'59 Bassman Reissue noise

[Flyboy]

Recently acquired and quite happy with it. This is my second Bassman, the '59 Reissue, opposed to my first one, which was the LTD. This one has an aftermarket mod, in that there is a Master Volume pot fitted where the Ground switch is on the Reissue.

The problem is an intermittent noise, like a combination of rustling wind with an occasional fizzling. It exhibited this the day I got it but it then disappeared. Now it's back.

One thing I noticed this time was that I turned both channel volumes off, leaving the Master up around 75% and the noise was still there. Backing off the Master reduced the rustling a bit but turning it up made it worse.

Any ideas? I'll pull the chassis later and take a photo of the Master wiring path.

 

[Apache49]

Sounds like a tube has gone microphonic. Tap each tube gently with a piece of plastic to see if you can replicate it. Otherwise replace each ax7’s one at a time.

 

[dan40]

Yep...try a fresh tube in each position, one at a time. This will allow you to narrow it down to the exact tube that may be causing an issue. Cleaning the tube pins is also wise when issues like this pop up. If neither of these two suggestions help, it could be a bad resistor that will take a bit of troubleshooting to find.

 

[nathan5782]

I had a similar issue with a '67 Bandmaster. I replaced a few resistors that were a little out of spec and tried some different preamp tubes that were micro phonic. The problem still happened until I eventually tried new power tubes/valves.

 

[Paul G.]

I'd start with the tubes.

 

[Sea Devil]

Sounds like a power tube with slight vacuum loss, but it might be poor contact in the socket. It doesn't sound like a pre-amp tube issue.

 

[BlueTele]

Recently acquired and quite happy with it. This is my second Bassman, the '59 Reissue, opposed to my first one, which was the LTD. This one has an aftermarket mod, in that there is a Master Volume pot fitted where the Ground switch is on the Reissue.

The problem is an intermittent noise, like a combination of rustling wind with an occasional fizzling. It exhibited this the day I got it but it then disappeared. Now it's back.

One thing I noticed this time was that I turned both channel volumes off, leaving the Master up around 75% and the noise was still there. Backing off the Master reduced the rustling a bit but turning it up made it worse.

Any ideas? I'll pull the chassis later and take a photo of the Master wiring path.

Buy some rubber rings to put around each preamp and power tube. You are getting oscillation from somewhere. The rings are a cheap way to "rule-out" oscillation as well. If you have the ringing/vibration thing happening "with" the rubber rings ion each tube, then it is a circuit problem, or a "screw/washer/nut" issue. So, check and tighten-up each little screw and washer in the amp including the chassis mounting screws. You might have one - or more - that are oh so slightly loose, and they are vibrating as you play, especially washers. Same for the speaker mounting screws. Tighten them up. And...while not likely a source, tighten up the screws that mount the amp's four rubber or metallic feet to the cabinet. If you are playing on a non-carpeted hardwood or laminate floor, try putting the amp on a carpeted surface. You can buy a cheap bathroom rug that is 18" x 24" or 24" x 30", set the amp on it, and if the vibration goes away, you're good to go. Good luck.

 

[Flyboy]

Yep...try a fresh tube in each position, one at a time. This will allow you to narrow it down to the exact tube that may be causing an issue. Cleaning the tube pins is also wise when issues like this pop up. If neither of these two suggestions help, it could be a bad resistor that will take a bit of troubleshooting to find.

Yeh, a load resistor did come to mind. V1 was swapped out for a 12AY7 so I know it isn't that one.

Thanks to all for input and I'll take on board suggestions.

 

[Axis29]

Don't discount that 12ay7. Even new tubes can come up noisy. Sadly, even if the tube is quiet in a different amp, it can still be noisy in yours....

My 5e3 is very sensitive to noisy tubes.... I can put them in other amps and use them for years.... They can sound fantastic in other amps, until I plug them into my 5e3.

But, I agree, if not a tube... probably a resistor.


And, congrats on the new Bassman!

 

[dan40]

Yeh, a load resistor did come to mind. V1 was swapped out for a 12AY7 so I know it isn't that one.

I would look at the rectifier and power tubes. I have had a bad rectifier produce some wind like noises in an amp before. Tube pins can also cause noise like this. Pulling them and reinserting several times will help to clean any oxidation from the pin's surface.

 

[Sea Devil]

I could not disagree more with all of BlueTele's suggestions. I think there's absolutely zero chance that that type of noise could come from oscillation or mechanical vibration. None.

I also think there's no way in hell that it could be coming from the rectifier. A resistor or two? Maybe, but not super-likely. I stand by my earlier post.

 

[Flyboy]

Don't discount that 12ay7. Even new tubes can come up noisy. Sadly, even if the tube is quiet in a different amp, it can still be noisy in yours....

My 5e3 is very sensitive to noisy tubes.... I can put them in other amps and use them for years.... They can sound fantastic in other amps, until I plug them into my 5e3.

But, I agree, if not a tube... probably a resistor.


And, congrats on the new Bassman!

You know what? You were right! It's noisy when tapped; all other valves pass the tap test, even the original 12AX7.

The rustling is still there and I'm convinced it's got something to do with the V1 socket because tapping that increases the rustling, albeit intermittently.

 

[Axis29]

You know what? You were right! It's noisy when tapped; all other valves pass the tap test, even the original 12AX7.

The rustling is still there and I'm convinced it's got something to do with the V1 socket because tapping that increases the rustling, albeit intermittently.

Well, Not to really confuse things... But V1 is usually the noisiest tube when you tap on it. But, I bet you've narrowed the issue down to the location in the circuit. Might try another 12ay7? Might also be some other component nearby?

 

[Flyboy]

Well, Not to really confuse things... But V1 is usually the noisiest tube when you tap on it. But, I bet you've narrowed the issue down to the location in the circuit. Might try another 12ay7? Might also be some other component nearby?

I don't get it, because the 12 AY7 is a lower gain valve; it shouldn't be that noisy when tapped?

 

[2L man]

I don't get it, because the 12 AY7 is a lower gain valve; it shouldn't be that noisy when tapped?

Usind limited amount of data you just must assume that it is few db less microphonic because its gain is few db lower!

 

[schmee]

sounds like a pre tube ....."rustling wind"

 

[Axis29]

I don't get it, because the 12 AY7 is a lower gain valve; it shouldn't be that noisy when tapped?

It's the first step down the gain stage highway. Any noise created there gets amplified over and over again.

 

[Flyboy]

So, I'm back with this problem again. It's now back, after me replacing V1.

The Bassman hasn't been my main amp for a couple of years, and since I moved it to replace V1, I was lulled into a false sense of security with the issue being sorted.

Have a look at this photo. The pin sockets that feed blue wires 1 and 2 are noisy when tapped, and have a lot of wiggle. The socket for number 3 (green) makes noise as well, but nothing like 1 or 2; 2 is the loudest. The valve itself is firm in the socket.

Tapping any other valve, or raking wooden stick over any other valve contact makes no noise. Yet if V1 volume is down, and V2 is up a bit, that's the channel that makes the noise. I know these two channels interact with each other, but the V1 socket is surely at fault here.

Tagging @Peegoo

 

[elpico]

I have to disagree with the earlier suggestion that tapping on things is the way to sort your issue. That some tubes have a louder response to tapping than others is 100% expected and normal due to the way these circuits work. It doesn't necesarily tell you there's a problem there.

In your first post you said the problem still occurs with the channel volumes down and that strongly suggests V1 is not making the sound you're hearing. V1 comes before the volume controls so turning them down basically eliminates any sounds V1 makes from the circuit. It's not *impossible* for it to still cause a problem with the volume down, but it's very unlikely to be the issue.

The suggestion to pull tubes in order, v1, v2, then v3 is a better way to isolate this than tapping.

 

[Flyboy]

I have to disagree with the earlier suggestion that tapping on things is the way to sort your issue. That some tubes have a louder response to tapping than others is 100% expected and normal due to the way these circuits work. It doesn't necesarily tell you there's a problem there.

In your first post you said the problem still occurs with the channel volumes down and that strongly suggests V1 is not making the sound you're hearing. V1 comes before the volume controls so turning them down basically eliminates any sounds V1 makes from the circuit. It's not *impossible* for it to still cause a problem with the volume down, but it's very unlikely to be the issue.

The suggestion to pull tubes in order, v1, v2, then v3 is a better way to isolate this than tapping.

That's how I remembered it then. Now, it's only doing it with the Bright channel turned up. I've just turned it on again... and nothing, just amp hiss. I put a jumper back in from Normal 1 to Bright 2 and it came back, briefly. Now it's gone again.

I give up with this thing.


Addition: even tapping both housings of the jumper results in a buzzing noise. These housings are plastic; why would this happen?