Swelling volume and marshall "refresh" questions

[BloodRose]

Was playing my JCM800 at low volume (trying) and the volume was slowly swelling upward. Didnt keep going and going, but didnt stay at the level I started on. what could cause? Fix? I know they are loud amps, but seems this goes from subtle to unruly with just a hair turn on the volume knob.

Also, some of the ports where you plug in cables (speaker jacks etc) are chipping and looking worn. Those hard to change?

 

[Edgecrusher]

Re: Swelling volume and marshall "refresh" questions

Let me make sure we are clear are you saying when you play without touching any knobs that the volume gets louder and louder? Or just that when you turn the knob it gets louder quickly? If the 2nd it coudl jsut be the taper on the knob. I have a 72 small box Marshall 50 watt that goes from broken AM radio loud to peel the paint off your house between 2.5 and 3

If its the first a few things can cause this. It could even be that one of your speaker jacks that is chipping and worn isnt connecting so good. Beyond that clean the pots and all the jacks, make sure they are tight. Also clean and check the tube sockets. Most guys will rush to tell you its the tubes going bad but I find more often then not that isnt it. Sure tubes go bad but not nearly as much as people around here would like you to think. If the amp has been sitting awhile its probably dusty and corroded the cleaning will do it some good.

 

[koshikas]

Re: Swelling volume and marshall "refresh" questions

Was playing my JCM800 at low volume (trying) and the volume was slowly swelling upward. Didnt keep going and going, but didnt stay at the level I started on. what could cause? Fix? I know they are loud amps, but seems this goes from subtle to unruly with just a hair turn on the volume knob.

are u complaining? :wrf:

 

[Lake Placid Blues]

Re: Swelling volume and marshall "refresh" questions

This could be the filter caps draining down and then slowly building back up if your not changing any settings.

 

[BloodRose]

Re: Swelling volume and marshall "refresh" questions

Let me make sure we are clear are you saying when you play without touching any knobs that the volume gets louder and louder? Or just that when you turn the knob it gets louder quickly? If the 2nd it coudl jsut be the taper on the knob. I have a 72 small box Marshall 50 watt that goes from broken AM radio loud to peel the paint off your house between 2.5 and 3

If its the first a few things can cause this. It could even be that one of your speaker jacks that is chipping and worn isnt connecting so good. Beyond that clean the pots and all the jacks, make sure they are tight. Also clean and check the tube sockets. Most guys will rush to tell you its the tubes going bad but I find more often then not that isnt it. Sure tubes go bad but not nearly as much as people around here would like you to think. If the amp has been sitting awhile its probably dusty and corroded the cleaning will do it some good.

Im saying I dont touch the knob and it gets louder. But yes, it also goes to deafening with VERY little volume dialed up. My concern is the initial swell without touching the knob.

are u complaining? :wrf:

I love it loud, so wouldnt be complaining if I wouldnt get evicted for the volume..

 

[Gearjoneser]

Re: Swelling volume and marshall "refresh" questions

Are the pots worn? Otherwise, I'd recap it with a bunch of JJ filter caps of the same value, and make sure the power tubes are good. Filter caps aren't much different than soldering a pickup into a guitar, other than the fact you've got to drain their stored current to ground before putting your soldering iron to them.

 

[zzmoore]

Re: Swelling volume and marshall "refresh" questions

It COULD be so many things.
As always, replace tubes, and check all the cables and connections that you can.
Remove and reinstall tubes a few times...cables as well.
Clean all pots and jacks.

You always need to be specific as possible. Does it JUST do this at at some certain time...always...start up...after 30 minutes.?
Can you pull a chassis and work on a live amp.?
best

 

[BloodRose]

Re: Swelling volume and marshall "refresh" questions

Are the pots worn? Otherwise, I'd recap it with a bunch of JJ filter caps of the same value, and make sure the power tubes are good. Filter caps aren't much different than soldering a pickup into a guitar, other than the fact you've got to drain their stored current to ground before putting your soldering iron to them.

Alil back story. I bought this amp off of Jmoose a few years ago. IIRC he listed it as having recently had new filter caps in it and I havent played it a whole lot. Not saying it isnt this, but I wanted to throw this out there.

ZZmoore, I think(if this makes sense) that I may be trying to play it lower than it will go. (although I think it should stay where you set it) I try to set the volume to where its barely on, but I dont think the amp can really function at that low level so it fills in. But yeah, Im gonna have it gone thru soon as I get some $$. It sounds amazing once its roaring

 

[Edgecrusher]

Re: Swelling volume and marshall "refresh" questions

If its been sitting its more than likely just dirty and needs cleaned out... Dust is a big cause of this sort of weirdness

 

[zzmoore]

Re: Swelling volume and marshall "refresh" questions

Alil back story. I bought this amp off of Jmoose a few years ago. IIRC he listed it as having recently had new filter caps in it and I havent played it a whole lot. Not saying it isnt this, but I wanted to throw this out there.

ZZmoore, I think(if this makes sense) that I may be trying to play it lower than it will go. (although I think it should stay where you set it) I try to set the volume to where its barely on, but I dont think the amp can really function at that low level so it fills in. But yeah, Im gonna have it gone thru soon as I get some $$. It sounds amazing once its roaring

What if you don't have the amp "set to where it is barely on"...?
Do you still get the same volume swells.?
As has been mentioned, you may have a bad or dirty pot.

 

[BloodRose]

Re: Swelling volume and marshall "refresh" questions

If its been sitting its more than likely just dirty and needs cleaned out... Dust is a big cause of this sort of weirdness

I keep it covered, and have blasted it out with canned air, but could be

What if you don't have the amp "set to where it is barely on"...?
Do you still get the same volume swells.?
As has been mentioned, you may have a bad or dirty pot.

No, screams like a banshee at any other volume level. so, could be as above. Im thinking maybe it just cant find it in its heart to play that soft. Its like, I MUST scream!!! Ill clean out the sockets and all and see what happens

 

[Edgecrusher]

Re: Swelling volume and marshall "refresh" questions

I can see it sounding weak and tinny when its low... but the variation points that maybe the pot wipers are only dirty in that area