• From: Florida, USA
  • Registered: 2008-06-04
  • Posts: 1,420

Topic: Marshall Amp help!?!?

Hey guys I'm in need of some assistance.  I haven't played my "big rig" in a little bit but I rearranged my pedalboard and relocated my rig into a different room.  So, when I plug everything back in I start hearing this super loud god awful hissing scream come out of my Marshall DSL.  I quickly turn the volume off and it persists.  I unplug the effects loop and the noise disappears.  The amp sounds great until you plug the effects loop in.  Anyone out there have a diagnosis for my problem?!?  I have never had this problem with any of my amps.  In particular, it's the effects return jack that when a cable is inserted the noise starts.  It sounds like the amp is about to explode when I do that. sad  Looks like it's off to the shop again...

'67 and '74 Fender Twin Reverbs, '74 Marshall 1987 lead mkII, Metro Superlead 100. Pedals from TC Electronic, Ibanez, Dunlop, BK Butler, Electro-Harmonix, Fulltone, Maestro/Gibson, Loopmaster switching, VoodooLab, Boss. Gibson and Fender guitars, Dimarzio pickups.
  • Registered: 2009-02-10
  • Posts: 470

Re: Marshall Amp help!?!?

Do you use the +db on the effects loop?
Try have the button out and see if that makes any difference.

  • Bailz
  • Bailz
  • Silver Member
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  • From: Aberdeen, Scotland
  • Registered: 2009-01-05
  • Posts: 60

Re: Marshall Amp help!?!?

Pop a cable between the send and return jacks on your effects loop. That'll tell you whether there's a problem with your loop or one of your effects.

  • gsj
  • gsj
  • BONAMETAL
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  • From: North Essex, England
  • Registered: 2006-09-21
  • Posts: 2,149

Re: Marshall Amp help!?!?

Spray some Supersivisol switch cleaner on to a 1/4" jack plug (do NOT!!!!! use WD40) and put the plug in and out of the send socket..... then do the same for the return socket. Might help.

Geoff

never give up, never slow down
never grow old, never ever die young
  • From: Florida, USA
  • Registered: 2008-06-04
  • Posts: 1,420

Re: Marshall Amp help!?!?

Thanks guys I appreciate the advice.  The FX loop is a weird thing to go haywire and has never happened to me before.  I will try this and see if it works.

'67 and '74 Fender Twin Reverbs, '74 Marshall 1987 lead mkII, Metro Superlead 100. Pedals from TC Electronic, Ibanez, Dunlop, BK Butler, Electro-Harmonix, Fulltone, Maestro/Gibson, Loopmaster switching, VoodooLab, Boss. Gibson and Fender guitars, Dimarzio pickups.
  • Registered: 2009-02-10
  • Posts: 470

Re: Marshall Amp help!?!?

The studios I go to have no JCM900s with a working effects loop. They have at least 10 900s too. Its just strange that none work. All their 2000s though have working loops.

  • gsj
  • gsj
  • BONAMETAL
  • Offline
  • From: North Essex, England
  • Registered: 2006-09-21
  • Posts: 2,149

Re: Marshall Amp help!?!?

An amp tech I know told me that on some Marshalls the loop sockets oxidise if they're not used so it's a good idea to stick a jack in there once in a while wink

Oh, and I meant Super Servisol (switch cleaner)

never give up, never slow down
never grow old, never ever die young
  • From: Detroit
  • Registered: 2006-06-02
  • Posts: 5,807

Re: Marshall Amp help!?!?

Also make sure you don't have any overdrive or distortion pedals in your effects loop.

Bailz wrote:

Pop a cable between the send and return jacks on your effects loop. That'll tell you whether there's a problem with your loop or one of your effects.

I've done this before instead of using an attenuator. I turn my Master volume to to 10 and my effects send/return down to 1 to get a different sound and have full juice going through the tubes.

There is a Marshall Forum you might be able to get help with this too:
http://www.marshallforum.com/

- Nic from Detroit... posting on JB's Forum since 6-2-2006
Ask me about my handwound Great Lakes Guitar Pickups
Since 2010, Bonamassa fans have taken advantage of my JB friend discount = my cost + shipping. cool