM	#1 (permalink)
ruger9 Tele-Afflicted Join Date: Dec 2004 Location: Hackettstown, NJ Posts: 1,726	Blues Junior problem... volume fluctuations? I've got a 2006 NOS tweed Fender Blues Jr. 2xEL84. Bought used, Seems in perfect condition. Having volume fluctuation problems, thought it was a power tube. Replaced the power tubes, problem not fixed. Noticed the Fat switch, when I was having these volume fluctuations, didn't appear to be working right either. Hmm... is it possible the fat switch circuitry is turning itself on & off? At this point, all new tubes, problem remains intermittent. Somedays amp sounds perfect, other days volume fluctuations/fat switch not working properly. Is it possible the fat switch may need to be "cleaned"? Any suggestions greatly appreciated! Trying to figure this out myself before taking it to a tech. __________________ "I've got callouses, from all those nights, spent playin' a Telecaster, 'till my fingers bled Bud Light" - Travis Tritt

June 7th, 2008, 11:13 PM	#3 (permalink)
ruger9 Tele-Afflicted Join Date: Dec 2004 Location: Hackettstown, NJ Posts: 1,726	I never thought of the fat switch JACK... I don't have the pedal, but it is entirely possible the jack might be dirty... especially if it's a switching jack. I know in the Peavey Classics, the effects loop jacks can get dirty if you don't use them regularly, and cause intermittment problems. Good idea! __________________ "I've got callouses, from all those nights, spent playin' a Telecaster, 'till my fingers bled Bud Light" - Travis Tritt

June 7th, 2008, 07:14 PM	#2 (permalink)
eugenedunn Tele-Holic Join Date: Dec 2006 Location: Sacramento, CA Age: 55 Posts: 839 37 Photos	Check the fat switch jack, which is right next to the 1/4-inch speaker output jack under the chassis. Is there anything plugged in there? Or possibly a short in that jack which is activating the FAT circuitry? That's my guess, and I'm stickin' to it.

June 8th, 2008, 10:43 AM	#4 (permalink)
Billm Tele-Holic Join Date: Mar 2008 Location: New Jersey Age: 62 Posts: 575 1 Photos	The Fat switch and jack work by grounding a -15V signal. You'd have to have some foreign material in there like steel wool or something to cause a false ground. Anything's possible, but it's not too likely. If the internal connection on the jack is dirty or open, it takes the Fat switch out of the circuit and it doesn't work at all.