MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

[BUILD] SEM VCF
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3 ... 18, 19, 20  Next [all]
Author [BUILD] SEM VCF
moogah
For the moment I'm just getting this thread together as a placeholder, look for more detailed info soon!

Link to BOM:
https://docs.google.com/file/d/0Byb1hJRK5lw6OU9ZRmpGVy1yM1U/edit?pli=1

Link to Synthcube site for ordering:
http://synthcube.com/cart/index.php?route=product/product&product_id=1 77

Link to original thread:
https://www.muffwiggler.com/forum/viewtopic.php?t=69431

The PCB with component values:


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

My schematics:



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.

If you're building to use a Clarke68 Panel, the Frequency pot will be off board!
moogah
Stuff to take note of:

The pots mounted on the board are:
Frequency
Resonance (with the *)
Variable response

If you're building this for the clarke68 panel the frequency pot is mounted off board!

The 100n SMT caps can be left off if you really just don't want to deal with it.

The .150nF caps listed on some of the BOMs are actually .150uF! These values were correct on the last one of synthcube's Mouser orders that I saw.

The TL074 is marked with a '$' BUT it needs to be installed for all versions of the build!


Some info on wiring, for those who can't wait for a nice diagram smile

OK, using this image as a reference: http://www.baud-rate.com/sem_vcf.jpg

The pins on the inputs are (left to right) signal, gnd

The pins on the outputs are as labeled

The topmost 3 pin header on the right side is for the attenuverted frequency cv. The middle pin connects to the wiper, the topmost pin connects to the full ccw side of the pot and the cw side of the pot is where the signal coming in from the jack also connects, so that lug of the pot will have one wire coming from the jack and another wire going to the bottom pin of the header.

The next one down is a 2 pin header for 1v/oct resonance tracking. We're not using that one.

And nestled in between the two resonance cv pots is the un attenuated CV input. If you first wire the cv input jack so that the ground wire connects to the ccw side of the pot and the signal wire connects to the wiper, the connect the ground wire to the top pin of the header and the wiper to the bottom pin
qfactor
Awaitin' applause
moogah
DERP. Bump for updating the first post (last night).

More/better docs to come.
raisinbag
Hey, so do pots mount on component side? It looks like it from diagram, just double checking.
moogah
Good question! The pots are mounted to the component side of the board.

HOWEVER, if you're building for a Clarke68 panel the Frequency pot (on the top) is left off.
raisinbag
Ok one more question, Well two more. 1- How important are the IC suffixes? (ie can we use subs (or should avoid certain suffixes or should we stick to the BOM like gospel) and 2- are there component options for 12v vs 15v? gota watch dem SemSqanches in this neck of the woods!!!!!! Rasta-nana
Dego
Suffix not important
moogah
Ah, I am forgetful!

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.
raisinbag
Great, that's all good news. Looks like I have all parts EXCEPT 4302. I know SB has a workaround for it, anyone know what that part number is actually called? They may have one at my favorite store full of crazy old stuff.
LED-man
raisinbag wrote:
Great, that's all good news. Looks like I have all parts EXCEPT 4302. I know SB has a workaround for it, anyone know what that part number is actually called? They may have one at my favorite store full of crazy old stuff.

On ebay uk you can order J202 - look in the other orderl thread at beginning for equal parts.
raisinbag
Right on! I have some 202s in bin, woo hoo. Thanks missed that paragraph.
logicgate
LM3080 is CA3080???


EDIT:

yes it is... lol
raisinbag
I use them interchangeably often. I'm sure it will work to use ca.
logicgate
raisinbag wrote:
I use them interchangeably often. I'm sure it will work to use ca.



Hummmm I got a bunch of CA3080 that I got exclusively for this project! eek!


EDIT:

Ah you said "it will work", I thought you said it wouldn't... lol This is fun!
logicgate
Are the pots 50K linear? It doesn't say on the BOM.

And I never seen pots with 5 lugs!
raisinbag
Pretty sure they are Lin. And I'm also pretty sure the five holes are so that you can use 9mm or 16mm pots.
moogah
All of the pots are 50K linear.

The 5 pin footprint is so that you can use pots with either a .100" or .200" spacing (typical for 9mm and 16mm pots).
Barcode
Couple questions. I built the original version of the VCF.... Is it correct to leave off the $ stuff?

Does this look correct? (I know that the top pot is Freq but what are the others.) I built mine this exact way (excluding the 2 bottom trannies from the $ build) and I get no sound...

raisinbag
I'm still a bit in the dark as well, but only thing I noticed (which made me MY ASS IS BLEEDING For a second) was you have a 4305 in place of 4302. No biggy but I just thought I finally had all I need and d'oh! Some other rare tranny.
Barcode
Oops. I meant 2n4302.
moogah
Sorry guys, work has gone into overtime these last few days and I've not had enough time to finish these docs right!

what you posted looks right barcode (minus the 4305 part:)), but there is one important thing I forgot to include! The three pin header on the top right of the board is the attenuverter pot for frequency CV. The filter will behave rather poorly if this isn't connected! It's a 50K pot like all the rest and it's connections are a 'straight-through' ccw, wiper, cw (or vice-versa)


I've got a panel image from clarke68 that I need to do a wiring diagram for and I also need to post schems! This is all on my agenda and a high priority, but it's tough when I'm working 12-14 hrs a day confused
raisinbag
It's all good no stress. I was just having fun with barcode because of the mislabeled tranny. Spring brings lots of overtime for me as well.
synthcube
Moogah, please check your BOM... You list C2/C10 as .150nF , are they instead .15uF?

Raisinbag, are you/did you install the smt caps C1, C11-C17?
Barcode
I've double check every solder joint, swapped out the 3080's for known good ones, and yes I've installed the smt caps, but I still have no sound. FYI I'm building the original version, so I left off all of the $ parts. My next step would be to swap out the NOS 2n4302's I picked up (the seller had sold 40 of them with + feedback on every one) with a couple J202's. Before I start desoldering does anyone have any other suggestions?
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3 ... 18, 19, 20  Next [all]
Page 1 of 20
Powered by phpBB © phpBB Group