upgrading a Marshall 1960A Slant Cab

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Groovey Records, Jan 14, 2008.


  1. Groovey Records

    Groovey Records Member

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    A friend let me have a 1960A 4x12 cab. It has Brittish Celestion T75's that I am going to swapout for Greenbacks and 12H30's.

    I was thinking while I was in there I could upgrade the wire harness to something better.

    Any suggestions on gauge and whether I should just run wire or buy a complete harness. And do you know of any sources for this kind of thing.

    I saw Mojo had an 18 gauge harness but thought I'd ask if there was somthing else more audiophile available IE Cardas or such and such?

    Thanks, I always enjoy reading the posts in this forum. This is an area where I keep my thoughts to myself and learn as much as I can.

    Regards
    Joe Tee
     
  2. rog951

    rog951 Member

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    The mojo harness is probably great, most of their stuff is. I've been using the 18awg cloth-covered wire from this place with good success: http://radiodaze.com/

    As far as audiophile-grade speaker wiring, I don't know. My feeling is that as long as the wire will carry the current, who cares? Especially for such a short run as inside the cab. There may be informed opinions to the contrary, and I'm definitely no expert, but my cabs with 18awg wire sounds great to me!

    BTW, I always had the propensity to use heavy-gauge wire for this stuff but after working a while with 12awg, I said "forget it!"
     
  3. John Phillips

    John Phillips Member

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    If it's the older JCM800-style cab with just a single jack, you really don't have to do anything other than cut off the push-connectors and solder the wires directly to the jack and speakers. The stock wire is plenty good enough - it's actually much thicker than it looks if you strip it back, it's just the covering which is very thin.

    If it's a JCM900-style cab with the switching panel, get rid of it and hardwire the cab for your preferred impedance using standard jacks (just parallel the two, it will give you a backup or a daisy-chain option). The PCB and switching junk is a cause of reliability problems as well as potential tone blockage.
     
  4. Groovey Records

    Groovey Records Member

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    Thanks folks,

    I will know more tomorrow when it arrives I am thinking mid 80's. Once belonged to Metalica and they left it behind in the studio.

    John, my family on my mothers side are Scottish, in fact I spent alot of time in Glasgow every summer growing up. I used to know the town like the back of my hand. She was born in Tollcross and her mother was in Pollock on Hardridge Road. I saw T-Rex at the Apollo!

    thanks i will check back in tommorrow

    Joe Tee
     
  5. Groovey Records

    Groovey Records Member

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    Good News

    JCM 800 looks new just some amp feet rings on top of the cab

    still
    it is a press board back and baffle with plastic handles.

    I have already swapped out the 16 Ohm T 75's

    Is there a way to tell if they truly are British made.(english) ?

    First thing I noticed was how large & fine the mesh dome over the center of the driver is.

    Large white block 1777 on the back of the cone.
    The best spyder #is G?203760 another may be CW2 03760.
    All 4 are 16 ohms.

    I put in the Greenbacks on top & the 12 H 30's on the bottom all 8 ohm.

    If I use the same wiring layout will I be ok ? If someone had a 4x12 8 ohm diagram that would be great.

    The cabinet is marked 16 ohm and it looks like it's never been opened before clean as a whistle. Top, bottom back and front inside and out.

    Can I use the serial # to date the cab?, its 33995.

    Amps on its way, will be here tommorrow night. Those nasty UPS guys have there nasty hands on it right now (shudder).

    So any help you can offer is mucho apreciado (thats french)
    I don't ask alot do I:rolleyes:

    Joe Tee
     
  6. Groovey Records

    Groovey Records Member

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    I dated the speakers as March 1988 thanks to the TGP Archives

    http://www.unclespot.com/celestion_date_codes.html

    "I have already swapped out the 16 Ohm T 75's
    Is there a way to tell if they truly are British made.(english) ?
    First thing I noticed was how large & fine the mesh dome over the center of the driver is.
    Large white block 1777 on the back of the cone.
    The best spyder #is G?203760 another may be CW2 03760.
    All 4 are 16 ohms."


    I know I have seen wiring diagrams but havn't found them yet
    I need 4x12 8 ohm from 4x12 16 ohm diagram

    Dating the cab by serial number is proving elusivive
    Amp gets here today I like to double check wiring before I plug it in

    Thanks
    Joe Tee

    "I declare that The Beatles are mutants. Prototypes of evolutionary agents sent by God, endowed with a mysterious power to create a new human species, a young race of laughing freemen."
    - Timothy Leary
     
  7. Casual Picker

    Casual Picker Member

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  8. Groovey Records

    Groovey Records Member

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    [​IMG]

    This is not the way the cab was wired

    I will try to describe-- -hope you can follow

    top left positive to H jack (red)
    top left + to bottom left + (red)
    top left - to top right + (blue)

    bottom left - to bottom right + (blue)

    top right - to jack (black)
    top right - to bottom right - (black)

    is this correct?

    A total of 6 conections
     
  9. John Phillips

    John Phillips Member

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    That's the same as the drawing but turned through a right angle (which doesn't matter electrically).

    You do want it as it is, so you have identical speakers in series (the pairs with a wire running from the + of one speaker to the - of the other).

    Turn the drawing sideways so the jack is at the bottom and that's it.
     
  10. Groovey Records

    Groovey Records Member

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    So the greenbacks on top are paired - to positive
    and the 12 h 30's on the bottom are paired - to positive ?

    if I get this right its thanks to you guys!

    This is what i have with the jack on top

    [​IMG]
     
  11. John Phillips

    John Phillips Member

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