JonDent - Exploring Electronic Music: Metro-Modular 2102 - Dual Stereo Locator

Friday 24 May 2019

Metro-Modular 2102 - Dual Stereo Locator - build notes

These are some un-official build notes for the Metro Modular 2102 module.
It's in Buchla format.
For more info on this module click here:
https://djjondent.blogspot.com/2019/05/metro-modular-dual-stereo-locator-model.html

The official build notes will be released later.

The virgin PCB and panel

In addition to the main circuit, Justin has added an extra scaler & a JFET tester/matcher circuit at the top of the PCB.
i STARTED building the input scalers section on the top left of the PCB then realised I didn't need it as I was going to install it into my Buchla 100 system.
The whole input scaler section is only needed if you use the module with 10V function generators.
Vintage black knob 100 Buchla is 15V.

I usually start with resistors then add caps.
The resistors I'm using are metal 1%.

Get some 15mm hex standoffs ... female/female.

Yes I agree with Jim. West is Best !

You can also buy a C&K equivalent from Mouser.
You will need to trim the shaft. I'll probably use shears rather than a hacksaw so I don't get grit in the mechanism. yOU ALSO NEED TO RETURN THE SWITCH TO POSITION 1 AND SET THE STOP PIN TO 2.

I'll probably end up soldering the JFETS directly to the PCB, though I have added a socket for the tester.
The JFET matcher is dead easy.
Simply stick the JFET in. and put multimeter probes on the two test points.
Read the voltage.
The voltage should be between 0.7V and 1.2V
The voltage corresponds to the saturation voltage of the JFET
The JFET can be put in back to front (in the test socket only)
The 1k resistor used in this tester must be 1%.

Choosing the JFETs
If you are unfamiliar with JFETS check this link out.
https://djjondent.blogspot.com/2019/05/transistor-families.html

J201s might work, though you will probably need to go through a few to find enough within the correct range.
The bottom two could possibly be PN3819 or J202 ??
2N4339's from mouser are pricey. There is a long waiting period for the PN4339.
How you mount them will depend on the format.
If they are in a T0-92 package they need to be mounted "backwards" .... with centre leg pushed forward..... ie the flat edge of the JFET body faces away from the front..

.....

I ended up buying some tin can 2n4339s on ebay.
Not sure if these are fake ... :-)

These are in a TO-18 package

The input scaler section

This is only needed if you use the module with 10V function generators.
If you are using it with 15V peak black-knob 200 or 100 gear you can ignore it.

If your power supply has +24V just connect the 24V to the rightmost pin of the regulator socket.