ARP Odyssey Oscillators

isak · Posted: Tue Sep 11, 2012 9:41 am Post subject:

thanks AndyR1960 for this cool share!

can i use 2N5457 for 2N5459?
as i see in the datasheet when searching for 2N5459 the 2N5457 is there as well.
http://www.fairchildsemi.com/ds/2N/2N5459.pdf
i have 20 of them.

cheers,
Isak E.

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

Ive just built 2 boards with this latest BOM/PCB, and i have some issues.
The VCO is VERY high pitched, and dont react much at all to the scaling, no matter how much i turn the Trimmers.

I have checked the resistor colorcodes twice, they all check out. I have even measured with a multimeter the extra resistors i had from this build (i always buy som extras of everything i build) and they all show the correct values.

Also, for the VCO-board im troubleshooting, i have put a jumper between the 150k and 100k Sync pads, as its meant to be the master VCO.

I have gone by the BOM for everything, but still this happens. No idea what can be wrong here.

Capacitors:
680pF Polystyrene - http://se.mouser.com/Search/ProductDetail.aspx?R=23PS168virtualkey21980000virtualkey23PS168
1n - http://www.electrokit.com/pc12-1-nf-50v-poly-5mm.42812
10n - http://www.electrokit.com/mks2-10nf-63v-5mm.42821
100n - http://www.electrokit.com/mks2-100nf-63v-5mm.42658

Ive seen people having problems from time to time with the 4011, so its worth mentioning that i use the CD4011BE.

From Andys pic, i noticed his trimmers are the oposite way around from the BOM, not sure that could mean anything tho.. havent tried that yet.

I really cant figure this out.. Any ideas on what to try?

isak · Posted: Wed Sep 12, 2012 1:34 am Post subject:

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

Anyone?

Sebo · Joined: Apr 27, 2007 Posts: 564 Location: Argentina

isak · Posted: Wed Sep 12, 2012 10:20 am Post subject:

Thank for replying Sebo.

Can you tell me please if I can use 2N5457 instead of 2N5459?
I'm not that expirenced on reading datasheets Embarassed

Thanks in advance,
Isak E.

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

Have anyone actually followed this last BOM and built a working version? (perhaps theres something missing, misplaced, forgotten like the 3.3M resistor for example)
I cant find anything wrong in my build, everything checks out.
Still wont work however.

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

How important are the resistor values?
I mean, i noticed during my troubleshooting that i had a few that wasnt spot on.

91k instead of 88.7k
12.1k instead of 12k.
219k instead of 221k
472k instead of 475k

I presumed they were close enough, but as i really cant find anything else that might be wrong in this build, im reaching for anything.

Also, what kind of voltage would the trace between the tempco and 475k, 49.9k be at? My measure around that part seems a bit odd.

Anyone? Please?

isak · Posted: Wed Sep 19, 2012 9:07 am Post subject:

you said you build 2 boards, does the problem is in both boards?
did you use the same components on both boards?

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

isak · Posted: Wed Sep 19, 2012 9:30 am Post subject:

You know...when I think about it i think no One built the single board version.
I think they all built the dual board version.
If you can...try building the dual board version with the same components and if you'll get the same problem with dual version something is wrong with your components, if it works then something wrong with the single board version.
What do you say?

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

Sebo · Joined: Apr 27, 2007 Posts: 564 Location: Argentina

Hi:
Frequency Central is selling boards of the single ARP VCO based on this layout.
http://www.muffwiggler.com/forum/topic-65782.html
I think he build one, and there is a lot of people there building it.

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

isak · Posted: Wed Sep 19, 2012 11:26 am Post subject:

That's good news, I really looking foreword to see if you solve the problem!
Wating for updates!!!

isak · Posted: Thu Sep 20, 2012 2:48 pm Post subject:

Have a noob Q about this vco design..
Can it output the saw and the square simulteneouly like in the sh101?

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

isak · Posted: Fri Sep 21, 2012 1:25 am Post subject:

i really really want to build it!!!!
you know, i'll be adding this cool Saw to TRI - SINE as well Smile

http://hem.bredband.net/bersyn/VCO/Saw%20to%20tri-sin%20W.gif
http://hem.bredband.net/bersyn/VCO/Saw2tri-sine_L.pdf
http://hem.bredband.net/bersyn/VCO/Saw2tri-sine_K.pdf

i hope they will work good together Question

isak · Posted: Fri Sep 21, 2012 5:06 am Post subject:

as i understand i have only 2 CV inputs.
1 for the 1v/Oct Kbd.
the other is free to use.
if i want more cv inputs can i connect it like i did in the pic?
(red lines, blue resistor)

thanks.

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steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

I dont see why that wouldnt work.
However, when you look at Andys dual VCO version, he put the other FM input elsewhere - see pic.

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isak · Posted: Sat Sep 22, 2012 3:16 am Post subject:

if you look closely you will see the dual ver and the single ver FM outputs are from the same spot Wink

now i know it will work Smile

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

On my quest of troubleshooting this, i wonder..
For the 1nF, i used these:
http://www.polytrade.com.hk/up_product/PC12.pdf

Instead of the "recommended" MKS ones.

I have a bunch of these at home:
http://www.wima.com/EN/WIMA_FKP_2.pdf

Worth trying, or wouldnt it make any difference in the end?

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

A mate of mine just gave me something to think about.
I got carried away here, thinking a Eurorack version meant 12v, but now after looking around here, i dont see anything like that mentioned. This might explain my stuck on high pitch issue.

So AndyR1960, do this really work on 12v, as eurorack usually do?

steffensen · Joined: Jul 11, 2012 Posts: 103 Location: Sweden

Not sure why i keep posting here, this thread seems to be pretty abandoned..

However, just wanted to update my effort of getting this thing to work on 12V. I managed to get the pitch down from the 2khz droning it was stuck on.
Now its lowest is at around 120hz instead, which is a lot easier on the ear heh.. (still not low enough tho imo)

I swapped the 2N3906 that i used instead of the 2N5910. Used a 2N4125 instead, and that worked a lot better.

It still wont track that good tho, its half a octave off more or less.

Tried swapping the 680pF with higher and lower values. 1000pF tracked a bit better actually (and lower in pitch - nice), but it still was off by at least 1/3 of a octave or so..
I even tried 6800pF, and that went really low. Razz

Same tracking as with the 1000pF value tho.

I have a bunch of resistor to swap next, just hoping that someone might give some more ideas on what else to try/look for?

isak · Posted: Fri Oct 26, 2012 12:40 pm Post subject:

Hi man

Happy to hear your getting somewhere, hope you'll fix this thing soon!
Actually I'm following your progress, I've not abendoed you Wink

PMed you