Problems with jack plate on 1960 lead cab

Discussion in 'Marshall Amps' started by ampbassist, Nov 8, 2009.

  1. ampbassist

    ampbassist New Member

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    i have a marshall 1960 lead cab and the imput jack is crapping out on me.

    i have to bend and apply pressure on the cable for it even produce a sound. its not the cable because ive tryed 3 different ones.

    is this a fixable problem or do i have to replace the entire jack plate its self
     
  2. thrawn86

    thrawn86 Well-Known Member

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    You can take the back off of the cabinet, but don't pull it away too quickly, because you'll have to unscrew the jack plate and feed it through the hole on the rear panel. After you do that, look for bent pins and solder that's cracked/missing. You should also check all the speaker connections while you're in there. If it needs some solder, you might be able to do that yourself, but if the jack is shot, they aren't too pricey to replace either.

    Hope this helps.....:band:
     
  3. American Viking

    American Viking Well-Known Member

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    It sounds like the life scorpion is about to sting the hell out of you...

    I gotta fill you in on a couple things, first off...

    Running an amplifier with no load connected is severely damaging to the output transformer. If you are not getting sound out of the cabinet and the input is bad, then you can't just jiggle it to get it to work, every second that the signal is not under a complete path your output transformer is shorting and frying.

    Second, I hope when you swapped cables you are only using speaker cables and not instrument cables. Speaker cables are a thicker gauge that is meant for transferring current as instrument cables are thinner and cannot handle it. This again, severely damages the amplifier

    Third, we need to know if you have a single input or if you have the MONO/STEREO input jack.

    Either way, your solution is simple...
    If it is the single input jack, just replace it. If it is the MONO/STEREO jack, then I would recommend taking the PCB out and hard wiring it for 16ohms and only use a single input. If it is the MONO/STEREO jack you will have to rewire all the speakers too, but this is really simple and you can do it without any tools. You will need a soldering iron to at least make the final connection to your input.

    Wiring a 4 X 12 Speaker cabinet
    Here's all the wiring diagrams you should need.

    I highly recommend you do some research on matching impedance because this is also vital to the life of your amp. Based on what you said earlier I'm thinking you may not know the importance of this.

    Let us know how it goes and I'll try to take care of any more questions you might have. Hope you don't think I sound rude because I'm not trying to be, these amplifiers aren't toys and unfortunately no one tells us everything we need to know when we purchase them.
     
  4. ampbassist

    ampbassist New Member

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    American viking -

    hey thanks for your reply

    its a mono/stereo jack.

    i took it apart to check for solder cracks like thrawn suggested and it was wierd, when i took the cab apart and tryed getting sound of the speakers, it worked fine on stero on 16ohms but nothing from the 8ohms imput, either on mono or stereo.

    but when i put the cab back together then it stopped working. it was wierd, like the jack itself was not reaching the imput all the way, i check to make sure everything was tight as far as screws holding the jack plate in place and the wires were assembled correctly by useing the wiring digram you sent and it was correct.

    so once again im unsure

    if you have any other ideas of if you think i should just go ahead and rewire the cab to a single imput at 16ohm please let me know, i would hate to have to buy another cab.:Ohno:
     
  5. Adrian R

    Adrian R Well-Known Member

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    **I just experienced a similar situation with my 1960 cab. The solder joints that connected the receptacle pins for the jack wires had broke, and if pushed upon came free from the jack/plate pcb board. Although it was not creating an issue at that moment I could see that it would in the future. For me it was an easy fix as I just reiforced those solder joints with fresh solder.

    It sounds as if the actual switching mechanisim on that plate has failed, and even you can do what AV suggests, the easiest thing to do probably is just replace that entire jack/plate assembly. They cost about $50.00.

    In the meantime I certainly would not attempt to use that cabinet untill its fixed! AV is absolutely right about the abuse a zero load is on any tube amplifier...
     
  6. American Viking

    American Viking Well-Known Member

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    If it is a 1960 cab there is no 16ohm Stereo input. It is 4ohms Mono on the left, 16ohms mono on the right and when switched to stereo both sides are 8ohms and each jack only controls two speakers. Mono uses all four. You never need to use stereo unless you are hooking two amplifiers to the same cabinet.

    Your head must be matched to your cabinet. If the cabinet is set to 16ohms, the head must be at 16ohms, and so on and so on. This only changes if you add more cabinets. You must match the impedance.

    This leads me to believe if you have a DSL100 or newer Marshall head, some will shut down and not send signal or current when the impedance is mismatched.

    Do you own a multimeter? You can verify the jacks on the cabinet and see exactly what is wrong with it.

    The Cliff jacks in the cabinet do no usually go bad, there is usually a problem with the switch failing or cracks in the PCB.

    I would recommend just hardwiring it for one 16ohm input. Even for this, I also recommend having and being able to use a multimeter to check behind yourself. You can verify the impedance after you are finished the wiring to make sure you didn't miss something like accidentally crossing a + or - wire or something. Wiring a cabinet and using a multimeter are super easy and the tools you need are cheap.
     
  7. thrawn86

    thrawn86 Well-Known Member

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    Almost sounds like something's up with your wiring. If you pull the back off, plug in, and everything works right, and then it won't when you put it back together, it sounds like a wire is broken or shorted. Definately DON'T use it until you find the culprit, or buh-bye amplifier.
     
    MonstersOfTheMidway likes this.
  8. ampbassist

    ampbassist New Member

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    thanks for your reply guys, i think i may just replace the entire jack plate, sounds like one the easier ways to handle this.

    i dont know if it makes a difference but im actually useing a valvestate vs-100 head
     
  9. JONdoTCON

    JONdoTCON New Member

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    I have a 1960A cab that is having problems. When i plug my JCM900 head in, it only works if i set the plate switch to stereo and plug into the right jack. Even then, only the right side of the cabinet produces sound. When set to mono, i get no sound and when set to stereo and plugged into the left jack, i get no sound. I'm guessing i need to replace the jack plate, but if anyone can think of another solution, it would be apprecaited.
     
  10. Makerock

    Makerock New Member

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    Just bend socket plates strips, so you get 8 and 16 ohms in mono setting.
     

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  11. American Viking

    American Viking Well-Known Member

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    Resurrecting an old thread...

    Chances are nobody is using anything but one setting on the jack. Best solution is to remove the PCB and hard wire the cabinet to 16ohms. As long as you know how to make a strong solder joint there will be no more problems.
     
    Ken likes this.
  12. Ken

    Ken Well-Known Member

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    That means an open load is okay; at least you weren't damaging the amp while it was in failure mode.

    Ken
     
  13. FFXIhealer

    FFXIhealer Well-Known Member

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  14. SmokinDaveWolfe

    SmokinDaveWolfe New Member

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    I had the exact same problem with a 1960 Lead cab... (like yours) mine also has the stereo/8/16 ohm jack plate... It was cutting out at gigs and I noticed that if I wiggled the cord where it plugs into the jack it would cut in/out... I taped it over to one side to finish the show. the following week, when I had time to remove and inspect the jack this is what I found... the traces on the circut board had hairline cracks where the edge of the input jack solder joint thins out into the foil trace... one fix could be to solder back over it, but this is not good enough for me. (like your other reader suggested) i hard wired my cab to 16 ohm mono, and that's the cheapest and most reliable fix.. (getting off topic) we thought we liked having a stereo cabinet around because somewhere around here there is a rack mounted JMP tube pre and 9200 el34 dual monoblock power amp, and I thought someday we may want to use it with a single stereo 4x12 cab, but it never happens, rack mounted rigs are kinda like trying to re-invent something for no practical reason.
     

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  15. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I use mine in stereo w/ my EL34 50/50 & it works flawlessly. The guy that had it before me, toured hard w/ it. He switched the plastic nut on the 16ohm input to a beefy metal one & hadn't had any problems w/ it. He used it w/ a 900 @ 16ohm.

    I use the 16ohm in when I'm not using the stereo setup.
     

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