marshall JMP Super Bass

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Re: marshall JMP Super Bass

Postby al vintage » Sun May 10, 2009 7:56 pm

Hello,
Do you think i can use 1N4007 diode in place of the four A10D10, or i have to use 1N5408 diode?
the two 0.22µF capacitors can be xicon 630V capacitor?
What is better? a 47K right on the nfb tap, or on the 8 ohm of the selector?
Thank you.
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Re: marshall JMP Super Bass

Postby neikeel » Mon May 11, 2009 11:02 am

al vintage wrote:Hello,
Do you think i can use 1N4007 diode in place of the four A10D10, or i have to use 1N5408 diode?
the two 0.22µF capacitors can be xicon 630V capacitor?
What is better? a 47K right on the nfb tap, or on the 8 ohm of the selector?
Thank you.


Yes you can use x4 of the 1N4007 they are 1000v and 1A rated.
Those caps are not essential. If you are set on using them I have a spare pair of the original blue/white dubiliers (1000v rated).
The NFB is a matter of taste. I like 47k on 8ohm tap but if you want it tighter (and use a 16ohm cab) then put the NFB on the speaker jack.
Neil
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Re: marshall JMP Super Bass

Postby al vintage » Mon May 11, 2009 5:59 pm

Thanks a lot,
I think i 'd try to find 0.22µf caps @1000V in france , because of the shipping cost.
For the other parts i find everything on metro amp site, include the 1203-80 ms PT. :D
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Re: marshall JMP Super Bass

Postby al vintage » Tue May 12, 2009 12:56 pm

I'm waiting for the metro amp parts in a few days. :D :D
I choose a quad of jj el 34 and 3 JJ 12ax7, is it a good choice or not?
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Re: marshall JMP Super Bass

Postby Brian Wallace » Wed May 13, 2009 8:51 pm

I have had some bad E34L JJ's lately but I don't know how their EL34 tubes are. I do like the JJ pre's though.
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 17, 2009 6:10 pm

ok, unfortunetly i bought a quad of E34L jj, i hope they'll work good on my amp. I should better ask you before for this point. :(
I recept all the parts i needed this week, so i think that for the next week-end, the amp will be finish. I tell you that and make some sample of its sound.

I have another question, i'm building a 10W amp in pure class A, i always made the power and pre-amp boards, but i'm looking for good power and output transformer. I use a single 12ax7, with one EL84.
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Re: marshall JMP Super Bass

Postby al vintage » Mon May 18, 2009 6:53 pm

Soory for my questions but there's something i don't understand:
How plug a standby switch with only two pin?
On all layouts and schematics i found , the standby switch has four pins.
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Re: marshall JMP Super Bass

Postby Brian Wallace » Mon May 18, 2009 8:55 pm

The two pin standby switch will just break the rectified DC.

The later JMP 50W and 100W amps broke the connection at the PT's secondary and would require a four pin switch.
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 » Mon May 25, 2009 1:47 pm

I have receive the new Metro amp PT (1203-80), and trying to wire it, but the colours of the wires are not the same on the diagram , so my first fuse burn for this project :(
On one side there is an orange, a red, a blue, a violet, two green and a yellow/green wires(i think for common, 120, 220, 240, heater, and heater CT)
But on the other side there is two blue, two red/blue, one yellow/red and two red , i think for HT high voltage, HT low voltage, HT CT, but i don't know which red is the bias CT and which is the 95v.
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Re: marshall JMP Super Bass

Postby al vintage » Sat May 30, 2009 7:51 am

Ok ,i found on my own how to wire the PT, and the amp is now working well.
There's a buzz on channel 2, maybe the old resistor or capacitor , i'll try to change it.
Thanks for all,i post some sample as soon as possible.
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Re: marshall JMP Super Bass

Postby Brian Wallace » Sun May 31, 2009 2:00 pm

How about some pictures of this fine build?
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 » Thu Jun 04, 2009 4:52 pm

here is some pictures of my new old amp:
Image Image Image
Image Image
Last edited by al vintage on Wed Jun 10, 2009 8:15 pm, edited 1 time in total.
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Re: marshall JMP Super Bass

Postby neikeel » Wed Jun 10, 2009 8:26 am

Are this pics before you worked on it (sorry they are a bit small to see properly)

On the pics there is a stand up transformer mounted the wrong way round.

I am sure the 1203-80 you got from Metro would be the correct laydown transformer to drop into the chassis hole and make the wiring neat and tidy :wink:
Neil
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Re: marshall JMP Super Bass

Postby al vintage » Wed Jun 10, 2009 7:43 pm

I know that is the wrong pt, i made a mistake when i order it, i took the 1203-80 ML instead of the 1203-80 Ms :oops:
You say that it is in the wrong way, i don't really know how to mount it.
The picture s are after i work on it, for the pictures before you can see them on first page.
Now i have to find a new plexi front pannel.
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Re: marshall JMP Super Bass

Postby al vintage » Wed Jun 10, 2009 8:16 pm

BEFORE:
Image
Image
Image
Image
Image
Image
NOW:
Image Image Image
Image Image

You can clik on pictures to see larger
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