Amp Rattle

[Clive Hugh]

Can anyone point me in the right direction, I have a rattle in my amp - Fender "The Twin" - it carried on after I played a chord, I initially thouight it might be a loose power tube but they are all in as far as they will go.
I left the amp on for a while, about 5 minutes most elapsed and the sound went, so from this I am assuming it is in the tubes and goes when they get hot.
I have a gig next Saturday and can't get my amp to a repair shop and back before then as I live over 1100 miles from the repair shop.
So has anyone got any clues as to where I start looking or a simple fix?
Thanks
Clive

 

[Hard2Hear]

In my experience, Twins have a bad habit of shaking themselves apart. 100 watts in a combo is just alot to be going on in a small box.

Ive had a couple amps get a strange high pitched rattle, annd Ive (luckily) always been able to fix it by changing tubes. Sometimes the tubes themselves will come loose internally a bit and start making a rattling noise. If you can track it to a specific area, that will make it easier for you.

H2H

 

[Outlaws]

I have found when tubes are starting to go bad, the filiments inside them becoe loose and will produce an audible 'rattle'. Pull them out and shake them right next to your ear. If you can hear anythingdancing around inside, its time for new tubes.

But then it could be something else completely.

 

[-=¤willhaven¤=-]

Make sure the tubes are cool before you take them out and do any shaking though.

Personally I would turn the amp on, wait for it to rattle, then I would lightly tap each tube with a pencil. If your output tubes have one that sounds way different when tapped, it is probably microphonic. If you tap the preamp tubes, some are bound to sound different.

You usually get a "plink plink" or a "doonk doonk" sound when tapping tubes. If you get a "bwaaaaaaaaaaaaaaaaaaahhhhhhhhhhhnnnnnnnnnnnnnggggggg" ringing sound, that tube is most likely microphonic.

With the 12ax7 preamp tubes, if you suspect one of being microphonic, you can swap a pair of 12ax7s around to see if the microphonic tube still causes problems in the other slot. It should make it pretty obvious by swapping the tubes if the ringing sound follows the tube or if it is tied to that particular tube socket.

Sometimes a preamp tube that causes problems in one socket won't be an issue in another socket. But, I would just be safe and get rid of a noisy tube. Tubes aren't THAT expensive unless you're buying NOS American stuff. Even then, how often are you changing tubes?

And regardless, if you have a rattle, I would make sure that everything is secured on your amp. Go on a screw tightening spree everywhere. Tighten speakers, transformers, chassis, anything you can.

 

[Clive Hugh]

Thanks guys,

I'm going to let it warm up before the gig and not switch it off till after it's finished and then I'll send it away. I don't trust my hearing to go tapping the tubes, so I'll leave it to someone else.
Clive

 

[Outlaws]

Thanks guys,

I'm going to let it warm up before the gig and not switch it off till after it's finished and then I'll send it away. I don't trust my hearing to go tapping the tubes, so I'll leave it to someone else.
Clive

Ummm....sorry to break this to you, but that whole warm up/cool down thing is only to extend tube life. It won't fixed tubes that are already shot.

 

[Outlaws]

I don't trust my hearing to go tapping the tubes, so I'll leave it to someone else.
Clive

Okay, are you over 350lbs? I bet you are becuase that just reeks of pure laziness.

Go pull out the damn tubes. If you can't hear anything, ask someone else...but don't think this is a seriously indepth thing. It will be obvious to even someone that doesn't play the guitar.

 

[Farview]

Thanks guys,

I'm going to let it warm up before the gig and not switch it off till after it's finished and then I'll send it away. I don't trust my hearing to go tapping the tubes, so I'll leave it to someone else.
Clive

It will be really, really obvious to anyone. Sending your amp 1100 miles to check for a microphonic tube is like flying somone in from England to change a lightbulb in your house. There is nothing to it. Assuming you have a pencil (a pen will work) and a pair of hands, you can do it.

 

[Clive Hugh]

Okay, are you over 350lbs? I bet you are becuase that just reeks of pure laziness.

Go pull out the damn tubes. If you can't hear anything, ask someone else...but don't think this is a seriously indepth thing. It will be obvious to even someone that doesn't play the guitar.

I'll answer in two parts
1. No I'm 70 kilos or 154lbs.
2. No I'm not lazy but I am very deaf and frankly none of my associates would have the faintest idea of what I was talking about if I told them to listen to the tubes.
They might ask if I have been drinking "here, listen to these" "Oh yeah, and what do you think they might be saying?"
I do know how to remove the tubes and have done so when taking the amp between countries - New Zealand to Fiji -Fiji back to New Zealand and then New Zealand to Australia. And to lower the watts for distortion-saturated type.