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#1
I've been noticing that my low E string seemed to buzz above about the 8th fret. I thought it was string height adjustment.

Today I got a couple of new preamp tubes and wanted to compare the sounds. I heard the buzzing on the low E string. I also heard it on the A and D strings. I adjusted the strings higher. The buzzing was still there. I tried a different guitar. Same buzz.

I thought it might be a speaker, so I fretted the E string around the 8th fret and touched the cone of each speaker as I hit the note. Still buzzed. (This is a Fender Super Reverb Reissue with 4 speakers).

I have an attenuator connected between the amp and speakers, so I took that out of the loop. I still got buzzing.

I traded out preamp tubes. No change. I swapped out power tubes. Still no change.

The buzzing doesn't start until the volume knob is above three or so. It's not the loudness of the amp, because I can put the attenuator in the circuit to reduce the volume, and I'll still get the buzzing if the volume knob on either channel is above 3.

So, it doesn't seem to be something physical, as the actual volume of the amp doesn't make a difference. It's not the guitar, power tubes or preamp tubes. It's only when the volume in either channel is set to higher than 3.

I adjusted the bias the other day on the original tubes (which I'll put back in) and they were at 30-32.

Any suggestions?

Thanks for any replies.
#2
I should add that I discovered that if I played on the lower three or four open strings as chords, and hit them hard, that the sound from the amp is really brittle. This is with the volume setting at 5 or 6. If I kept hitting them hard, it would get even more brittle. At one point I lost almost all volume.
#3
Sounds like you've got bad filter capacitors or a power tube going out. My 60's Fender Champ does something similar and it's definitely the filter caps on it
Endorsed by Dean Guitars 07-10
2003 Gibson Flying V w/ Moon Inlay
2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
1989 Peavey VTM60

[thread="1166208"]Gibsons Historic Designs[/thread]
Last edited by Flux'D at Jan 9, 2014,
#4
Thanks, Flux'D. I tried new power tubes, but that didn't do it.

If I play the low E and A strings together, I get extremely heavy distortion to the point where it's almost garbled. The bass is really, really heavy, too.
Last edited by Monkeyleg at Jan 9, 2014,
#6
I checked the bias, and the tubes are at 32 and 34. The neck relief is fine. I tried 3 different guitars on the amp, and all do the same thing.

I cleaned the tube sockets, although I knew it was unlikely that was the problem. I looked inside the chassis for anything obviously wrong.

There's also a hum, and it gets louder as the volume knob is turned up. I've read that hums that get louder with volume change means it's preamp side rather than power side.

I really hate to spend the money on a tech if it's something I can figure out myself. I just have no idea where to start. Also, I don't know who a reputable tech in this area would be.
#7
I'd bet money it's the filter capacitors then. Whenever you dig into the guitar and push the tubes harder they require more juice, but the filter caps can't charge fast enough to supply them with adequate power on demand. Drop in power = outrageously nasty and weak, farty distortion.

Now that you mention there's excessive hum in the amp, it's pretty much a sure fire sign of bad filter caps.

EDIT: How old is the amp?
Endorsed by Dean Guitars 07-10
2003 Gibson Flying V w/ Moon Inlay
2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
1989 Peavey VTM60

[thread="1166208"]Gibsons Historic Designs[/thread]
#9
Flux'D, I don't know the age of the amp, but it's a '65 Reissue. Maybe I could find out the age from Fender using the serial number. It's in perfect shape.

The high notes don't seem to be affected, or affected enough for me to hear anything at room volume. The low notes (E, A, D strings) have a lot of buzz and noise, and a chord played with any two or three of those sounds garbled.

The guitars all have a lot more bass with this amp than they did before, and I haven't changed any controls.

I wonder how many capacitors there are in the preamp section that might contribute to this? Maybe replacing them all would be less expensive than paying a tech.
#10
Quote by Flux'D
I'd bet money it's the filter capacitors then. Whenever you dig into the guitar and push the tubes harder they require more juice, but the filter caps can't charge fast enough to supply them with adequate power on demand. Drop in power = outrageously nasty and weak, farty distortion.

Now that you mention there's excessive hum in the amp, it's pretty much a sure fire sign of bad filter caps.

EDIT: How old is the amp?



The hum is a dead give away to bad filter caps.

You should replace them all.

The amp itself may not be that old, but who knows how long those caps were sitting in a box at the Fender factory?
And electronic parts can come right from the manufacturer and be faulty.

If you replace them, MAKE SURE YOU DRAIN THE VOLTAGE FIRST.
Unless you want to end up in a pine box.

Edit:
And I'm just gonna take a wild guess, and without looking at the schematic, but there are probably 4 filter caps.
Last edited by CodeMonk at Jan 10, 2014,
#12
There is a simple way to identify faulty filter caps - measure the frequency of the hum. If it's 100Hz (120 in the US) then it is usually filter caps. If you have an android phone, install gstrings, it reads off frequency, not just note.

However, before getting radical - have you checked the screws holding in the speakers? Sounds to me like you are describing rattling. Look for loose scerws.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#13
However, before getting radical - have you checked the screws holding in the speakers? Sounds to me like you are describing rattling. Look for loose scerws.


Yes. I also disconnected the left pair to see if either of them was making the noise, then switched the wiring so I could disconnect the right pair. It's not the speakers.

Is there any reason why I should leave the job of replacing the caps to a tech, other than having to drain down the voltage from them? From looking in the filter cap box, it looks straightforward.
#14
As long as you drain the caps it's a pretty straightforward job - however, pay careful attention to polarity.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#16
Cathbard, is that 120 hz with a guitar plugged in? (Always told to not have a guitar plugged in).

If I have a guitar plugged in, but 10 or more feet away, it's making a 120 hz hum. After maybe 20 minutes at full volume, it starts generating a much louder hum, but at a different frequency.
#17
There's a hum.

I've decided to replace the capacitors. It's not that expensive. I figured I should replace the resistors on that board, too, just in case.

Any idea what wattage the resistors should be? Every schematic for that amp that I find has letters that are impossible to read.

Never mind. Found them. one 1W 4.7K flame proof, one 1W 1K flame proof, and two 1/2W 220K carbon film.
Last edited by Monkeyleg at Jan 11, 2014,
#18
It's hard for 120Hz hum to be coming from anywhere else but the power supply. What is this other frequency of which you speak?
Overall though, it sounds like a faulty earth.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#19
With the volume off, I can hear a faint hum from the speakers. As the volume is turned up, the hum gets louder. I compared the hum to tone generators on some internet sites that have different frequency tones, and it's 120 hz.

I tried playing through a song last night, and when I played notes on the low end of the fret board on the E, A and sometimes D strings, they weren't crisp even on the clean channel, but very distorted. The harder I hit the notes, the more distorted they became, to the point of being almost garbled. If I continue to hit these low notes hard, the sound will eventually cut out and I turn the amp off.

The capacitors and resistors for the cap board will run about $30. Then there's my time. If I luck out and that's the problem, it's a lot cheaper than taking it to a tech.

There's no Fender certified tech in my area. There's a guy that Guitar Center recommends, but I always take those recommendations with a grain of salt. In an area like mine, retailers sometimes recommend a repair guy because he's the only repair guy in the area.

This is the first time a bad ground was suggested. Any ideas as to where that might be?

I wish one of the parts had been leaking or showed obvious signs of failure.
#20
You just described the exact same thing my 1964 Champ does, and I guarantee it's the filter caps.
Endorsed by Dean Guitars 07-10
2003 Gibson Flying V w/ Moon Inlay
2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
1989 Peavey VTM60

[thread="1166208"]Gibsons Historic Designs[/thread]
#21
It does sound like filter caps. If it's the earth, it could be the coupling cap, if Fender are doing it the way they used to. They used to use a small cap between neutral and ground on the primary side of the power transformer, sometimes they'd blow. However, that would cause 60Hz Hum. For it to be 120Hz hum and earth you are looking at the joints between the filter caps and earth.
It could be both and replacing the caps would fix both. What I'd do is replace the caps and inspect all the solder joints while I was in there poking around with a soldering iron in hand.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#22
One last question (I hope). When I opened the cap box I found what looks to be silicone caulk between the capacitors. I've never seen that before. Does anyone know the purpose of this?
#23
Quote by Monkeyleg
One last question (I hope). When I opened the cap box I found what looks to be silicone caulk between the capacitors. I've never seen that before. Does anyone know the purpose of this?


Those caps have some weight to them.
Just keeps them stable during shipment and other movement.
#24
I replaced all five capacitors and checked the resistors, but it's still doing the same thing. I drained down the capacitors after checking the sound, and checked the voltage on them. I thought it was odd that the second of two 350 volt 100uf capacitors had roughly half the voltage of the other 350v 100uf and the three 500v 22uf (they were all the same). I drained them, then powered the amp on to try other things, then drained them again, and the same capacitor was about half the voltage.

I don't know what else to try. I adjusted bias up and down, but that didn't have any effect. I swapped out tubes again. Just to absolutely rule out speakers, I connected the Super Reverb speakers to my Peavey 30, and they sounded fine.

The power transformer hums a bit, but not loud. I have to get my ear near it to hear. One of the power tubes makes a noise through the speakers if I touch it. The other one doesn't.

I just hate to give a tech $200 or $300. If anyone else has a suggestion, I'd love to hear it.
#26
I can check it, if possible. I suppose beyond that all I can do is tap on connections with a pencil and maybe spray some things with freon.

Why couldn't it be my little $45 used bedroom practice amp? I'd just put it away in the closet and hope it would fix itself.
#27
Replace the power tubes.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#28
^ I think he's done that already.


Quote by Monkeyleg
I can check it, if possible. I suppose beyond that all I can do is tap on connections with a pencil and maybe spray some things with freon.

That's what I would do.

Not sure I would spray anything with freon. I was thinking contact cleaner like Dioxit but it sounds like you've done that already.

Also, have you tried a different guitar in your amp (sorry if you already said)*runs to check*
Last edited by 311ZOSOVHJH at Jan 18, 2014,
#29
It shouldn't be making any noise when he touches it. It is possible to get dodgey tubes from the factory. Happened to me not that long ago.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#31
I've swapped out everything: speakers, all tubes, cables, you name it. I've now replaced the filter capacitors. The only things left to replace are the transformers and components on the board.

The distortion doesn't start until the volume knob on either channel is over 3 or so. Up to that point, the sound is very clean. I don't know what that means, though.

I bought this used from the Guitar Center in Mansfield, TX and had it shipped to the store near me. The person I spoke to at the store said maybe Fender would honor the five year warranty even though there's no papers for it. I somehow doubt that.
#32
Tell me something. When you touch this tube and it makes a noise - does it move? See what happens if you give it a tiny, tiny wiggle.
Could be the tube socket. Have you cleaned them?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#33
Quote by Monkeyleg

I bought this used from the Guitar Center in Mansfield, TX and had it shipped to the store near me. The person I spoke to at the store said maybe Fender would honor the five year warranty even though there's no papers for it. I somehow doubt that.


Wait....is this a Reissue?


Have you swapped guitars completely yet?


and cleaned the sockets?


and tap tested?


tried rig at a different house?

stuff


free bump
#34
Cleaned all tube sockets, and tightened the pin sockets. One tube was a tiny bit loose, but I tightened the pin sockets for it and it's tight. The one that makes a noise doesn't even require me to move it. Just touching the glass makes a very quiet noise.

Wait....is this a Reissue?


Have you swapped guitars completely yet?


and cleaned the sockets?


and tap tested?


tried rig at a different house?

stuff


Tried 3 different guitars, all do the same. Tap tested. Haven't tried a different house.
#35
Quote by Monkeyleg
. The one that makes a noise doesn't even require me to move it. Just touching the glass makes a very quiet noise.

I'd replace that. Maybe microphonic.


http://s545.photobucket.com/user/buckethead_311/media/Amp%20stuff/Microphonicpreamptube.mp4.html
#36
Quote by Monkeyleg
Cleaned all tube sockets, and tightened the pin sockets. One tube was a tiny bit loose, but I tightened the pin sockets for it and it's tight. The one that makes a noise doesn't even require me to move it. Just touching the glass makes a very quiet noise.
It's ****ed.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#37
I'd replace that. Maybe microphonic.


I tapped on it lightly with a pencil and it made no sound.

I tried brand new power tubes and that didn't make a difference. The tubes that were in there (and are back in there now) sounded fine before all this.
#38
How are your screen resistors?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#40
How long have you had the amp? If it's still under Guitar Center's used warranty I'd take it back
Endorsed by Dean Guitars 07-10
2003 Gibson Flying V w/ Moon Inlay
2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
1989 Peavey VTM60

[thread="1166208"]Gibsons Historic Designs[/thread]
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