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Projecttitel: Oberheim SEM VCF in MOTMStatus: one finished in 2013, one in shedule 2015Startdate: 2013Duedate: 2013/2015updated : 02/2017Manufacture link: http://www.muffwiggler.com/forum/viewtopic.php?t=69431 |
INFO: due to some major/minor issues with the pcb layout, i canceled the second building.
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update 02/2017: i repaneled the Filter to a MU Format Panel from synthcube.com
Here the latest Builders Guide from 2014 (with all known bugfixes)
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change the 300pF kerko to silver mica 300pf (Silver Mica/Glimmer Kondensator)
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General
Link to original thread:
http://www.muffwiggler.com/forum/viewtopic.php?t=69431
The original schematics (page 6), all components not marked with a '$' are the exactly the same as the original with this layout.
http://www.synthfool.com/docs/Oberheim/Oberheim_SEM1A/Oberheim_SEM_1A_ Schematics.pdf
If you orient the board so power is lower right- the order for the transistors from top to bottom is as follows:
2n3904
2n3906
2n3906
2n3904
The 2n4302's go into is located in the two unlabled unlabeled spots in the middle of the board, using only 3 of the five holes the 3pins (middle position)
from muffs:
There are 3 100n SMT caps mounted on the bottom of the board. If you really don't want to deal with SMT, the filter will still work without them.
The components marked with a $ are for the version with VC Resonance.
The components marked with a * are for the original version, but they are left off on the vc res build.
the FET buffer transistors (2N4302 on the original) are the two in the middle of the board in this picture. The silkscreen shows the correct orientation for the 4302, but there are two additional pins which make it easier to use a substitute without having to bed pins.
The 2n3904 and 2n3906 pair are poorly labeled (not labeled...). They are the two without any markings and the 2n3906 is the one with a trace connected to its middle pin.
you will probably need to stretch the pins of the 5pF capacitor above the LM301. To be sure, just don't let it's leads touch the board directly.
There are 3 150K resistors on the board, all three will be 120K instead for a 12V version. However, one of the 150K is only needed for vc-res, so you can ignore that one.
The inputs are on the bottom left and the pins are: Input, Ground.
The outputs are on the bottom right and the pins are: Ground, LP, HP, BP, Variable.
The pots mount on the component side of the board.
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