Marshall JMP Bass 1986, 50W

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Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Thu Oct 09, 2008 5:36 pm

Hello,

Since few months i started to build a complete homemade plexi 50W replica, Marshall JMP Bass 1986, 50W.
I take the instructions and some of the components at metroamp, all hardware in Germany (TubeTown) and France and the transformers here, Marstran ;)

You can see (in french) all of my work step by step here: http://byennkuhl.free.fr/ee/index.php?page=tap

Schematic (12/27/2008):
Image


    Power transformer: Marstran 1202-118
    Output transformer: Marstran 784-139
    Choke: Marstran C1999

    V1, V2, V3: EHX 12AX7
    V4, V5: EHX EL34
    Filter caps: JJ
    Capacitors: SOZO
    Carbon resistors, etc...


Inside:
Image
Image
Image

Head (without tolex):
Image
Image
Image
Image



Sound/Vidéo clips: ... coming soon ...
Last edited by Ennkuhl on Sun Feb 15, 2009 10:08 am, edited 6 times in total.
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Re: Plexi Replica

Postby Ennkuhl » Sat Oct 18, 2008 2:45 pm

Fw pictures of my Marstran transformers:

Image Image

Image


Others transformers and work will be come soon, i still wait for the 784-139 ;)

---

A new step of my amp was completed, the wiring of the power transformer.

http://byennkuhl.free.fr/ee/index.php?page=tap08

Image
Image
Last edited by Ennkuhl on Sun Feb 15, 2009 10:08 am, edited 2 times in total.
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Re: Plexi Replica

Postby Brian Wallace » Sat Oct 18, 2008 7:12 pm

Very nice, keep the pictures coming. :D
Remember....You can fix it with a little extra energy and a positive attitude. ;)
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Re: Plexi Replica

Postby Ennkuhl » Sat Dec 06, 2008 10:07 pm

I have received the last transformer today :p

alltrans.jpg

http://byennkuhl.free.fr/index.php?page=tap07

More pictures when it will be finish.
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Wed Dec 17, 2008 1:37 pm

I have finished my amp a few days ago (see the fisrt post, I have edited it). I test it and it work fine except the channel 2.
Indeed the sound is very heavy and less powerful than the channel 1. Do you have an idea of my problem ?

Apart from this problem, the amp works fine, I'll post sound clips soon.
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Re: Marshall JMP Bass 1986, 50W

Postby Brian Wallace » Wed Dec 17, 2008 1:51 pm

Start by checking your input jacks. A mistake here can cause you some grief.
Remember....You can fix it with a little extra energy and a positive attitude. ;)
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Wed Dec 17, 2008 2:55 pm

Thanks.
So I will check this in the next days. I have no time for now.
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Sat Dec 27, 2008 3:07 pm

Schematic added in first post.

I'm still waiting my own cab for more checks about my problem.
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Re: Marshall JMP Bass 1986, 50W

Postby Brian Wallace » Sat Dec 27, 2008 9:09 pm

Your schematic shows a full wave bridge rectifier, are you using this or the normal full wave rectifier?
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Sat Dec 27, 2008 10:06 pm

I use the normal bridge rectifier (MP2510)
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Fri Jan 09, 2009 9:10 pm

I received my cab today.

Image
A Laney GS412I with Celestion Seventy 80 .

I will make other tests in few days.
Last edited by Ennkuhl on Sun Feb 15, 2009 10:09 am, edited 1 time in total.
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Re: Marshall JMP Bass 1986, 50W

Postby Ennkuhl » Fri Jan 16, 2009 2:34 pm

Hello everyone.

I made some measurements and they seem good. But i think i still have a problem on channel 2. Do you think there are any mistakes ?

Voltage table:
Image

I have also recorded some samples. I done this at home, so i haven't could put the volume very loud. Any samples are made with the volume between one and two. I have recorded two samples for each input.




I hope you can hear what i mean with the channel 2. I find the sound "heavy". Do you think there is a problem or no ?


I will make others samples with the volume very loud when i can.


Thanks for help.
Last edited by Ennkuhl on Sun Feb 15, 2009 10:09 am, edited 1 time in total.
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Re: Marshall JMP Bass 1986, 50W

Postby David B » Tue Jan 20, 2009 9:04 pm

Sounds like the normal #2 dull channel to me
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