Mashall JVM 215C unbearable transformer type hum, help appreciated.

[Hackingthestrings]

I just picked up a used 2017 JVM 215C off Reverb and while it sounds amazing the transformer type background hum is unbearable. It would make playing live or recording impossible, this cannot be how it came from the factory. I have all dials straight up and down, as always when I get a new amp so its not like I have the gain maxed.

I hook my DSL40H (converted CR) up to the same outlets with zero noise even with gains pinned.

Help is greatly appreciated or I am going to have to send this beast back, thanks so much.

 

[Kuga]

Maybe It has a ground cable disconnected. Take a look inside If you can see something wrong.

 

[dtier]

Is the hum coming from the speaker or the chassis? Transformer vibration would be coming from the chassis.

Edit: I'm sure you must mean low frequency hum from the speaker.

 

[Hackingthestrings]

Is the hum coming from the speaker or the chassis? Transformer vibration would be coming from the chassis.

Edit: I'm sure you must mean low frequency hum from the speaker.

And to be more accurate the sound comes through the speaker and almost sounds like FM with no station tuned, weird. It also has a power hum coming through the speaker along with the moderate static, not sure what to think.

 

[dtier]

You might want to try substituting preamp tubes.

 

[fitz]

picked up a used 2017 JVM 215C off Reverb

Seller may have filled it up with their junk glass on the way out...

 

[Resident 217]

When standby on or off or both?
Guitar plugged in?

 

[Hackingthestrings]

When standby on or off or both?
Guitar plugged in?

Standby off. Guitar in or not did not matter.

 

[dtier]

Could also be a bad power tube redplating but that would affect tone. Just in case you can look at them and notice if one is glowing the plate.

 

[Resident 217]

Maybe an easy fix like a filter cap,
For myself, if I got a really super good deal, like really good, and/plus could not get a 100% back on the return.
I would take it to a good tech.
Otherwise I would return it. It may have gotten damaged in transit.

 

[Hackingthestrings]

Thx for the input everyone. I did roll in fresh power tubes so its not that so I decided to take it to my local tech, the seller agreed to the repair. I think we have it down to either a bad socket, filter cap or maybe even a bad ground, we will know by the end of the week.

By the way I have under $1300 into this with footswitch, tax and ship, I cant complain!

 

[KraftyBob]

Check the frequency of the hum with a guitar tuner app. If it’s 100/120MHz then is pretty much a filter cap as the line frequency doubles right after the rectifier. The filter caps smooth the ripple, but if they are failing then some of the ripple gets through and that’s the hum you hear.

 

[Hackingthestrings]

A pic while we await the verdict lol

 

[Hackingthestrings]

Update. Ok after the shop tightened up the power supply on the clean channel the noise level isnt so bad but click to OD and all hell breaks loose, tons of noise, totally unusable. Thoughts? Thanks again everyone.