Construction Notes

(Note: some of the lead spacing issues have been corrected in V1.1 of the circuitboard)

Zener test circuit at bottom of this page.

Please read the First Things First section before starting your kit.

On some capacitors it is important to carefully bend capacitor leads to fit easily into holes. If you force leads not formed, you may break lead off capacitor body. Because of various manufacturers, the lead spacing may vary greatly. The picture below shows leads of a preformed capacitor (left) from manufacturer, and leads that will be bent by you (right).


Hint: If you don't have access to a good magnifying glass and have a smartphone, use your smartphone camera to take a picture of the small printing and zoom in to magnify just like the picture above and below.

When the capacitor is mounted it should look like this:

D1 - 1SV149 orientation. Must be installed as shown below.

R24 - 500 ohm potentiometer lead spacing

Some pots that come with the kits may not have the lead spacing that the board is laid out for. You will need to bend the wiper pin (right pin in picture) slightly with needle nose pliers as shown and straighten the other two leads and bend the two left pins slightly towards the center.

Care should be taken when installing R24 pot on the board. Make sure the center wiper lead makes it into the hole/pad. You may have to wiggle it and help the lead into board with a small screwdriver. The pins should just make it through the board. Instead of a special tool, you can use your fingernail to make adjustments.

Insert pot on board and make sure its straight like the picture below and solder.

Diode D11 and D12 (if used) are identified as follows:

D11 (1N5236 7.5V zener) has a silver body as of this run of parts.

Caution must be noted on the 7.5 volt and 33 volt zeners. They could be clear glass type like the 1N4148 or they may have a silver coating on the case. Some batches have case coatings reversed. In any case, use a magnifying glass to verify the correct numbers. 1N5236 7.5 V, 1N5257 33V.

D12 (1N5257 33V zener) has a glass body and looks like a 1N4148. Do not mix them up!
D12 comes in a bag with D11 and separate from other diodes.


Closeup view of RG174 soldered to board.
As of this board run you may have to remove a few strands of braid to get it to insert into board.

Rear panel power connector wiring.
Center pin is +12 volts!

5.5 x 2.1mm coaxial power connector

CAUTION: If using a transformer "wall wart", make sure it is regulated. Most just have a rectifier and capacitor inside and the voltage can be as high as 17 volts even if marked as 12 volts. The newer switching supply wall warts are closer to 12 volts but note that it may generate noise that could appear on the receiver.

Some components will have tape holding the leads together. These parts are normally used in automated insertion equipment. The leads are long enough that you can just cut the leads close to the tape rather than pulling tape off. Some of the adhesive may remain on lead ends and inhibit a good solder joint if adhesive gets stuck in the through hole.

Headphone jack

You must decide what type of earphones or headphones you will use. The most common is a stereo type MP3 earbuds or Walkman type earphones. Stereo plugs will have a tip, ring, and sleeve or 3-circuit plug. If this is your case just tie the tip and ring together going to J3 Pin 2. Just remember that if you plug a mono 2-circuit plug into this jack it will short the output to ground.

Key Jack

For the key jack tie the ground to chassis and the tip to the key circuit

Modular Headers

Your kit includes pins for the modular connector housing should you decide not to wire directly board.


If you decide to use header connectors instead of wiring directly to board, follow the instructions below.

Strip wires as shown above. If you are fortunate to have a good crimper, set the pin as shown.


The above shows a good crimp.


I you do not have a crimper you can carefully solder wire to pin. Strip wire and place in pin as shown above.


Carefully fold portion of pin around stripped wire.


Carefully dab solder over the crimp. Too much heat will cause solder flow throughout the pin rendering it useless.


Using needlenose carefully roll the part of the pin around insulation. Be sure to roll it tight otherwise it will not fit into the housing.


Push pinned wire into housing with solder side up and holes in housing up. They should snap in.
If you need to remove a wire you can insert a sharp blade to release the latch on top of housing and pull wire out.

Using a knife or Xacto blade carefully scrape enamel insulation about a quarter inch from the toroid body.
No need to scrape the whole length.
You can leave the wire leads long to ease inserting them into holes.

Cheap and dirty Zener tester

If you happen to mix the two Zeners up or can't read the values you can lash up a quick way to verify which one is the correct one. If you mix them up it may be a messy job swapping them because you could damage the board or destroy the fragile Zeners so make sure you test them if you cannot read them.

You could snap two 9 volt batteries or use a variable power supply for the power source. The volt meter will show the Zener breakdown voltage.

Without the Zener in place the meter must display the voltage of the power source. Inserting the Zener will drop the displayed voltage to the Zener breakdown voltage.

Remember, there are two Zeners in the ME+ kits, 7.5v and 33v,  except for the ME20+ which has only one 7.5 volt Zener.

So it's only necessary to identify the 7.5 volt Zener.