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FDP Forum / Amp Mods, Repairs, and Projects / Crackling noises from reverb unit

ABN

Spain

Jan 15th, 2017 05:29 AM   Edit   Profile   Print Topic   Search Topic

Dear members, have a nice 2017!

Yesterday, while rehearsing with my band, suddenly, out of the blue, my Twin Amp started making crackling noises. They were loud! I was playing with volume at 2, and the noise were equivalent in decibels to the sound of the guitar played at that time.

Soon I found out that if I turned reverb off, there were no more noise. The amp was hot, and I was in a hurry, so I couldn't wait until it cool off a bit and swap the reverb tubes. I'm planning to go today to the reharsing room to make some checks on the amp.

Have you experienced similar situation before?

pdf64

UK

Jan 15th, 2017 07:01 AM   Edit   Profile   Print Topic   Search Topic

Oh dear, how unfortunate, you are having no luck with this amp!
Certainly try a known good 12AT7 in V7 and 12AX7 in V5.
Unplug the reverb cables to the tank at either end, perhaps apply a little lubricating contact cleaner to them, and re-fit them.
Check that the outer shield contacts of the RCA plugs haven't become splayed out; they need to squeeze tightly on to the socket contact.

To stop the crackling did you turn the reverb off at the footswitch, or turn the reverb level control down to minimum?

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ABN

Spain

Jan 15th, 2017 08:14 AM   Edit   Profile   Print Topic   Search Topic

Hi Pdf64!

I'm right now at rehearsing room. The amp seems fine, now.
The tubes have couple of months...and the RCA are in good condition.

Yesterday I turned off reverb at the footswitch. I presume if I turned it off at the knob it would go away the same way.

From my experience, reverb units have lots of problems. I'm more and more leaning towards the use of reverb pedals. Unfortunately :(

Can't find out the cause of the problem :(

Why you asked if I used the footswitch or the knob?

(This message was last edited by ABN at 06:56 PM, Jan 15th, 2017)

ABN

Spain

Jan 23rd, 2017 03:13 PM   Edit   Profile   Print Topic   Search Topic

Hi!

Check this out: https://youtu.be/uwI5NvADJoQ
In fact, noise occurs even with reverb off. The reverb amplifies it!



pdf64

UK

Jan 24th, 2017 11:18 AM   Edit   Profile   Print Topic   Search Topic

"Why you asked if I used the footswitch or the knob?"

There's a gain stage V5a between the reverb mute circuit (actuated by the footswitch) and the reverb control.

Coral Head

Sunshine State

Groupies needed
Feb 11th, 2017 04:36 AM   Edit   Profile   Print Topic   Search Topic

I have never heard that the Twin Reverb has reverb problems. Mine is from 1969 and the reverb always works perfectly. I think you have a small problem that can be easily fixed.

FDP Forum / Amp Mods, Repairs, and Projects / Crackling noises from reverb unit




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