Transistor matcher (AMORE)

The prototype version of the board. There are a few differences compared to the final board.

For many of the AMORE modules you need matched transistor pairs. You can of course buy expensive matched transistor pairs but with this simple tool you can instead match pairs of inexpensive standard transistors.
The AMORE Transistor Matcher is based on a method devised by fellow synth-DIYer Ian Fritz. You should read all about the testing methodology in his documentation.

This module only uses the supply voltages from the AMORE connector. But by designing it as a regular AMORE module, you can just plug it into the AMORE Starter Kit when you need to match transistors.
The Transistor matcher module has sockets for both NPN and PNP transistors. You plug in two transistors at a time and measure the voltage difference (see Ian Fritz' instructions). The transistor pairs use the three rightmost holes in the 14 pin IC sockets. In the eight holes to the left, you can plug in the transistor pair / tempco modules that are used in the Bergfotron VCOs. So you can check the matching of these and also to check whether they are OK or defect. Note that you shouldn't plug in both the module and discrete transistors simultaneously.
To the right of the NPN/PNP sockets there is a socket for checking FETs. This socket is intended for plugging in just one FET. So you can't check the matching between two FETs, it only shows whether they work or not. This can be useful, as the MOSFETs are easily damaged from static electricity. The FET socket is made of a PCB header socket strip, sawed to the desired length.

Measuring NPN or PNP transistor pairs

Plug a digital millivoltmeter into the banana sockets. Use the right section. The left is for NPN transistors and the right for PNP. Each section has it's own sockets.
Toggle the arm of the SPDT switch forward. This turns the section off.
Plug the transistors in the sockets with the collectors to the left and the bases in the middle. Touch the transistors as little as possible, to prevent them being heated by the fingers.
Toggle the arm of the SPDT switch back. This turns the section on.
Read the voltage. It will drift at first and then slowly stabilize
Flip the DPDT switch and read the voltage again.
Adjust the multiturn trimmer and flip the switch again.
Do a new reading. If the difference has decreased, reiterate until there is no difference when you flip the switch. If the difference increases, turn the trimmer in the opposite direction.
When there is no voltage change when flipping the switch, you can leave the trimmer in that setting and don't have to retrim it when switching transistors. Naturally, you'll have to trim both the NPN and PNP sections the same way.
The remaining voltage reading is the transistor mismatch. Note it down.
Toggle the arm of the SPDT switch forward and swap one of the transistors, unless the difference is less than 0.5 mV. In which case you swap both transistors because you have a matched pair that you can solder into your module and use.
Toggle the arm of the SPDT switch back and remeasure with a new transistor.
Repeat until you have enough matched pairs.

Checking FETs

Plug a FET into the socket with the source to the left and the drain to the right. Note that MOSFETs are sensitive to static electricity so touch them only by the black plastic part.
Turn the trimpot with a screwdriver and observe the LED. If the FET is OK, the LED should come on and go off when you turn the trimmer.

Bill of materials

You should have access to the parts in the general bill of materials.
In addition, you need the following parts:

100 kohm resistors with 0.1% tolerance (4)
DPDT toggle switches (2)
SPDT toggle switches (2)
LED (1)
Banana jacks (4).
PCB header connector strip

The transistor matcher with an NPN module, a PNP pair and a MOSFET plugged in.

Trimming

See above.

Skill level required: LOW

This module has very few parts.

Circuit board layout

Component placement