Marshall 1960 4x12 cabinet possible switch issue.

jcs

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8,093
I now own a Marshall 1960 slant cab with original Celestion 75's....its the stereo cabinet which is a first for me.

So, one side of the cabinet, the 2 speakers are functioning but making a slight crackling sound.

I remove the back, check all wiring, all is secure....I go ahead and replace the 2 crackling speakers with Celestion greenbacks AND I repeatedly move the stereo switch back and forth.

Now the cabinet sounds fine...both sides sound perfect.

SO, could the switch be at fault here? Could it be intermittent and me moving it repeatedly temporarily cleaned the contacts?

I tested the cracking speakers and they test fine with the multi meter....no rubbing pushing gently on the cone.

Should I replace the switch to be cautious?
 

xtian

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2,729
Sure, it could be the switch. Get rid of it. Do you ever use stereo mode?
 
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jcs

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Sure, it could be the switch. Get rid of it. Do you ever use stereo mode?
I haven't owned a stereo cab before... don't really know if I need it or not LOL!

I wouldn't mind keeping it stock and I really need the 4 and 16 ohm option.
 

gldtp99

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4,550
The switch/jacks assembly in these cabs isn't known for reliability----- I've removed many of them and wired the cabs to Series/Parallel, 16 ohms with new metal Switchcraft jacks------ this gives a rock solid 16 ohm only stage cab.
I have one of these cabs in my shop that I use to test out many makes/models of amps so the 4/16 ohm mono and 8 ohm x 2 stereo functions are very useful to me as a "bench tester cab".
I've thoroughly cleaned the switch/jacks assembly and it functions as it should---- It gave drifting, odd readings when I first got it---- I also bought another new switch/jacks assembly from CE Dist in case this one ever gets so bad that cleaning no longer puts it back into proper function mode.
I keep an eye on this cab by regularly testing DC resistance, through a speaker cable, before plugging amps into it.
IMO, if the multi-ohms function of this type of cab is important---- measure it to make sure it's working properly and keep measuring it regularly to monitor its proper function---- clean as needed.
If the multi-ohms function isn't important to the user then removing the switch/jacks assembly and wiring the cab as needed (4 ohms parallel or 16 ohms series/parallel for four 16 ohm speakers) is the safest, most reliable way to deal with these cabs.
Running a tube amp into a value drifting, flakey switch assembly on the speaker cab could cause expensive parts failures in the amp----- and most likely won't sound as good as a rock solid speaker connection.................... gldtp99
 
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jcs

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How do you clean this switch?

I have measured the impedance many times and it always measures the same in each position.

If I can get it apart and clean it I will....I see some tiny holes, is that where you squirted deoxit cleaner or can it be at least partially disassembled?

So now, I am trying to determine if the 2 speakers I pulled are still making noise.....guess I will wire 1 of the "crackly ones" with another known good one in parallel and see if the noise reappears.
 

gldtp99

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4,550
Deoxit D5---- give it a bath, don't try to take the assembly apart----- move the switch and insert plugs into the jacks several times to help clean the contacts.
If I was a betting man i'd go with the switch assembly being dirty as the source of the crackle---- but you never know: a speaker, speaker wire, or connection could have been the noisy culprit.
Sometimes just disconnecting and re-connecting those push connectors can cure a flakey connection--- I disconnected/sprayed D5/re-connected all the push connectors in my cab---- on the speakers and the switch/jacks assembly--- I'd prefer soldered wire connections but cleaned up push connectors are easier with the orig switch/jacks assembly.
If you're getting good DC resistance readings and no weird crackling noises, you're good to go !!
 

jcs

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8,093
So I pulled the switch loose and soaked it with contact wash right where the switch is and repeatedly moved the slider switch back and forth.

Then I used fader lube and did the same letting it soak in....it ran all over the place!

Everything sounds and measures fine right now....now to test the 2 speakers I pulled just to be sure....hopefully it was the switch and the 2 speakers I pulled are fine!

Thanks for the help!
 

Vanyu

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738
I see you've worked out your situation, and I'm glad it all worked out for you, but I'd like to throw in one more suggestion...

If the switch comes to be a problem again, it isn't hard to remove the switching assembly and wire the cab as either 4 or 16 ohms. If you add a 3rd hole, you can even make it 8/8 ohm stereo with a 16 ohm mono input. Or you could use a good quality DPST and wire it to have the same functionalities you have now, but with good quality parts. Google "stereo 4x12 wiring" and have a look at some of those diagrams, just about anything is possible with these cabs.
 
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jcs

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I see you've worked out your situation, and I'm glad it all worked out for you, but I'd like to throw in one more suggestion...

If the switch comes to be a problem again, it isn't hard to remove the switching assembly and wire the cab as either 4 or 16 ohms. If you add a 3rd hole, you can even make it 8/8 ohm stereo with a 16 ohm mono input. Or you could use a good quality DPST and wire it to have the same functionalities you have now, but with good quality parts. Google "stereo 4x12 wiring" and have a look at some of those diagrams, just about anything is possible with these cabs.
I think you read my mind!

I was just going to mention modding a few of my other 4x12's in the same manner.

I have this overbuilt, huge GK 4x12 straight cabinet for example that is only 4 ohm all parallel with 16 ohm speakers....pretty limited at only 4 ohms

I think a hardwired, multi impedance 4x12 with quality parts is worth the investment and time.
 




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