Jvm Clean Channel Orange Only?

[BigFeet25]

Hi
I have had a JVM410H for 3 years from new without any issues and am loving it.
However without any warning (pops bangs or other signs) the clean channel now makes a loud mains-frequency buzz. This is true whether guitar is plugged in or not, also whether effects loop leads are in or not. Green is still very clean and red noisier but no different from when new.
I admit that the valves are all original but suspect that as all other channels and modes appear 100% this may not be needed?
Also as a self confessed tight git I don't want to change them unnecessarily.
Any ideas gratefully received!

Thanks
BigFeet25

 

[ampmadscientist]

Hi
I have had a JVM410H for 3 years from new without any issues and am loving it.
However without any warning (pops bangs or other signs) the clean channel now makes a loud mains-frequency buzz. This is true whether guitar is plugged in or not, also whether effects loop leads are in or not. Green is still very clean and red noisier but no different from when new.
I admit that the valves are all original but suspect that as all other channels and modes appear 100% this may not be needed?
Also as a self confessed tight git I don't want to change them unnecessarily.
Any ideas gratefully received!

Thanks
BigFeet25

It could be a bad preamp tube.
No you do not need a whole set of tubes...
It may be a switching circuitry failure, such as a worn out relay.

But buy 1 new 12AX7 preamp tube, and swap the preamp tubes out with the new one, one at a time.
Retest each time you swap one out.
If it is a tube you will find which one.
Otherwise (if it's not a tube), take it to the service center where there are experienced techs and test equipment.

 

[BigFeet25]

Hi Ampmadscientist!
Thanks for coming back to me. This sounds like something I can check for a good start.
I'll post back once I get to the bottom of this.
Thanks again.

 

[BigFeet25]

Hi Ampmadscientist,
I got a new ECC83 from Hotrox here in the UK - a JJ - which was tested by them prior to shipping for suitability for use in V1 or phase splitting position V5. I swapped them one by one and got an immediate improvement when swapping it with the original in V1.
I'm sure it is just my (now) over-sensitive ear but OD1 and OD2 on orange with gain around 12 o'clock seems noisy. However, this was the same before I swapped the V1 so I'll ignore this for now!
Thanks for your steer.

 

[ampmadscientist]

Hi Ampmadscientist,
I got a new ECC83 from Hotrox here in the UK - a JJ - which was tested by them prior to shipping for suitability for use in V1 or phase splitting position V5. I swapped them one by one and got an immediate improvement when swapping it with the original in V1.
I'm sure it is just my (now) over-sensitive ear but OD1 and OD2 on orange with gain around 12 o'clock seems noisy. However, this was the same before I swapped the V1 so I'll ignore this for now!
Thanks for your steer.

I'm happy you got it to work. It is normal to get some hiss / hum in a high gain amp when it's cranked up.