marshall JMP Super Bass

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marshall JMP Super Bass

Postby al vintage » Sat May 02, 2009 3:31 pm

hello,
I've got a marshall jmp super bass , with plexi front and rear pannel. His serial number is SB/A 10873.
Does anyone know when he was produced.
Thank you.
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Re: marshall JMP Super Bass

Postby Brian Wallace » Sat May 02, 2009 4:26 pm

Do you have any pictures?
Remember....You can fix it with a little extra energy and a positive attitude. ;)
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Re: marshall JMP Super Bass

Postby al vintage » Sat May 02, 2009 4:57 pm

I post some pictures to front and rear of the amp in a few minutes.
Just time to recharge the accu of the camera. :lol:
I read on the web that usually there is a letter at the end of the serial no. to determinate the year of production (A for 69 and 70, B for 71 ...)But in my amp there is no letter at the end (between 67 and 69???)
Last edited by al vintage on Sat May 02, 2009 5:07 pm, edited 1 time in total.
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Re: marshall JMP Super Bass

Postby David B » Sat May 02, 2009 5:00 pm

also internal shots if ya got em :)
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Re: marshall JMP Super Bass

Postby al vintage » Sat May 02, 2009 5:08 pm

Ok no problems , bu it's actually not in use (no more pt transfo and no tubes), but i did it.
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Re: marshall JMP Super Bass

Postby al vintage » Sat May 02, 2009 5:46 pm

Front, Rear ad inside.
Image
Image
Image
Image
Image
Image
It's not in a very good condition, but it's my 15 years old birthday present from my parents (i'm 31 years old), and i want to keep it all my life , so i am going to recondition it.
Thank you for helping me, and sorry for my english, i'm french.
Last edited by al vintage on Wed Jun 10, 2009 8:16 pm, edited 2 times in total.
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Re: marshall JMP Super Bass

Postby Brian Wallace » Sat May 02, 2009 7:07 pm

First rough guess is 68. Are the pots original? If so, can you get the date codes off of them?
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Re: marshall JMP Super Bass

Postby al vintage » Sat May 02, 2009 8:00 pm

the pots are original i guess, on the presence pot it is writting AB (as a brand) then 5KΩln J8, that's all i find.
There's no date code on the rear cover of the pot.
Maybe they are not original ????
Two of the pots (volume 1 and 2) are RS brand, with plastic piece (for the knob)
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Re: marshall JMP Super Bass

Postby Brian Wallace » Sat May 02, 2009 8:45 pm

AB is Allen Bradley and J8 is 1968.

If you can get all the pots codes, this will help narrow it down as best we can for a final date.
Remember....You can fix it with a little extra energy and a positive attitude. ;)
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Re: marshall JMP Super Bass

Postby al vintage » Sun May 03, 2009 7:29 am

Volume 1: RS 1MΩLG L8
Volume 2: RS 1MΩLG K3
Treble: AB 250KΩLG J8
Middle: AB 25KΩLG H8
Bass: RS 1MΩLG H8
Thre's something strange on this amp,the top, sides and back of it are cover by a kind of carpet (i don't know if it's the right word) and not with tolex.
What's the value of this amp with non original pt and choke (maybe marstran new one)?
Thank you
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Re: marshall JMP Super Bass

Postby Smallbox » Sun May 03, 2009 10:07 am

al vintage wrote:
Thre's something strange on this amp,the top, sides and back of it are cover by a kind of carpet (i don't know if it's the right word) and not with tolex.What's the value of this amp with non original pt and choke (maybe marstran new one)?


Hi al vintage,
That covering looks like garden-variety upholstery fabric (type of vinyl) that is what we refer to in the US as "Naugahyde".
Not the first nice old amp we've seen that somebody "fixed"-up ! That logo is also too big for that era of SuperBass, as I'm certain you're probably aware...
Also, it's a little difficult to put a value on the amp with replaced parts such as a PT, choke, etc., but most guys here will vouch for the fact that you could not really go wrong by choosing one of Brian's PT's and chokes to put in there and bring that beast back to roaring life!

It's not in a very good condition, but it's my 15 years old birthday present from my parents (i'm 31 years old), and i want to keep it all my life , so i am going to recondition it.


A very wise decision! Those efforts would be a very worthwhile pursuit...
Good luck and success!

Ray
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Re: marshall JMP Super Bass

Postby neikeel » Tue May 05, 2009 2:57 pm

My guess is late 68 early 69 with the solid board and caps up top.The OT is also later set up (rotated and with clamp so more like 69

If you want a list I can let you know what would be on my shopping list :wink: but one of Brian's 1202-80 PTs would be on it with a complete set of mustard caps and some other period pieces on the board to get it back close to how it should be.

Some correct marshall tolex would be better (look for Jim's recover tutorial on Metro cabs forum).

Will never be a collectors piece but will make really nice noises if you do it right.
Neil
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Re: marshall JMP Super Bass

Postby al vintage » Wed May 06, 2009 8:27 am

Thank you to all of you.
I start to reconditionne it, and first i draw the plan of the circuit, because i think there's somme parts missing (like the two 22µf cap near the stand-by switch), and i have only 2 D10A10 diode, but not 4.
I found a layout on the cériatone site, but the ref. of composants are not exactly the same as the schématic of the 1992 i found ?
Do you think i better have to follow the schématic of the 1992 find on schématic heaven, or the layout of cériatone?
I don't find the brian's 1202-80 pt, i only find the 1204-43 and the T2562 for jmp100??
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Re: marshall JMP Super Bass

Postby Roe » Thu May 07, 2009 3:26 pm

he probably meant the 1203-80 100w power transformer
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Re: marshall JMP Super Bass

Postby neikeel » Thu May 07, 2009 6:31 pm

Roe wrote:he probably meant the 1203-80 100w power transformer


Yup, sorry slip of finger :oops:

Schematic is here on Brians website:http://marstran.com/SuperBass.gif

For the correct spec parts it is easier here:http://metroamp.com
Neil
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