PCBs for Thomas Henry's X-4046 VCO

LektroiD · Posted: Thu May 12, 2011 8:27 am Post subject:

What are the best transistors to substitute for the LM394? I'd rather match my own than spend the rest of my life sourcing such rarities.

Also would they need to be thermally coupled? If I replace the LM394 with individual transistors, one would be the wrong orientation for thermal coupling.

marvkaye · Joined: Mar 14, 2011 Posts: 221 Location: Fla

Actually, you can get thermal transfer by twisting both transistors 90 degrees in opposite directions, then leaning them towards each other until their flat faces touch. The picture below is a pair of 2N3904's that I stuck into the same socket that I'd use for an LM394, just to confirm the concept.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

They haven't been trimmed yet, nor do they have the thermal body for the tempco. I figured I'd make a teeny aluminum tab that gets epoxied between the flats and sticks up for the tempco(s). In this case, since the tab is rather small, I figured I'd use a pair of 1K SMD's wired in series, glue one to each side of the tab. It should be a pretty nifty package when it's done.

<Marv>

PS... has anyone started on a MOTM/DotCom panel for this yet? If not I may give it a shot... I came up with a nice one for the MFOS CV/Gate Distributor... I'll post it on the MFOS forum one of these days.

marvkaye · Joined: Mar 14, 2011 Posts: 221 Location: Fla

A quick follow-up to my prior post.... here I've trimmed about 3/16" off the leads, got the faces to match up square, and made a little tab out of a piece of aluminum I cut from a pop can with a pair of scissors... it's a bit on the thin side, so I'll probably do the real one with some 15-20 mil stock. The bottom of the flag is cut to a point to match the faces of the transistors. I'm thinking it oughta work like a charm. Idea

<Marv>

BananaPlug · Posted: Fri May 13, 2011 5:17 am Post subject:

Somewhere in my gear I've seen commercially made S shaped clips for that.

marvkaye · Joined: Mar 14, 2011 Posts: 221 Location: Fla

I'm sure somewhere out there someone has come up with a commercial version of this, but 3904's at a nickel apiece just beg for bending, twisting, and lending themselves to a home-brewed solution. This one's mine. Wink

<Marv>

fonik · Posted: Wed May 18, 2011 12:57 pm Post subject:

i uploaded three eurorack FPDs to my site: one for the dual version i built (32HP), one for a single full featured version (16HP), and one for just the core VCO (8HP):
http://www.modular.fonik.de/Page55.html

Jojjelito · Joined: Jun 27, 2007 Posts: 49 Location: Stockholm, Sweden

Hi Mattias!

The PCBs arrived in the mail today. Vielen Dank!
Time to heat up the soldering iron... Smile

Captain Biscuits · Joined: Jun 11, 2010 Posts: 112 Location: Northampton, UK

Many thanks Matthias

A pair of very smart red and silver pcbs arrived in the UK today too.

Looking forward to collecting the bits together and getting them made up soon.

Thanks too for the super quick delivery.

All the best

Ian

brother303 · Joined: Nov 02, 2010 Posts: 139 Location: ruhr-area/germany

Hi Fonik,

just took a quick look on your building docs and some questions came up :

- what`s the function of the connect 1 + 2 trimpots?
- how to adjust the hf-trim?
- how to wire j4 (hard sync)?

Thanks!

Wink

fonik · Posted: Thu May 19, 2011 1:28 am Post subject:

tehskull · Posted: Thu May 19, 2011 8:01 am Post subject:

Hello. Would it be possible to put me down for 2 PCB sets?
Thanks!

fonik · Posted: Thu May 19, 2011 8:14 am Post subject:

check PM (your email is not active)

brother303 · Joined: Nov 02, 2010 Posts: 139 Location: ruhr-area/germany

Hi Fonik,

thanks for reply,useful as always...

Regarding j4/hardsync : I didn`t realize that a JACK is wired up to j4,always thought of a SWITCH... Embarassed

emdot_ambient · Joined: Nov 22, 2009 Posts: 669 Location: Frederick, MD

It's easy to remember:
http://www.youtube.com/watch?v=vfNgtFL8VHw&feature=related

"A" is for "apple"
"J" is for "jack"

... Embarassed

brother303 · Joined: Nov 02, 2010 Posts: 139 Location: ruhr-area/germany

Hi,

rosch · Joined: Oct 03, 2009 Posts: 155 Location: germany

they arrived today!
thank you very much for this project!

brother303 · Joined: Nov 02, 2010 Posts: 139 Location: ruhr-area/germany

Yup,

my pcbs also arrived today. Very Happy

Cheers!

tokyomatik · Posted: Sat May 21, 2011 4:48 am Post subject:

hi mattias
i received the pcbs and i have to say you did a great job.
all the connections for pots and jacks are made just to keep the soldering work fast, easy and clear.

thanx a lot

adambee7 · Joined: Apr 04, 2009 Posts: 420 Location: united kingdom

boards arrived. cheers chap. Very Happy

droffset · Posted: Sat May 21, 2011 10:47 pm Post subject:

Ooh, If there are any left I'd love to get two.

kupfer_m · Joined: Oct 14, 2010 Posts: 47 Location: Belgium

I received my boards too!

arsonus · Joined: Apr 17, 2011 Posts: 14 Location: Slovakia

Boards arrived today!
Thanks a lot!
Very Happy

LektroiD · Posted: Tue May 24, 2011 4:30 am Post subject:

The 3904 matched pair looks great, I'll be using these in conjunction with SMD tempcos (2K/3000ppm), hopefully that'll be close enough to the mark.

Also, how essential is R54? The only 1.5MΩ I have is 5%.

fonik · Posted: Tue May 24, 2011 4:40 am Post subject:

tokyomatik · Posted: Tue May 24, 2011 9:11 am Post subject:

i'm searching for some trimmers but i have only 1/2w for the 100ohms
does it make a lot difference or it should be 1/4w?