Tuesday, 27 June 2017

Serge Paperface Restoration - Warren Burt - 2/2

Finally I'm getting around to fixing the Warren Burt Serge Modular.
I think I purchased this synth back in 2013.
Sorry Warren that its taken so long to get started.

This is the second panel from the second box.

    Panel 2 of Box 2:
  • 1 Dual Positive Slew
  • 1 Dual Negative Slew
  • 2 Envelope Generators
  • 1 Triple Bi-directional Router
  • 1 Triple Comparator
  • 1 Schmitt Trigger 

----The power supply for this panel consists of  +12, -12, +6, & ground

Schmitt Trigger & Triple Comparator

The Blue wire seems to be ground. (marked as "W" on PCB)
The Green is I think +6V (Marked as "Y" on the PCB)
The PCB is labelled R11 

Below are some extra pics I have from a surplus vintage PCB.
Might be of use.



Bi directional router
This is marked as R4 on the PCB.

 Double check the wiring by looking at what the pads are labeled.

In this case, 
The blue wire at the bottom is -12V
Red is +12V
There is no 0V/GND connection to this module.
Envelope Generator. We have 2 of these

The boards are I believe 1st generation ... from 1973


 Double check the wiring by looking at what the pads are labeled.
Y=+ 6V

Blue (near the pots is marked W on the PCB) is ground.
Red (X) = +12V
Green (Y on PCB) = ??? My guess is its +6v.

Below are some pics from an extra Envelope Generator PCB. Its marked R7 so 
is possibly also 1st generation, 1973.
This is not part of the Warren Burt pile but it might help me work things out.
Lovely dark blue colour too.

I think this is a voltage divider circuit to create 6V from 12V.


Negative slew

2. CGS
3. Muffs

The 1973 PCB used +12, +6, -12 & ground.
The 1975 PCB used +/-12 V & ground.
So I'm guessing this is a 1975 PCB  as it uses +/-12 & 0V unless it has a on board 6V regulator.

The upper slew was working.
But not the lower. So i needed to trouble shoot this.
Positive Slew

2. CGS

This module appears to need +/-12V, +6V & ground
 The PCB is labelled R10.
X= +12V
Y= +6V
W= 0V
Z= -12V

Tuesday, 20 June 2017

Multi-Band Distortion - NLC Build notes

These are my build notes for the Nonlinearcircuits Multi Band Distortion module.
It's in Eurorack format.
Andrew has based the layout on a Buchla 194 filter.

This is a fixed 4 channel bandpass from the late 1960's.
He has however added some goodies: Some Fuzz circuits & four Korg 3200 VCAs.
The distorted signal can be mixed with the clean signal . The VCAs use vactrols and allow CV control of the mix.

Andrew's build notes are here:

There are some useful links in the NLC blog:

Some pics of the virgin PCB and faceplate first.

Some NLC words of wisdom:

Jack Smith was born on November 14, 1932 in Columbus, Ohio, USA. He was an actor, known for Flaming Creatures (1963), Chumlum (1964) and Scotch Tape (1963). He died on September 25, 1989 in Manhattan, New York, USA.

I like to get the ICs on first.
Then the rest of the SMDs
Now for the rest of the through hole stuff:
resistors, headers, caps, etc

Vactrols next.
The white dot on the vactrol is the cathode.
On the PCB, the cathode is marked "k"

Jacks & Pots. All B100K
And the faceplate.
Another one done. :-)
You can find more NLC builds here.

Monday, 19 June 2017

Sunday, 18 June 2017

Modular in the (Car)park

So excited about the inaugural Modular in the Car Park.

This will be held on Sunday July 16th, 12noon to 4pm.
The event is open to anyone with a synth.. modular, keyboards, drum machines, etc.
It's undercover so will be held rain, hail, snow or shine.
Please contact me , Andrew, Rory, Claude S,  here, by Facebook or
phone to Prosound & Lighting (02 4226 1177).
Many thanks to Claude Spinelli of Prosound & Lighting for hosting this.

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The address is 16 Flinder's Street Wollongong, 2500

On street carparking & close to North Wollongong Train Station.

The Modular in the Carpark Facebook page is here

Saturday, 17 June 2017

Roland 121 filter & 521

A viewer requested a comparison between the Roland eurorack 521 and the vintage 121.

My understanding is that the  521 filter is not meant to be a clone of the vintage 121m
The docs state it was inspired by both the Roland system 100m and the 700m.
I like the sound of both 521 & 121.
Well done Malekko & Roland.
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The 121 has a lovely bubbly character.
Possibly due to the BA662A OTA (Operational Transconductance Amplifier).
It's actually a VCA chip that Roland also used in the TB303.

The BA662A is long obsolete so I wonder what replacement was used in the 521

 This is from the TB303 service manual.
The OTA is a flexible chip... used in the NLC Dual OTA-VCO
and the Cluster matrix mixer
What the OTA  shares with your common Op-Amp is:
1. a single output.
2. They both have inverting & non-inverting inputs.
3. They both have power lines (V+ & V-)

What makes the OTA different is that it has 2 extra inputs (Ibias & Iabc)
and it's output is a current not a voltage.
So, to put it another way, a OTA is a voltage to current amplifier.

Roland 100m - first pics

Finally .... a Roland 100m.
I loved the Eurorack 521 filter so much I decided to seek out the source.
Many thanks to Mark G.

This is a standard setup ...what Roland refer to as a D-set.
Consists of:

112 Dual VCO, with 3 CV ins, 2 outs, and weak/strong sync
121 Dual VCF, with low-pass and high-pass filters with 24 dB/oct slope
130 Dual VCA with a linear/exponential switch
140 Dual ENV + LFO, (ADSR, invertable, and manual gate button) and LFO (5 waveforms with switchable range: x1, x1/10)
150 Ring Mod, Noise (pink and white), S&H (with lag), and LFO (5 waveforms with switchable range: x1, x1/10)

The 121 VCF is a dual 24 dB Lowpass OTA filter that has Roland's warm, bubbley filter characteristics.

The System 100m offers over 20 modular components to pick and choose to design a custom modular set-up.
There were originally just six modules in the series (released in 1979).
These were the 110, 112, 121, 130, 140, 150.
The 110 was a "voice module" combining a VCO,VCF & VCA in one package.

A further four were released over the next five years (starting in 1980).
These were the
131 (four channel output mixer)  4 X 2 X 1, with panning and a tuning oscillator (220/440/880Hz)
132 Dual CV/audio mixer/ voltage processor.
172 Phaser/gate/delay
182 sequencer

I've read that Roland had plans for a further nine modules but cancelled most of these.
After 1983 they did produce:
160 - Computer interface. (No idea what it does. I saw one for sale in 0ct 2011 so it does exist)

165 - Double Portamento Controller, with CV in
173 - Quadruple Signal Gate and six 4-way Multiples
174 - Parametric Equalizer, four-band, with 20Hz to 20kHz center frequencies.

These appeared just before the company deleted the range.
The cancelled modules were :
111 - VCO/VCF
120 - VCF/VCA
141 - dual envelope, gate delay & inverter/adder
170 - Pitch/Voltage Converter, Envelope Follower, and Audio Amplifer

The System 100m has 3 rack sizes, the M-190 holds 3 modules, the M-191 and M-191J hold 5 modules. Each rack provides the necessary 8-pin DIN power connectors and internal CV/gate connections between the modules
System 100M 8 pin DIN plug connections are as follows:
Pin 1 negative 15 volts....blue
Pin 2 positive 15 volts.....red
Pin 3 LED +22 ???....orange
Pin 4 Gate (NC)
Pin 5 trigger (NC)
Pin 6 LED gnd (NC).....green
Pin 7 PSU/ground.....black
Pin 8 CV ....yellow
This might come in handy if you need to build your own rack

The Roland 181m keyboard also needs to be powered from the case.
Its a similar DIN connector.
Six pins, not eight.

My 184m keyboard has it's own wall plug and internal PS.

This is a 191J  five-module rack with multiple connectors on its base.

Yangon Burma 2016 pics

Yangon served as the capital of Myanmar (Burma) until 2006, when the military government relocated the capital to the purpose-built city of Naypyidaw in central Myanmar. With over 7 million people, Yangon is Myanmar's largest city and is its most important commercial centre.

Yangon boasts the largest number of colonial-era buildings in the region, and has a unique colonial-era urban core that is remarkably intact.

The Sofaer and Co. building in downtown Rangoon was completed by Isaac and Meyer Sofaer in 1906. Both brothers were Baghdad-born.

High tea at the Strand Hotel. Opened in 1901.
It was built by the British entrepreneur John Darwood but later acquired by the Sarkies brothers, who owned a number of luxury hotels in the Far East, including the Raffles Hotel in Singapore and the Eastern & Oriental Hotel in Penang, Malaysia.

 The Myanmar Port Authority.

The colonial-era commercial core is centred around the Sule Pagoda, which reputed to be over 2,000 years old and contains a hair relic of the Gautama Buddha.

 The city is also home to the gilded Shwedagon Pagoda — Myanmar's most sacred Buddhist pagoda.

The mausoleum of the last Mughal Emperor is located in Yangon, where he had been exiled following the Indian Mutiny of 1857.