Instruction manual

SM100 • 11
 6. Install 1N4002 diodes D1 and D2. Notice that the bands do not face in
the same direction when installed.
 7. Install C1, 220 uf electrolytic capacitor. Electrolytic capacitors are
polarized with a (+) and a (-) lead and must be installed in the correct
orientation. Ordinarily, only the negative side is marked on the capacitor
body with a dark band and the (-) sign clearly shown, while PC boards
will usually show the (+) hole location. Use care to ensure proper
polarity. See the parts diagram for proper placement.
 8. In the same manner, install C4, another 220 uF electrolytic. Pay
particular attention to the polarity! In this “voltage doubler” section of the
circuit, installing an electrolytic backwards could cause it to explode!
(We do not suggest that you do this if you have a heart condition, anyone
sleeping in your house or expect a replacement part!)
 9. Identify and install C5, 10 uF electrolytic capacitor. Watch that polarity!
 10. Install R8, 8.2K ohm (grey-red-red).
 11. Install R3, 1K ohm (brown-black-red).
 12. Install R2, 1K ohm (brown-black-red).
 13. Install R7, another 1K ohm (brown-black-red).
 14. Install D3, the 27 volt zener diode (marked 971B). Zener diodes have
a specific reverse “breakdown” voltage (for this diode 27 volts) at which
the diode begins to conduct. We use this property to create a regulated
voltage source at 27 volts. The “TUNE” pot (R6) that you previously
installed will vary the output voltage from 12 volts to 27 volts.
 16. Install LED D4. Being a diode, this component is polarized and must
be oriented correctly. Examine the LED and notice how one lead is
longer than the other. The longer of the two leads is the anode, or (+)
connection. Most diodes also have a flat molded in the component body.
This corresponds to the cathode or (-) side of the part.This flat should
face in the direction of the band marking of the diode. Leave the diodes
leads as long as possible as this component will also mount to the front
panel as a power and tuning indicator.
Notice how the LED is connected to the tunable supply. We could have just
as easily hooked it to the regulated supply, but by using the variable voltage
display, we can also change the intensity of the diode while turning the
“TUNE” knob. How about that for getting your money’s worth out of a part !
 17. Install disc capacitor C3, .01 uF (marked .01 or 103 or 10nF).