Buchla 100 system diy build

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APETECHNOLOGY
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Post by APETECHNOLOGY » Wed Apr 25, 2018 1:56 am

moogboy010 your din0-shots look great!
i need to get my 140 built, but first...

on 2 of my 158's when i "morph" from sine to saw i get a significant increase in amplitude and transient spikes. any ideas what would cause this?

:cry:


ImageImage :cry:

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Post by Jarno » Wed May 23, 2018 4:56 pm

Progress on the 144 oscillator...
I have boards in, and everything seems to work
Image

The range was ear-piercingly high with the 2n2 timing cap though, after a few iterations I am now up to about 24n7 (2n7 and a 22n tacked in parallel). Still cannot get any lower than about 280Hz, definitely not down to 5Hz.
I am using a 2n3904 matched pair and a 2N5460 FET, and on 15V.

Need to do some more prodding.

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Post by moogboy010 » Wed May 23, 2018 7:53 pm

Your board looks' very nice,Jarno! I would try a (J175). It might work better than the (2N5460)? I was able to make a couple of (J175s') work in range.
Good luck.

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Post by Peake » Thu May 24, 2018 12:12 am

Jarno, if your design is a 100% clone of the original, know there's one mistake in the schematic which results in what you're describing, being stuck out of audible range. The connection to +15 at Q2's collector should not exist.

https://rubidium.dyndns.org/~magnus/syn ... _1_200.jpg
I just can't help imagining that this would be better with vactrols

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Post by Jarno » Thu May 24, 2018 4:57 am

Yes, that's a well known error in that schematic, so in my PCB that connection is not there.
It seems to respond well, it is just that the range is a lot higher than expected. Could be because of the transistors (and their properties) used in the diff pair.

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Post by moogboy010 » Thu May 24, 2018 9:52 am

I would try another (P-Channel JFET).Some seem to work(in-range)better than others'?

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Post by Peake » Thu May 24, 2018 12:19 pm

The IT122 dif pair specified for the 144 (and 110, 111, etc.) is easily available and is inexpensive. I don't see on your PCB where a dual pair package would go so check the characteristics of the IT and find discrete transistors which match...
I just can't help imagining that this would be better with vactrols

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Post by Jarno » Thu May 24, 2018 4:09 pm

Ah, didn't realise one could still get IT122, I figured it was one more unobtainium part.

Well, put in a lower gain for the two first transistors (realised they are not connected like a diff pair). I used MPSA42. That seems to help, I have 2N3820 in there for the FET, sort of the same result.
I tacked 100nF over the 2n7 timing cap, range is now much lower :)

It's a nice VCO, keen on finding out what they sound like if you have a bunch of them and crossmodulate.
The saw output is also very worthwhile.

Thanks all for the help, I'll plug away at this board for a bit longer, think I will build another 2-3.

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Post by moogboy010 » Thu May 24, 2018 7:12 pm

Glad to hear you are getting the 144 working,Jarno!
Very cool that you are getting some other( P-Channel JFETs) to work in a 144.

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Post by Jarno » Sat May 26, 2018 4:02 pm

Yeah, but I do want to try the IT122 part. Nearly done stuffing another 2 boards.
Peake, I checked eBay, but there are not a lot of them around did you try to get them from China, or from Linear Systems? The ones from China seem a bit fishy, why would they still have NOS parts while they were originally made in the US?

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Post by APETECHNOLOGY » Sat May 26, 2018 5:15 pm

Jarno,
best to buy it122 directly from linear systems.
your board looks great! well done.
:tu:

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regarding IT122

Post by moogboy010 » Sat Jun 02, 2018 2:33 pm

:woah: I have looked at the linear systems' site and it does' not look like they carry the (IT122),unless they have renamed it?I did get a pair from China and they checked-out O.K..
One was a lot hotter than the other one(hfe290)and (hfe750)?
They were packed wel and marked (Intersil/Harris).Took a while to get them and I really didn't need them,but wondered if they were for real?
Vendor: UTsource/China

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Post by Jarno » Sat Jun 02, 2018 3:53 pm

The IT122 can be found at shop.micross.com, search for it122 (can't seem to link directly). Those are the linear systems ones.

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Post by APETECHNOLOGY » Sat Jun 02, 2018 7:39 pm

or in the USA just call them
Linear Systems
Phone: 510-490-9160
i have found this is the easiest way!
+ when they put you on hold there is old school electronic music!

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Post by moogboy010 » Sat Jun 02, 2018 7:53 pm

Thanks' for the tel#,Apetechnology!Very Cool!

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Post by APETECHNOLOGY » Fri Jul 06, 2018 12:37 am

i did a layout for the 140 and 180 both work!
i will post the pcb art and build info for both after i get them in real panels.
and verify them in use.
the one issue i have is on the 140 in single pulse, i would like to use a 2 pin momentary push button.
not a spdt push button.
any ideas?










ImageImage :despair: :despair:

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140

Post by moogboy010 » Fri Jul 06, 2018 9:49 am

Awesome build,Apetechnology!The (three-way-switch),for (single-pulse),just about has to be a (three-way),unless you want to build a (relay-triggered) by a (two-way-switch).Could be done,but more (room and modification) to the already(difficult-schematic!)Ha!
Great work! :yay: :hail:

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Post by Peake » Fri Jul 06, 2018 3:09 pm

Fantastic news! I should finish my Dave Brown modified 123 which now works...
I just can't help imagining that this would be better with vactrols

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123 mod?

Post by moogboy010 » Fri Jul 06, 2018 3:16 pm

What made the 123 work?Would be interested in knowing the details'?

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Post by Peake » Fri Jul 06, 2018 10:08 pm

I'm not entirely clear but there was apparently interference due to my novice layout which some additional parts and tweaking of parts values solved.
I just can't help imagining that this would be better with vactrols

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123

Post by moogboy010 » Fri Jul 06, 2018 11:55 pm

Hi Peake. Many thanks' to you,Dave Brown and others' who have worked on the 123.
It would really be nice to have a working-modal of that module! :yay: :hail:

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Post by cygmu » Sat Jul 07, 2018 12:29 am

For the pushbutton on the 140, could you do this:

One pin of the button goes direct to the tantalum cap C4, with a large resistor (100k?) also connected there going to 0V.
The other pin goes through a resistor (4.1k I guess) to 15V.

The large resistor is supposed to pull the voltage down when the button is not connected, to mimic the effect of the switch being on 0V. It needs to be big so that the 15V "on" voltage is not divided down too much.

I don't know if this will work. Maybe it won't discharge the cap as fast as you want when the switch is off. Worth a try?

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Post by APETECHNOLOGY » Sat Jul 07, 2018 12:40 am

Dave brown suggested this circuit, i built it on perf boards quick style, did not work :confused:
i built it in a rush,maybe i made a mistake. i need to verify my layout works as designed, with a spdt momentary first .
if i cannot get Daves suggestion to work,i will give your suggestion a try.
thanks! :tu:
cygmu wrote:For the pushbutton on the 140, could you do this:

One pin of the button goes direct to the tantalum cap C4, with a large resistor (100k?) also connected there going to 0V.
The other pin goes through a resistor (4.1k I guess) to 15V.

The large resistor is supposed to pull the voltage down when the button is not connected, to mimic the effect of the switch being on 0V. It needs to be big so that the 15V "on" voltage is not divided down too much.

I don't know if this will work. Maybe it won't discharge the cap as fast as you want when the switch is off. Worth a try?
Image

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Post by APETECHNOLOGY » Sat Jul 07, 2018 12:57 am

great news Peake regarding your 123! :guinness:
i look forward to building one in the future!
for now,looks like i am going the cgs/Djangosfire route.
pretty deep in at this point! :mrgreen:
Image


:lol:

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123

Post by moogboy010 » Sat Jul 07, 2018 8:32 am

Wow,Apetechnology,great work!Love the panels!Amazing layout of boards'! :yay: :hail:
You could also try a (CD4066) as a switch,But then again,more room on an already crowded board?

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