May need an amp tech

popthree · February 25th, 2005, 10:51 PM

I've been using an old silver face champ for the last few years. It was bone stock, speaker and all, til this last summer, at which time, I replaced the stock speaker with a mojotone. After only a couple of months, the mojotone blew out. I went out and bought an over the counter replacement...jensen reissue. sounds ok. but now I'm noticing a funny gravely sound in the amp...It's not the speaker..as I've put the original back in to compare and the sound is still there.
The sound is kinda quiet, and easy to overlook, but consistently present. When I play a clear note, as its ringing out I can hear this low, gravely sound...almost like something grinding. Is it a tube going bad?
Is something more serious wrong? What would cause the speaker to blow so quickly? ( I was playing close to dimed quite a bit) Possibly related?

marty1776 · February 25th, 2005, 11:48 PM

If you have a spare power tube, I'd swap them out and see what happens before you do much else.
Ryan

popthree · February 28th, 2005, 09:46 PM

well I ordered a set of JJ's. guess we'll see if its the power tube, or something worse.

4mal · March 1st, 2005, 02:38 PM

Filter cap's can do that as well if it is the sound I'm thinking of. I think of it as coffee percolating. Fortunately recapping a Champ can't be too very expensive. I'm just about to do my Pro Reverb which is just a little more involved and with pot cleaning I expect it will come home at about $100.

1612112 · March 1st, 2005, 05:55 PM

... transformer interleaving. If you've changed speakers and the replacement is not as well matched it could have caused the output transformer to warm up and loosen laminates especially on an older tranny which probably has no resin on it right? If this is the case it's an easy fix... get some good strong zip ties and run them through the vacant holes in the transformer laminates (where bolts were never put by cheap-ass tranny builders) crank the ties shut and see if it goes away. If it does replace those zip ties with bolts when you have time.
pjb

popthree · March 1st, 2005, 09:15 PM

I hope it is tubes...since I already have them on the way. amp should sound better even if that isn't the problem. thanks for the other tips.. if tubes don't do the trick I'll take it in and have it serviced.

popthree · March 2nd, 2005, 07:49 PM

well, it was tubes...replaced the 6v6 (with a JJ 6V6 )and the 12ax7 (with a JJ ECC83S) and no more weird noise... except for the ones I'm making with the guitar.

The amp seems a little louder and has retained the tone I expect.
thanks for the suggestions!

ps-Bob @ eurotubes was really helpful....and fast. I ordered them Sunday night...I received them today, Wednesday.

February 25th, 2005, 10:51 PM	#1 (permalink)
popthree Friend of Leo's Join Date: Jan 2005 Location: Tulsa Age: 43 Posts: 2,949 49 Photos	May need an amp tech I've been using an old silver face champ for the last few years. It was bone stock, speaker and all, til this last summer, at which time, I replaced the stock speaker with a mojotone. After only a couple of months, the mojotone blew out. I went out and bought an over the counter replacement...jensen reissue. sounds ok. but now I'm noticing a funny gravely sound in the amp...It's not the speaker..as I've put the original back in to compare and the sound is still there. The sound is kinda quiet, and easy to overlook, but consistently present. When I play a clear note, as its ringing out I can hear this low, gravely sound...almost like something grinding. Is it a tube going bad? Is something more serious wrong? What would cause the speaker to blow so quickly? ( I was playing close to dimed quite a bit) Possibly related? __________________ "chips are falling....." -Dr. Johnny Fever

February 25th, 2005, 11:48 PM	#2 (permalink)
marty1776 NEW MEMBER! Join Date: Feb 2005 Location: St. Charles, MO Posts: 7	do you have a spare power tube? If you have a spare power tube, I'd swap them out and see what happens before you do much else. Ryan

February 28th, 2005, 09:46 PM	#3 (permalink)
popthree Friend of Leo's Join Date: Jan 2005 Location: Tulsa Age: 43 Posts: 2,949 49 Photos	well I ordered a set of JJ's. guess we'll see if its the power tube, or something worse. __________________ "chips are falling....." -Dr. Johnny Fever

March 1st, 2005, 05:55 PM	#5 (permalink)
1612112 Tele-Meister Join Date: Nov 2004 Posts: 229	It could also be... ... transformer interleaving. If you've changed speakers and the replacement is not as well matched it could have caused the output transformer to warm up and loosen laminates especially on an older tranny which probably has no resin on it right? If this is the case it's an easy fix... get some good strong zip ties and run them through the vacant holes in the transformer laminates (where bolts were never put by cheap-ass tranny builders) crank the ties shut and see if it goes away. If it does replace those zip ties with bolts when you have time. pjb

March 1st, 2005, 09:15 PM	#6 (permalink)
popthree Friend of Leo's Join Date: Jan 2005 Location: Tulsa Age: 43 Posts: 2,949 49 Photos	I hope it is tubes...since I already have them on the way. amp should sound better even if that isn't the problem. thanks for the other tips.. if tubes don't do the trick I'll take it in and have it serviced. __________________ "chips are falling....." -Dr. Johnny Fever

March 1st, 2005, 02:38 PM	#4 (permalink)
4mal Friend of Leo's Join Date: Mar 2003 Location: The Gorge Posts: 2,198	Filter cap's can do that as well if it is the sound I'm thinking of. I think of it as coffee percolating. Fortunately recapping a Champ can't be too very expensive. I'm just about to do my Pro Reverb which is just a little more involved and with pot cleaning I expect it will come home at about $100.

March 2nd, 2005, 07:49 PM	#7 (permalink)
popthree Friend of Leo's Join Date: Jan 2005 Location: Tulsa Age: 43 Posts: 2,949 49 Photos	well, it was tubes...replaced the 6v6 (with a JJ 6V6 )and the 12ax7 (with a JJ ECC83S) and no more weird noise... except for the ones I'm making with the guitar. The amp seems a little louder and has retained the tone I expect. thanks for the suggestions! ps-Bob @ eurotubes was really helpful....and fast. I ordered them Sunday night...I received them today, Wednesday. __________________ "chips are falling....." -Dr. Johnny Fever