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.
----------------------------------------------------------------------------------------------------------------
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 
----------------------------------------------------------------

-------------------------------------------------------------------------------



----------------------------------------------------------------------------------------




-------------------------------------------------------------------------------------------------------



 The lower module is the negative slew
-------------------------------------------------------------------------------------------------------





-----------------------------------------------------------------------------------------------------------


NLC PSU build 2

This is a smaller version of a Nonlinearcircuit PSU I built earlier.
http://djjondent.blogspot.com.au/2017/02/power-supply-nlc-build-notes.html

It uses a 12VAC Wall Wart power adapter.
The AC output of the wall wart is rectified with diodes so that positive voltage gets stored on the caps that serve the positive voltage regulator (LM7812) and negative voltage gets stored on the caps that serve the negative voltage regulator (LM7912).

I'm putting together this PSU for an old Serge modular but its actually for Eurorack.
The serge uses +12, -12, +6 and ground so I will have to add a 6V regulator to this later.

Some pics:


The PCB receives 12VAC from a plugpack/ wallwart
. The 1N4004 diodes split this into positive and negative waveforms.

The 4700uF capacitors then smooth out these waves
. The 7812 and 7912 regulators then convert the rectified & smoothed
signals to +12V DC and -12V DC and these are fed to the connectors to be distributed to your lovely modules.
I'm using 250v TDK film caps for the four small 100nf caps

 Poor Grandma.
Let's Eat Grandma is a British musical group formed in 2013 by childhood friends Rosa Walton and Jenny Hollingworth. 

I decided to use 1K resistors for the LEDs

 Some pics of the additional 6V regulator circuit.
 Using a LM7806
 330nf on the left. 100nf on the right.


Red +12V, Black 0V, White -12V, Green +6V

----------------------
A second build.
I have a very confined case.
 tRYING TO keep everything as flat as possible.



Wednesday, 5 July 2017

Hsinbyume Pagoda - Myanmar (Burma)

This beautiful all white structure on the banks of the Irrawaddy river just North of Mandalay.

 The pagoda that is also known as the Mya Theindan Pagoda.It is located in the Northern part of Mingun town near the massive Mingun Pagoda.


 The all white pagoda was built in 1816 by Prince Bagyidaw.



The structure was dedicated to his first wife, Princess Hsinbyume, which literally translates to White Elephant Princess, who died during child birth. During the large earthquake of 1838 the Hsinbyume Pagoda was severely damaged.





Sunday, 2 July 2017

Paperface Serge - Negative Slew restoration

Serge  Negative Slew restoration.
These are some notes for repairing a old Negative Slew.


The main panel is here
http://djjondent.blogspot.com.au/2017/06/serge-paperface-restoration-warren-burt.html 

The board is marked R9
This is the lower section of the PCB.
The upper section works.
According to Ken Stone's site there are two problems with this.
It's missing one trace and a 4.7k resistor.
I've marked the missing trace in orange.

Also marked the missing 4.7k resistor in orange.

4.7K resistor added.
I removed the 3900 opamp. lots of corrosion in the socket.
Replaced & it works.
:-)
Thanks Ken



Links:
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 module uses two ICs
LM3900. It's a quad op amp

 Ground at pin 7, power is pin 14.

LM3046 
This is a transistor array.
It consists of five general purpose silicon NPN transistors. Two of the transistors are internally connected to form a differentially-connected pair.  



PCB connections:
A = input (1)
B = output (1)
C = VC (1)
D = pulse out (1)
E = input (2)
F = output (2)
G = VC (2)
H = pulse out (2)
U = not used (0v)
W = 0v
X = +12v
Y = +6v
Z = -12v