Fender supersonic 60 head.....Crackling in clean channel help please!

Fortheloveofguitar

HI Guys

I bought a used supersonic 60 head off ebay and it arrived to day. Overall the amp is fantastic sounding and perfect for what i need, only there is a slight problem with it on the clean channel.

Every now and again i can hear a little crackle in the background when im playing. Its very quick and sounds like the crackle you would get from the scratchy pot but only lasts for a second or less.

Could it be a valve problem? If so what to look at first?

I will be honest in that it looks to me that the valves could be the ones it shipped with from the factory still as i can see that the power valves have' fender' groove tubes stamped on them which would make them quite old as this is a Mk1 model amp.

Hoping you can shed some light on it or if ive been sold a lemon and need to send it back.

Thanks

crunchman

Dodgy valves can make weird noises - I had frying pan type sputtering a few times.  Sometimes they go dull sounding and lose volume.  I would imagine that crackling is possible.

You can swap pre-amp valves yourself no problem.  According to the Fender website it has 6 12AX7 and 2 12AT7 preamp valves.  It's unlikely that they are all bad.  You could probably buy a 12AX7 and a 12AT7 and swap out preamp valves one at a time.  If you find the crackling goes away then you have found the dodgy valve.

If you already have another valve amp then it will almost certainly have at least one 12AX7 pre-amp valve so you could borrow one from it for testing with if you don't want to spend any money. 

The other thing to be aware of is that 12AX7 is an American designation.  ECC83 is the European equivalent and can be used in its place.  An ECC81 is the European equivalent of the 12AT7.

Power valves will need biasing.  You need to know what you are doing with that!  Most amps you need to open the amp up, and take measurements with it on.  There is likely to be 450V plus (DC) on the plates of the power valves of this one so unless you are absolutely sure what you are doing you should take it to a tech.

57Deluxe

swap your guitar leads over... so often noise is not the amp at all!

ICBM

It can also be other noise that's being picked up - some amps and even some channels on the same amp are much more prone to it than others. One of my amps makes a little crackle like that every time the fridge turns itself on, and it's at the other end of the house. Took me ages to work out what it was - I finally realised when I had left the amp on and turned up a fair way, went through to the kitchen to get something, and heard the fridge come on and the amp crackle from the other room at the same time.