Blues Junior Buzzing

[Alowhitep]

Hi

I'm new to this forum and also quite new to Tube amps, i have my BJ3 about a year now. I never had a problem with it but I haven't used it for a few weeks and when i plugged it in yesterday its got a very ugly buzzing/crackling noise. I haven't replaced any of the tubes yet but i did swap them around, V1 for V3 etc, it doesn't make a difference. I'm gonna try replacing all the tubes tonight but just thought I'd put up a post here and see if anyone had any advice first.

Heres a few observations I've made on the problem.

1. The buzzing really only kicks in once i insert a jack, its doesn't matter if the Jack is connected to a guitar or not though obviously it changes the nature of the buzzing if it does.

2. When i hold the guitar the buzzing is much worse than if its on the stand.

3. When i play the buzzing goes away

4. With the volume and master down the buzzing goes away and it really only kicks in when turned up to 4/5 or beyond.

5. Turning down the Treble to zero almost completely eradicates the buzzing even at full volume, turning down the Mid reduces it and turning down the Bass or Reverb has no effect

6. Its slightly worse with Fat on.

7. My guitar probably needs the pots and jack input cleaned as fiddling with these can have an effect on the buzzing but i don't think this is the problem as the same buzzing is there when i tried a keyboard through the amp.


Any advice would be great guys cheers

[52 Bill]

Welcome to the place.

1. The buzzing really only kicks in once i insert a jack, its doesn't matter if the Jack is connected to a guitar or not though obviously it changes the nature of the buzzing if it does.

Try this test. Plug your cord into the jack and with the amp on, touch the tip of the free end to the metal chassis. Is the amp just as quiet as it is with no cord plugged into the jack?

[Alowhitep]

Hi and thank you

That's interesting. Ok I'm not sure what you mean the metal chassis but I tried touching the tip of the free end off a few metal parts on the amp.

First I tried the bolt on the input jack so basically just back to where the jack was coming out, this had no effect.

Then the on off switch and Jewell light casing, this reduced the noise a lot.

I tried the screws around the handle and this made it louder.

I tried the grill that protects the tubes and this made it really crackle and hum loudly.

The one thing that really reduced the noise dramatically, almost down to what it's like without the jack plugged in, was the screw on the topside just beside the jack input.

Any idea what that could mean because I'm completely stumped.

[TimmyP1955]

Does the gain seem normal (IOW is it the correct volume when all the controls are set your usual way?). Could be a loose ground connection, bad preamp tube (heater hum or power supply ripple getting into the audio) , or a bad bypass cap on V1B (not likely if the gain is normal).

[Alowhitep]

Yeah the gain seems pretty normal. In actual fact the amp performs pretty normally once I start playing its only when I stop that the buzzing is there. Now I know tube amps are going to have a certain amount of buzz or hum but this is very excessive. I'd be inclined to think its the preamp tube but switching them around has had no effect. In any case I'm gonna try replacing the tubes. Not sure what the bypass cap Is but I'll research that thanks.

[g1]

How about when you turn off the volume on the guitar?
52Bill's test may have been to see if the noise is being picked up outside of the amp. Have you tried it at other locations?

[Justin Thomas]

What's the guitar? Based on numbers 1,2,4, & 5 above, I nominate room "noise." Remove the cable from the input jack of the amp and set the knobs where you usually play. Does it still buzz? Crank the knobs on 10. Still? Remember, a tiny bit of buzz and/or a slight amount of hiss is normal with the knobs cranked.

The buzz happening when you have the guitar on versus in the stand could be coincidence - the electromagnetic noise being picked up by the pickups mat be bucked because of position.

You say the buzz goes away when you play. Does it go away, or is it drowned out?

I have all of the exact same problems and solutuons in the house where I just moved. The house is full of 20 people's phone chargers, computers, a big giant furnace right under the jam room, in a decent-sized city, etc. If I hold my guitar at exactly ONE particular angle, a very impractical one, the heinous buzz goes 90% away. Move 5° in ant direction, BUZZZZZZZ...

Got a humbucker-equipped guitar? I think your room is "noisy" as all get-out.

Justin

[Alowhitep]

Ok so the guitar i have is a Strat, Mexican but with American pickups, (single coil) and i replaced the pots. I've tried it in several rooms in my own house and brought it to a friends house and played his almost brand new Special Series Strat HSS, (its got a humbucker) through it. Location made no difference, with his guitar the noise was a little less angry and when switched to the humbucker better again but still quite bad.

Justin Tomas yeah when i take the cable out and have it set to my usual preferences there is virtually no noise, as you say just the normal hiss you get from any amp. When i crank everything to max the hiss obviously increases but again its just what you would expect from a properly functioning amp.

When i play the the noise almost completely goes away its not just disguised its actually clean. One way i could describe it is its like a radio where you can't tune the station properly and its got a lot of white noise but when you touch the antennae the signal becomes clear. (odd description i know).

I've played this amp in dozens of busy venues without issue, the room its in now is my mothers house which is fairly secluded and theres not much around that i think could be interfering.

[Alowhitep]

Not with the guitar or amp today so i can't try this out but im pretty sure that yes turning down the volume on the guitar cuts out the noise

[52 Bill]

If the amp is fairly silent with no cord plugged into the jack, then it would suggest that the noise is related to the cord or the guitar. Unless you are not describing the sound in a way that we can all understand.

Have you tried other cords?

[Chuck H]

I might try cleaning the amps input jacks. Can we assume that when you took the amp to your friends house that you used a different cord too? That amp has a standard type input circuit. I mention this because some modern amps have input jack switches that could affect other amp circuits, but yours doesn't. So if the amp behaves with nothing plugged in that would limit the problem to the jack, it's wiring/board pads and traces or the first gain stage triode or it's solder connections, board pads or traces. The tube possibility is less likely, but perhaps it behaves better when the grid is grounded. Which happens when you turn your guitar to zero or unplug the cord from the input.

Oxides could have formed on the jack, tube socket holes and/or tube pins in the last few weeks that you haven't played.

[Alowhitep]

If the amp is fairly silent with no cord plugged into the jack, then it would suggest that the noise is related to the cord or the guitar. Unless you are not describing the sound in a way that we can all understand.

Have you tried other cords?

Thanks Bill i'm sorry but I've described it as best i can. As i said I'm quite new to tube amps and actually I've only been plugged in a few years so I'm not quite up to speed with the terms you guys might use to describe problems. Anyway yes as i said i tried it out through a friends guitar which is pristine so I'm sure its not a guitar issue, also yes I've tried it with a lot of different chords and also tested those cords through other amps to make sure they work ok.

[Alowhitep]

I might try cleaning the amps input jacks. Can we assume that when you took the amp to your friends house that you used a different cord too? That amp has a standard type input circuit. I mention this because some modern amps have input jack switches that could affect other amp circuits, but yours doesn't. So if the amp behaves with nothing plugged in that would limit the problem to the jack, it's wiring/board pads and traces or the first gain stage triode or it's solder connections, board pads or traces. The tube possibility is less likely, but perhaps it behaves better when the grid is grounded. Which happens when you turn your guitar to zero or unplug the cord from the input.

Oxides could have formed on the jack, tube socket holes and/or tube pins in the last few weeks that you haven't played.

Thanks for the reply, Yeah i have tried with several chords and also tested the chords through other amps to make sure they're ok. I cleaned all the jack inputs with a contact cleaner and also the tube inputs, it made no difference that i can see... i picked up some new tubes today so hopefully that helps If not then yeah its probably something to do with the wiring/board pads or traces and probably best i consult a pro at that stage.

[Alowhitep]

cords not chords obviously...sorry

[Alowhitep]

I replaced the V1 preamp and largely this seems to have fixed the problem. The buzzing has reduced dramatically, I'll proabaly go ahead and relplace all the tubes to see if it cleans it up some more but its about 90% of the way there so im happy enough. My guitar certainly needs some attention as it is still causing a lot dirt in the sound. I put two semi acoustic's trough the amp and they're coming through almost completely clean so that has me pretty satisfied that the amp itself is more or less sorted now.

Thanks for the time and advice guys.

Al