Whirring, ambiant noise coming from speaker cab of RM100M

[ashishk]

Hi y'all!

I recently got this amp off ebay from a dude in Brisbane for AUD$1700. It is in immaculate condition and comes loaded with Recto, 1086 and Modern modules, in that order moving from left to right across the front of the head, and 4 Ruby EL34's. It works great, and there appears to be nothing wrong with the amp; all the tubes light up, none of the LEDs at the back of the amp are on.
Bought a brand new Randall 412-XC which comes loaded with Celestion seventy80s to match with this too.

The problem is, when the amp is cranked up, and I turn down the volume knob on my guitar, e.g between songs and such, the Recto module has this wierd whirring noise, like what a fan would sound like if you put a mic in front of it. There are noticable volume drops and spikes in the level of noise. When playing normally tho, its not apparent, but it shows up when muting the strings with my palm.

The 1086 and Modern modules have their own share of background fuzz, but its more constant, leading me to believe that it may not be a problem with the input preamp tube, but most likely the tubes in the Recto module.

Any thoughts or advice on what a quick and permanent fix might be? I'm not running any effects through the series nor parallel loops. I am about to buy a few tubes off ebay in a few days, so I wanted to get a list going to save on postage costs.

Many thanks guys, and great work getting a forum like this set up!

Cheers,
Ashish K.

 

[jmgman70]

Try some new preamp tubes in the modules first.

 

[MassiveKerry]

Are you sure that it's in the cabinet?

I have noticed an exhaust fan in the RM1000M head. Which sounds like a fan. I don't love it, but when I'm playing through the amp, I don't hear it.

 

[ashishk]

Try some new preamp tubes in the modules first.

Okay. Sounds good. Now then... as this is my 1st tube amp, how do you go abouts swapping out the 12AX7s in the module? And is there anyway to test if the tube still functions before pulling it out?

Thanks jmgman70!

 

[ashishk]

Are you sure that it's in the cabinet?

I have noticed an exhaust fan in the RM1000M head. Which sounds like a fan. I don't love it, but when I'm playing through the amp, I don't hear it.

Thanks MassiveKerry.
It's definitely coming from the cabinet, cos the 1st thing I noticed was the sound of the fan whirring when I turn the amp on standby. And also, just to play safe, I moved the head away from the cab so that whatever sound I heard was definitely coming from the speakers.

But yeah, am going to try swapping out the preamp tubes after figuring out how to do it 1st.

Cheers!

 

[jmgman70]

Are you sure that it's in the cabinet?

I have noticed an exhaust fan in the RM1000M head. Which sounds like a fan. I don't love it, but when I'm playing through the amp, I don't hear it.

Thanks MassiveKerry.
It's definitely coming from the cabinet, cos the 1st thing I noticed was the sound of the fan whirring when I turn the amp on standby. And also, just to play safe, I moved the head away from the cab so that whatever sound I heard was definitely coming from the speakers.

But yeah, am going to try swapping out the preamp tubes after figuring out how to do it 1st.

Cheers!

First pull the module out.If they have the heat shield,remove the two screws on it and pull the shield off,and then replace the screws.then carefully pull the tubes out ,but they are kinda tight but wiggle alittle back and forth,then line the new tube up and push it in.

 

[ashishk]

First pull the module out.If they have the heat shield,remove the two screws on it and pull the shield off,and then replace the screws.then carefully pull the tubes out ,but they are kinda tight but wiggle alittle back and forth,then line the new tube up and push it in.

Righteous! Will get on it as soon as the new ECC83-Ss arrive. Thanks again dude!