Showing posts with label DIY. Show all posts
Showing posts with label DIY. Show all posts

Wednesday, 12 July 2017

NLC Plague of Demons

Plague of Diamonds Eurorack module build notes.

Checkout electronotes EN #75.

It's a thru zero VCO that uses analogue switches (DG202) rather than FW rectifiers.
Should be easy to use; LEDs indicate when it crosses zero. 


My understanding of the through-zero concept is that with a regular VCO, if the frequency modulation reaches or goes below 0, you won't hear anything. With a thru zero VCO, you'll hear "negative" frequencies.  

"The negative-frequency version of a waveform is simply a time-reversed replica of the original waveform". (Ian Fritz. 2009)
Check out Dave Brown's scope shots on his site (Modularsynthesis.com)
of the Ian Fritz "teezer" Thru-Zero VCO
They explain the concept so well.
The BOM requires:
a S1JL rectifier
Mouser No: 821-S1JL

and a JFET
Mouser No: 512-MMBFJ108

Both have a long backorder wait at mouser.
So possible replacements are:
mouser no: 771-PMBFJ108-T/R for the JFET
and
Mouser Part No: 583-FM4005-T for the recitfier.
The rectifier is polarized. The cathode end is marked with a band. 

This replacement is slightly too big for the PCB. so i had to solder it on its side.
 
On the PCB, I think Andrew has marked the cathode with a dot.

NLC words of wisdom


I like to get the ICs on first.

I'm using PCB version 2, so some mods are needed.
Had to cut one trace and add two resistors (10k & 2.2M).
Be careful not to short anything ... its a bit tricky

Q1. Its a PNP/PNP matched double trannie.
I used a microscope to find the dot that helps orientate it. But if your eyes are better than mine you could do without the scope.

The 1K tempco resistor.


INSTAL headers. theyconnect the two PCBs.









Links
* NLC Blog
* Build notes
* Electro-music (Ian Fritz)
* Modularsynthesis.com
* mUFFwiggler


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Tuesday, 11 July 2017

NLC 32:1 - build notes

This is a Driscoll/Warren Burt inspired Eurorack module.

I am lucky to have the original Driscoll module on which this is based
so am keen to compare the two.

 The 32:1 can split 1 input into 32 outputs or vice versa.

This uses two CMOS analog multiplexers.
Mouser Part No:
A multiplexer is a device that can select from several different input signals
and transmit either one or more output signals
The DG506B is a 16-channel single-ended analog multiplexer designed to
connect one of sixteen inputs to a common output as
determined by a 4-bit binary address (A0, A1, A2, A3).



It also uses two CMOS up/down counters.
Mouser Part No:

 The CD4029 is a presettable up/down counter which counts in either binary or decade mode depending on the voltage level applied at binary/decade input.
When binary/decade is at logical ``1'', the counter counts in binary, otherwise it counts in decade. Similarly, the counter counts up when the up/down input is at logical ``1'' and vice versa.

The inputs consist of a clock (15), Carry In (5), Binary Decade (9), UpDown(10), Preset Enable(1)
and 4 individual jam signals.
The outputs : Q1,Q2,Q3,Q4 and a Carry Out (7).

 Some NLC words of wisdom.
PCB 1.
I accidently removed a trace from thr PCB connecting to one of the multiplexers. Thus the addition of that green wire.

The second mistake I made was adding the jacks before putting on the headers.


I used 1K LED resistors

"The LEDs count in binary, so just 5 of them...rather than 32".
I'm guessing they count from Zero to 31 ??
Decimal "32" is Binary "100000".................to display this would require 6 LEDs
 To convert decimal 32 to binary is easy as 32 is already in the table.


I just confirmed with Andrew F that the module does indeed count from 0-31.
"As the old joke goes : There are 10 kinds of people. Those who read binary, and those who don't"


Links
* Build notes & BOM
* NLC Blog
* MUFFs
* Youtube
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You can find more NLC builds here.
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Thursday, 6 July 2017

Serge Positive Slew - Paperface - restoration

Some pics of the Positive Slew.
This is from panel 2.1 (Warren Burt paperface).

 The red IC socket holds a LM3900 opamp which I swapped.
No improvement though. :-(
The module is powered by -12V (bottom blue), +6V (Green), +12V (Red), 0V (Blue top)

Connecting the lower pulse output to START or SUSTAIN should cause the Positive Slew to operate as a VCO or LFO..




The module uses two OpAmp ICs:
a  LM3900 & a MC 3401


The above pin out is for the MC 3401 operational amplifier.
The Motorolar MC3401, is out of production.
It seems to be responsible for providing both pulse outputs .
The lower pulse output exits pin 9.
The upper exits via pin 10
It seems that the Opamp is being used as a Schmitt trigger circuit with positive feedback.
The Schmitt trigger will convert any regular or irregular waveform into a pulse or square wave.
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The LM 3900 is used extensively throughout the serge modules... in this circuit its used in a negative feedback config. 
It's interesting that both Quad op amps have identical pinouts.
I wonder if we can swap the MC3401 for LM3900s . My next question is why Serge chose
to use the MC3401s in the first place.
Another possible substitute for the MC3401 could be the CA3401 ???




This style of banana socket are I think impossible to remove without breaking them.
A post shared by jono (@dj_jondent) on




To be continued.


Links:
1. Ken Stones CGS - Positive Slew
2. DUSG - CGS 
3. Serge.synth.net
4. Tim Stinchcombe

Serge Restoration Paperface 2.1

This is the upper panel from box 2

This contains:
  • Dual Positive Slew
  • Dual Negative Slew
  • 2 Smooth and Stepped Function Generators
  • 1 Dual VC Slew Generator
  • 1 Peak and Trough 
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 The lower module is the negative slew
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