SF Vibro Champ fuzz

[rokplo]

Hi !

My 70's silverface vibro champ is fuzzing with lower notes : it's not very loud, but i clearly hear it, and if i let the note last longer, i only hear the fuzz sound .... i tried to change the valves (i put back the old ones, that still worked fine) with no change - also tried with another guitar - the speaker is new (jensen)

may i have a look at the caps ? another idea ?


thanks a lot !!!

[kor]

Hi !

My 70's silverface vibro champ is fuzzing with lower notes : it's not very loud, but i clearly hear it, and if i let the note last longer, i only hear the fuzz sound .... i tried to change the valves (i put back the old ones, that still worked fine) with no change - also tried with another guitar - the speaker is new (jensen)

may i have a look at the caps ? another idea ?


thanks a lot !!!

According to what you have posted, I don't like to guess unless I have the amplifier right in front of me, but even though the speaker is new, try another one just to eliminate that problem. I could quote twenty other problems, but like to stick to one at a time.

[Enzo]

I would also consider the speaker. Did it make this noise before you changed the speaker? Try connecting the amp to a different speaker.

Just because it is new doesn't mean it can't have a defect.

[Dave Curtis, dB AudioTech]

If the new speaker's mounting nuts are too tight, it can warp the frame. That can make the voice coil rub and cause a sound like the one described.

[rokplo]

The speaker is new, but i plyed one year without a problem ;-)

When i say "new", i just mean it"s not the original one ....


the sound is really like an electronic fuzz (like a pedal effect) ... any suggestion ?

[slidincharlie (Carlo P)]

The fuzzy buzz in my ex-VibroChamp was caused by the speaker.
Not that in your case this has to be the culprit...

[rokplo]

it really doesn't sound like a speker buzz for me ... i tried playing while touching the paper of the speker, and the fuzz was still there ...

it sounds "electronic" really like a pedal effect - it's near the "seven nation army" sound (but of course not as loud - just a little bit in the background)

[rokplo]

i took out the amp from the cab and tried to move the caps/wires inside with no result. With the amp out of the cabinet, the fuzz is still here.

The board has bulged in the middle, and has a big wave - maybe the board material has become conductive ??? not sure that theese 70's boards could have such problems ?

I think i'll try to heat all the solder points on the board to avoid cold solders ?

any other suggestions ?


Thanx !!!!!!

[rokplo]

I heated all the solder points on the eyelet board with some new solder .... and no result, this fuzz is still here ....


Help !!!!!!!! i need some experts advices ;-))

[Jag]

Try a different speaker and see what happens.

[rokplo]

i 've taken the speaker out of the box to examine it : it's perfect, the cone shows no default or scratch - it's new, less than one year, and always sound perfectly .... so i don't understand why it could suddenly fuzz ... the fuzz sound is there, whatever the voume level is - it just grows up with the volume.

I don't actually have another 4 ohm speaker to make a test ... i could eventually try with a 12' 8 ohm speaker .... is it dangerous for the output tranny ?

[hollisdevillo]

no, just as long as it's not a lower impedance speaker. try it with the 8 ohm.

[Mandopicker]

Have you changed the tubes to "KNOWN" good tubes?

[rokplo]

for the preamp tubes, yes . For the power and rectifier tubes, i used the old tubes that were in the amp when i bought it. There were no fuzz at that time. When i changed the tubes, i had EXACTLY the same fuzz sound ...

[slidincharlie (Carlo P)]

You should *definitely* try a different speaker (the 8 ohm will do) before chasing the buzz elsewhere...