Masa921 Micro VCO

andrewF · Posted: Wed Apr 18, 2007 4:48 pm Post subject:

just found this on one of Takeda San's pages -

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

andrewF · Posted: Thu Apr 19, 2007 6:37 am Post subject:

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

I'll re-ordered those now. anyhow, small sum.

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

I still have questions: the capacitors, are those polar or non-polar ?

i've ordered now the missing chips and build the old microvco on breadboard.

andrewF · Posted: Fri Apr 20, 2007 10:10 am Post subject:

Going by Takeda San's schematic - c1, c4, c5, c6 & c8 are electrolytic, so polarised tho it probably doesn't matter if they are bipolar (marked BP) versions.
The 47u caps are for decoupling, you could use a variety of sizes here from 10u to 47u would be fine. make sure the negative side goes to ground.

i notice c9 is unmarked, it looks like it is there to remove the DC offset on the Base input to transistor Q13 - you may have to experiment, i'd try 10n - 100n to start.

with c5 and c8, I would assume the positive side goes to the S-pins on the FETs. Question

(anyone like to confirm this??)

don't be shy to email Takeda San, his address will be on his homepage.
He is a very warm&kind guy and he would be pleased to hear you are trying some of his designs.

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

I spoke with takeda, i have the bom for this circuit now.
however i cannot find Q15 (it's listed in the bom, but not in the layout.

also ... is there a layout for the MASA921 ? i am getting puzzled about the
different layouts of the trannies (sorry, no DIY master).

andrewF · Posted: Thu Apr 26, 2007 4:26 pm Post subject:

Q15 is the 2SJ103, on the schematic near the sync on/off switch

Masa921 built his miniVCO in 3D not on a PCB
there is a photo of it on this thread -
http://electro-music.com/forum/viewtopic.php?highlight=masa921&t=16329
2nd post from the top (mine)
its the blob sitting next to a battery

I think Takeda San was inspired by Masa'a circuit and used the basic concept for his design, don't expect many similarities.

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

andrewF · Posted: Fri Apr 27, 2007 6:10 pm Post subject:

i see what you mean. it looks as though the circuitry around the 2sj103 has been left off between the sync out and sync in connections. also, on the pcb, the saw & sync out labels have been swapped over.

usually it is safest to trust the schematic first, pcb 2nd and BOM last

i guess Takeda San simplified the design for the PCB and just runs the sync in & out connections to sockets. probably best to ask him what he intended.

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

If somebody is interested: I got a fully working and assembled Dual TB VCO Module in front of me as i am cleaning up my storage a bit.
It's just the assembled module.

JRock · Posted: Fri Nov 05, 2010 6:41 pm Post subject:

http://www.aleph.co.jp/~takeda/radio/harvest/img/schem/MS20CloneSet-scheme.gif

I saw this on Motohiko Takeda's Harvestman designs... Would this be for Hz/Oct?

JRock · Posted: Wed Jan 12, 2011 6:49 pm Post subject:

I just got the components in and etched the PCB for the Dual TB VCO. what did you do about Q15? Did the VCO work? What do I need to know from you experienced guys before I build this?

Thanks