[build] dual 281 boards

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lessavyfav
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[build] dual 281 boards

Post by lessavyfav » Fri Oct 19, 2012 6:14 pm

:nana: :bacon: :banana: :bacon:

Tobbobrillo said it was ok for me to open this thread!

First thing is... Thanks Rowman for your BOM. Sorry if it is lame to quote you here aesthetically but it is a great kickoff...
rowman wrote:Ok take 2:

Revised 281 BOM

Now the only things not on the BOM are the L7810, MPF-102, pots and switches.

Edit: I put in polypropylene caps for .1uF, would c0g mlcc be better? The ones consumed listed are double the price of the polyprops though.

Also updated BOM, polypropylene caps had too large lead spacing.
I am hoping to build the quad euro version and plan to stuff the boards in advance! (Famous last words)


:->: EDIT: 11/12/12-
Cribbing shamelessly off Rowman, I went with these high voltage super caps mentioned here:
rowman wrote: Also in my personal spreadsheet I've changed my 47nF film caps to these polypropylene ones instead of polyester
They have a bigger footprint then the board want's to accomodate. I just kinda left mine sitting over the neighboring resistors, hopefully that isn't a problem.

The .1uf caps in the BOM had the same chubby case size. I checked some other caps I had and 2.5mm wide x 7.2 long x 6.5 high seem like the expected case size. FWIW, Mouser part: 80-R82EC3100DQ70J look like the right size for the .1uF and, for the .047uF, Mouser part:
80-R82EC2470DQ60J looks like the right size. You need 2 of each per board.

alternately, for the .1uF caps Consumed suggested the following:
consumed wrote: here's another "high quality" .1uF cap. this is not polypropylene or polystyrene, but c0g mlcc
double check the lead spacing on the board if this is a concern (i dont have mine in front of me)

Mouser part: 810-FK26C0G1H104J
Last edited by lessavyfav on Tue Nov 13, 2012 10:50 am, edited 4 times in total.

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rowman
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Post by rowman » Sat Oct 20, 2012 12:11 am

No problem, I'll quote emmaker here too for the regulator:
emmaker wrote: Probably a LM7810 since it's in a TO220 package. Check the pinout and pick your poison.

http://www.mouser.com/Semiconductors/Po ... 10&FS=True
Also in my personal spreadsheet I've changed my 47nF film caps to these polypropylene ones instead of polyester, and my electros to these and these. It only costs a couple dollars more per build to get better quality caps so I figure why not. I know the electros are for power filtering but I'm thinking the ones with a higher voltage rating and temperature range will last longer before the module has to get recapped.

But I'm learning all this stuff as I go so take it all with a grain of salt.

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bsmith
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Post by bsmith » Tue Oct 23, 2012 9:11 pm

The 1k* resistors that say in the bom "r7,r8 for 12v operation use 1.2/1.5 here'.... Is this just 'choose one value for both' or is it 1.2 for r7 1.5 for r8...or.....?

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consumed
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Post by consumed » Tue Oct 23, 2012 9:32 pm

dual 281 pdf says 1.2k for those two resistors.

edit
ive built five of the single v3 boards, and i may have used 1.2k on one and 1.5k on the other. ill have to go look now
:doh:

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Post by bsmith » Tue Oct 23, 2012 10:57 pm

Thanks for response, sorry for question that was answered right there on the wiring PDF. Took the box of components, my boards, and the bom sheet from the single boards with me to stuff and tick parts off the list while watching a movie with the family - had that bit about the 1.2k/1.5k on there and it gave me pause....
So, stuffed and ready to go, will take a crack at wiring in the next day or so, at least try slapping some temporary panel together to have something to play with while the panel and daughter cards get finished. Gonna take it slow on the wiring, a bit more going on with this one than on previous projects, wiring-wise (and I'm doing the twf as well, which wow, a lot going on with it doing the pots and jacks as well).

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Post by bsmith » Tue Oct 30, 2012 10:01 am

allright - so have one board half up on my euro 12v supply - the A side is working like i want to see - the b side however is no diggity - i'm measuring a little over 11v coming from the B out at all times on it - but i can't for the life of me see where i've gone wrong, probably something with the wiring on that B+, but i'm not spotting it. replaced all ic's, double checked electro cap polaritys, regulator is outputting 10v from that pad, diodes facing the correct direction. transistors are in the right place (however what does the 's' part of 3906s silkscreen mean? Using 2n3906 there).... gone over all the connections on the wiring diagrams and it all seems correct.. Puzzled. Obviously can't tell if the quadrature is working correctly, but I can tell that 'peak' out is working just because as I pull the pot up that 11v from the B overtakes the A side cycling or whatever.
It's fun playing with the A side though!
Any ideas?

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Post by bsmith » Sat Nov 03, 2012 8:37 pm

so after ripping that first board completely apart like three times and always getting the constant voltage deal on the b side i built up my second board and hooray right out the gate both sides are working, quadrature is happening, this thing is badass! really this is super fun. Hooray!
Did have one question about cycle mode - I understand after browsing through the build thread at e-m that the cycle mode needs a kick in the but from a trigger to get going - is there some method anyone experienced with building these is aware of where 'flip the switch, it starts cycling' is possible?
Unrelated, with the trims cranked all the way over I'm getting around 450hz in cycle mode with no cv applied and a/d all the way down - have been reading that these are typically trimmed to 1khz. Not a big deal - fast enough for me, but would be cool to be able to get higher into audio range. I'm running this on 12v btw...

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Post by toppobrillo » Sat Nov 03, 2012 10:37 pm

hey great you got it workin. there is a mod, a sort of 'start capacitor' that Roman noticed on the Easel pulser circuit that can be added here to initiate cycling when the switch is closed. ill put it up on my site. I still don't know for sure for sure but I've always assumed the 'standard' operation of the old 281 was as-is. the 281e may self-start not sure.

the range is pretty close, 1mS rise and fall times [as indicated on the panel as min time] would give u 500Hz when self-cycling. what value resistors did you use for R7 and 8? on 12V they should both be 1.5K.

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Post by bsmith » Sat Nov 03, 2012 10:49 pm

Thanks Josh.
d'oh! rise and fall - was thinking twice as fast as I should have been.... no this is fine. Had a fun audio rate freakfest here a short while ago and was just fine with the range I was getting.
But - I'm glad you asked that: on the dual board, is there some pcb drawing somewhere that correlates the resistor numbers with the values (and other components)? - like I was maybe going to play with the cycle modes, but am not sure what is what on the dual board when component numbers are referred to.
I used 1.2k for the locations I think you're referring to, the ones that say 1k on the screen - not that I'm unhappy with anything about how this thing is acting, but should I maybe change those to 1.5k?
That's cool on the roman self start thing, would be in to checking that out.

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Post by toppobrillo » Sun Nov 04, 2012 2:48 am

right the 1K* spots- 1.2 to 1.5K is OK, I went 1.5 on my newest boards, just increases the control range to about what It whould be,, the actual ideal value would be around 1.35K i think- you should be able to trim it for 1mS at min and around 10S slope at max [w no CV in] I dont thnk I ever posted a ref. designator picture of the board, as it really doesnt have any perse, but the ones w the asterisks are the ones..

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Post by lessavyfav » Mon Nov 05, 2012 12:34 pm

bSmith - I'm stuffing boards this week. Thanks for blazing the trail. and to toppo for the feedback.

Also, doing a dual power supply kit so I can stop crossing my fingers while testing + debugging plugged directly into on my 9u :eurosmoke:

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Post by lessavyfav » Mon Nov 05, 2012 1:14 pm

Hey Yall, I realized that I don't have the mpf102. I looked online and found someone recommending bf245 Bs or Cs but that the pinout in inverted so they must go in "backwards" apparently "bf245 B or C will bias near the mpf102"

I am gonna try the "B" I guess, unless someone knows better (technically almost anyone knows better)
http://www.mouser.com/Search/ProductDet ... 512-BF245B

reference to the quote:
http://www.diystompboxes.com/smfforum/i ... ic=48333.0

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Post by bsmith » Mon Nov 05, 2012 6:16 pm

got my mpf102's at ratshack, looks like it's generally stocked in their stores..

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textual
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Post by textual » Mon Nov 05, 2012 9:23 pm

lessavyfav wrote:Hey Yall, I realized that I don't have the mpf102. I looked online and found someone recommending bf245 Bs or Cs but that the pinout in inverted so they must go in "backwards" apparently "bf245 B or C will bias near the mpf102"
I've got an MPF102 I can give you if you want. I'm in NYC as well. AND pretty sure If you have any relation to the band that is your handle, we played together roughly 10 years ago.. anyhoo let me know if you would like the 102, or I imagine its easy enough to find one via order.

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Post by demian » Tue Nov 06, 2012 4:26 pm

What diodes must be used? I cannot find it except for the two 5240 zenerdiodes..

And what about "A" and "B" ?

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Post by bsmith » Tue Nov 06, 2012 4:31 pm

demian wrote:What diodes must be used? I cannot find it except for the two 5240 zenerdiodes..

And what about "A" and "B" ?
1N914 or 1N418 for the non-zener's - A and B you must mean the trimmers? 50k trim is what I have on mine I just did. I referred mostly to http://www.sdiy.org/toppobrillo/DOWNLOA ... M%20V3.pdf which was for the previous itereation of single channel boards with a few little changes...

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Post by demian » Tue Nov 06, 2012 4:38 pm

Thanks!

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Post by falafelbiels » Tue Nov 06, 2012 7:09 pm

demian wrote:What diodes must be used? I cannot find it except for the two 5240 zenerdiodes..

And what about "A" and "B" ?
Are you actually building something Demian?

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Post by lessavyfav » Tue Nov 06, 2012 7:24 pm

Textual- yes that is me. I will pm you for details about our history together!
I'm Tim and I'm excited for modular synthesis! :nana:

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Post by demian » Tue Nov 06, 2012 7:28 pm

falafelbiels wrote:
demian wrote:What diodes must be used? I cannot find it except for the two 5240 zenerdiodes..

And what about "A" and "B" ?
Are you actually building something Demian?
Ofcourse not, you know me..! :mrgreen:

I am making a list of components to order so i can start building when i am ready for it.. :hihi:

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Post by falafelbiels » Tue Nov 06, 2012 7:54 pm

Don't back out! Not even during the complicated and tedious wiring job that this module will present you! The module when finished is quite the reward.

Remember MASK has your back...

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Post by hpsounds » Fri Nov 09, 2012 9:39 pm

Is the BOM at the top of this topic for 1 or 2 PCBs ?

:hmm:

Hédi K.

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bsmith
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Post by bsmith » Fri Nov 09, 2012 9:44 pm

def looking like dual bom to me - ie for 1 dual channel board (I see 10 x 49.9k resistors, 1 x LM13700, etc...).

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Post by rowman » Fri Nov 09, 2012 11:09 pm

Yeah you need to double it to build a quad module.

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Post by hpsounds » Fri Nov 09, 2012 11:40 pm

Thanks. That's what I was thinking too, but I've counted 32 47K resistors for each PCB and there is 40 x 47K in the BOM. :hmm:

Hédi K.

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