Need help MKIV Big volume drop while playing

[Lights Out]

Hi
Every now & then my MKIV dramatically drops in Volume. it used to happen now & then but last night it kept doing it !

I would turn it off , start up again & It would be all right for about 30 seconds & then drop in volume again .

I thought it might be the tweed or Class A switch acting up & droping the volume but it happends while there in action too.

Im also getting a strange sound coming out of the speaker like russeling paper.

Does anyone know what could be causing this ?

Thanks

 

[zeppman]

If it happens on all channels, its the power tubes. If it happens on only one channel, its probably that pre-amp tube.

 

[Monsta-Tone]

Take a small, known to be good, patchcord and insert it into your Loop's Send & Return. Sometimes the Return Jack wears out and will cause this type of problem. Especially in a Combo since it gets much more vibration.




As far as Tubes go: I would start with Preamp Tubes since they are cheaper.

Look at your manual.

If it happens on all Channels: There are at least 3 tubes that affect both channels. Swap these out 1 at a time (placing the amp on Standby, or even better, turning it OFF), and allow the new tube to warm up properly before taking the amp off of Standby.

You can follow this same procedure if the problem is isolated to a certain Channel.

Hope this helps.





If none of these work

 

[Lights Out]

Thanks for the info guys . I'll look into those suggestions
I hope its something minor
I was thinking the Transformer was dying on me !