AkitikA GT-102 User manual

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GT-102 STEREO
AUDIO POWER AMPLIFIER
ASSEMBLY MANUAL
© 2017 AkitikA LLC
All rights reserved
Revision 1p14 May 13, 2017

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Table of Contents
Table of Contents ................................................................................................................ 2
Table of Figures .................................................................................................................. 3
Section 1: About This Manual ............................................................................................ 5
Who Should Attempt this Project? ................................................................................. 5
Tools You’ll Need........................................................................................................... 5
Project Overview ............................................................................................................ 5
Important Safety Notes ................................................................................................... 6
About Components ......................................................................................................... 6
Recommended Solder ..................................................................................................... 6
Warranty ......................................................................................................................... 6
Section 2: Building the Power Supply PCB ....................................................................... 7
Component Order............................................................................................................ 7
Install the Resistors ......................................................................................................... 7
Install the Diodes ............................................................................................................ 9
Identifying the glass body diodes ............................................................................... 9
Install the Last Resistor ................................................................................................. 11
Install the Small Capacitors .......................................................................................... 11
Install the Integrated Circuits ........................................................................................ 12
Install the Transistors .................................................................................................... 12
Install the Big Capacitors .............................................................................................. 12
Final Inspection of the Circuit Board............................................................................ 13
Power Supply Final Assembly ...................................................................................... 13
Section 3: Assembling the Amplifier Circuit Boards ....................................................... 16
Install the Resistors ....................................................................................................... 17
Install the Small Capacitors and the Diodes ................................................................. 19
Last Capacitors and the Transistors .............................................................................. 20
Winding the Output Inductor ........................................................................................ 22
Install Relay K1 ............................................................................................................ 23
Final Inspection of the Circuit Board............................................................................ 23
Install the LM3866 and Mount the Amplifier Board to the Heatsink........................... 24
Section 4: Wiring it All Together ..................................................................................... 26
Attach the Power Supply Ground Wire ........................................................................ 26
Attach the Amplifier Module Wires ............................................................................. 26
Attaching LEFT Module Wires ................................................................................ 26
Attaching RIGHT Module Wires.............................................................................. 27
Build the Ground Harnesses ......................................................................................... 28
Build the Ground Lifter ................................................................................................ 29
Install the Feet ............................................................................................................... 30
AC Power Wiring ......................................................................................................... 30
Installing Amplifier Modules into the Chassis ......................................................... 32
Install the Speaker Binding Posts ................................................................................. 33
Connect the Speaker Binding Posts .............................................................................. 34
Transformer Preparation ........................................................................................... 35
Transformer Installation............................................................................................ 37

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Testing the Power Supply ............................................................................................. 38
Final Amplifier Wiring ................................................................................................. 39
Wiring Amplifier Power ........................................................................................... 39
Fasten the Power Supply to the Chassis ................................................................... 39
Install the Wall and Fasten the Transformer Down .................................................. 40
Visual Inspection ...................................................................................................... 41
Section 5: Testing It Out and Installing the Top ............................................................... 41
Power-Off Tests ............................................................................................................ 42
Power-On Tests ............................................................................................................. 42
Install the Top ........................................................................................................... 42
Section 6: Using the GT-102 ............................................................................................ 42
Section 7: Specifications and Schematics ......................................................................... 43
Section 8: Theory of Operation ......................................................................................... 47
Power Supply ................................................................................................................ 47
Bulk DC Supply ........................................................................................................ 47
Pass Transistor .......................................................................................................... 47
Regulator Control Circuits and their Power Supply ................................................. 47
Current Limiting ....................................................................................................... 47
Start-up Circuits ........................................................................................................ 48
Amplifier Modules ........................................................................................................ 48
Reference Voltage Generator .................................................................................... 49
Gain Setting Circuits ................................................................................................. 49
Relay Control Circuit .................................................................................................... 49
Appendix 1 - Resistor Color Code .................................................................................... 50
Appendix 2 - Preparing a Shielded Cable End ................................................................. 51
Table of Figures
Figure 1-Component side of power supply PCB before loading ........................................ 7
Figure 2-Installing resistors ................................................................................................ 8
Figure 3-R11 location (PCB's are missing the silk screen for R11) ................................... 9
Figure 4-Form the cathodes of D4-D7 as shown (banded end denotes cathode) ............. 11
Figure 5-Pinout of U1, viewed from the top ..................................................................... 12
Figure 6-Note the rounded brackets used for the power supply heatsink and PCB ......... 13
Figure 7-Placing thermal compound on Q5 ...................................................................... 14
Figure 8-Installing Q5 on the heatsink and to the PCB .................................................... 14
Figure 9-Remember to solder Q5's leads .......................................................................... 14
Figure 10-Assembled Power supply mounted on heat sink .............................................. 15
Figure 11-Component location guide for amplifier PCB's ............................................... 16
Figure 12-Empty the amplifier components into a soup bowl .......................................... 16
Figure 13-Close-up of Amplifier board prior to U1, K1, and L1 installation .................. 17
Figure 14-Four of the same value resistors are installed, leads bent on the back side, then
soldered and clipped. ........................................................................................................ 18
Figure 15-showing LED cathode orientation .................................................................... 20
Figure 16-Starting to wind the output inductor................................................................. 22
Figure 17-finishing step for the output inductor ............................................................... 23
Figure 18-Mounting assembled PCB to heat sink ............................................................ 24

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Figure 19-mounting the PCB to the heat sink ................................................................... 24
Figure 20-Spread a thin film of thermal compound on the LM3886, but keep it off the
leads .................................................................................................................................. 25
Figure 21-a completed amplifier module .......................................................................... 25
Figure 22-from left to right, #6 lug, #10 lug, RCA connector ground lug ....................... 26
Figure 23-power supply with attached ground wire ......................................................... 26
Figure 24-shielded cable for left channel. Right channel has overall length of 11 inches.
........................................................................................................................................... 27
Figure 25-Channel Grounding Harness ............................................................................ 28
Figure 26-Ground Lifter PC Board ................................................................................... 29
Figure 27-Ground Lifter PCB with ground wires connected............................................ 29
Figure 28-Install the feet here ........................................................................................... 30
Figure 29-FASTON connector ......................................................................................... 30
Figure 30-Wiring IEC power connector line and neutral ................................................. 30
Figure 31-Power wiring with IEC connector installed into chassis .................................. 31
Figure 32-Installing power wires on the switch ................................................................ 32
Figure 33-spread thermal compound on the ¼” wide edge .............................................. 32
Figure 34-Installing RCA jacks ........................................................................................ 33
Figure 35-Install both left and right binding posts............................................................ 34
Figure 36-I/O Connector wiring ....................................................................................... 35
Figure 37-Wiring toroidal transformer for 120 Volt operation ........................................ 35
Figure 38-Western Union splice has diameter less than the insulated wires and no sharp
points ................................................................................................................................. 36
Figure 39-connecting up the power transformer ............................................................... 37
Figure 40-Showing active and storage locations in the fuse drawer ................................ 38
Figure 41-Grounding Stud Detail ..................................................................................... 40
Figure 42-Routing the wires thru the slots in the wall ...................................................... 40
Figure 43-Toroidal Transformer Mounting ...................................................................... 41
Figure 44-Power Supply Schematic.................................................................................. 44
Figure 45-Amplifier Module Schematic ........................................................................... 45
Figure 46-Overall Wiring (power transformer is wired for 120 VAC) ............................ 46
Figure 47-demonstrating the resistor color code .............................................................. 50
Figure 48- Shield wire end prep completed ...................................................................... 52

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Section 1: About This Manual
This manual gives the information you need to build Akitika LLC’s GT-102 Stereo
Power Amplifier.
Who Should Attempt this Project?
You can build this kit if you can:
1. solder (using normal rosin core solder and a soldering iron).
2. use simple hand tools like screwdrivers, wire cutters, and pliers.
3. read and follow directions.
It helps if you:
1. know a bit about electronics, or
2. have a friend who knows a bit about electronics
3. can get to YouTube to watch a few helpful videos about the assembly process
Tools You’ll Need
You’ll need the following tools:
1. Phillips screwdriver (#1 and #2)
2. pliers or nut drivers suitable for #6 hardware (5/16” nut driver or hex wrench).
Note that the 5/16” nut driver is also the correct size for the speaker binding post
nuts.
3. needle nose pliers (helpful, but not strictly necessary)
4. pencil type soldering iron of 25 to 50 Watts (no huge honking soldering guns or
blowtorches)
5. wire cutters and strippers
6. multi-meter (strongly recommended to check resistor values!)
7. magnifying glass, if you’re over 42!
Project Overview
The project consists of the following steps:
1. Build the Power Supply Regulator Board
2. Build left and right channel amplifier circuit boards.
3. Install and wire the circuit boards, switches, and connectors into the chassis.

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Important Safety Notes
By purchasing, using, or assembling this kit, you have agreed to hold AkitikA, LLC
harmless for any injuries you may receive in its assembly and/or use. To prevent injuries:
 Wear safety glasses when soldering to prevent eye injuries.
 Always unplug the power before working on the amplifier.
 Large capacitors hold lots of energy for a long time. Before you put your hands
into the amplifier:
o Pull the AC plug!
o Wait 2 full minutes for the capacitors to discharge!
 Remove jewelry and rings from your hands and wrists, or anything that might
dangle into the amplifier.
 If working in the amplifier, keep one hand in your pocket, especially if you’re
near the power supply or power supply wires. This can prevent serious shocks.
 Build with a buddy nearby. If you’ve ignored all the previous advice, they can
dial 911 or get you to the hospital.
About Components
We reserve the right to make design and/or component changes at any time without prior
notification.
Recommended Solder
The kit must be assembled with 60/40 Rosin Core solder. The recommended diameter is
0.032 inches. Among many such sources of solder, I have used Radio Shack part number
64-009. It contains 8 oz. of solder, which is much more than you’ll need to assemble the
GT-102 kit.
Warranty
With the exception of fuses, Akitika will replace for free any parts of a correctly
assembled GT-102 that fail within one year of the date of purchase when the amplifier
has been used in home stereo applications. It is the responsibility of the kit builder to
install the replacement part(s). This warranty applies to the original purchaser only. It
does not apply to units that have been physically or electrically abused, modified without
prior factory authorization, or assembled with other than 60/40 Rosin Core solder.
Akitika LLC’s liability shall in no event exceed the cost paid to Akitika LLC for the kit.

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Section 2: Building the Power Supply PCB
This section details the process of building the power supply circuit board. We start with
an overview on this page. The specifics you need to start building begin on the next page.
The bare power supply PCB is shown in Figure 1.
Figure 1-Component side of power supply PCB before loading
Begin by carefully emptying the contents of the envelope marked “GT-102 PSU Module”
into a broad soup bowl, as shown below. In general, you’ll start with the components that
lay closest to the board, working your way towards the taller components. You will:
1. Install the resistors (all but one
power resistor, left for later)
2. Install the diodes
3. Install the capacitors
4. Install the integrated circuits.
5. Install the transistors
6. Install the pass transistor Q5 as you
mount the PCB to the heat sink.
Component Order
You’ll notice that the component designations in the directions don’t go exactly in order.
We have grouped them so that all components with the same value appear together. This
makes assembly easier. You’ll find in the parts kit that similar parts, e.g. 3 1K resistors,
are typically (though not always) taped together.
Install the Resistors
In general, you install the resistors by placing the body on the silk screen side of the
board, and the leads through the indicated holes. Bend the leads over on the back of the
board to keep the resistors from falling out until your solder them in place. Try to bend
the leads in a direction that won’t lead to solder bridges between traces that should
remain disconnected.

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Figure 2-Installing resistors
We recommend the following procedure:
1. Insert all the resistors of the same value, e.g. R2, R3 and R4.
2. Bend the leads as described above.
3. Solder the leads on the back of the board.
4. Clip the leads.
Track your progress by placing a check-mark in the done column as you install each
resistor. Check resistor values with a meter, and by reading the color code (See
Appendix 1). Orient the resistor with the fat brown band on the right, then you can read
both the Color Code column and the resistor from left to right.
¼ Watt, 1% resistors (if you use a lead-bending jig, use the 0.45” width)
Designation Value Color code Done? ()
R2 1K Brown, Black, Black, Brown, Brown
R3 1K Brown, Black, Black, Brown, Brown
R4 1K Brown, Black, Black, Brown, Brown
R6 10K Brown, Black, Black, Red, Brown
R26 10K Brown, Black, Black, Red, Brown
R27 10K Brown, Black, Black, Red, Brown
R8 20K Red, Black, Black, Red, Brown
R9 20K Red, Black, Black, Red, Brown
R1 15K Brown, Green, Black, Red, Brown
R5 140K Brown, Yellow, Black, Orange, Brown
R7 5K76 Green, Violet, Blue, Brown, Brown
R10 26K1 Red, Blue, Brown, Red, Brown
R11
1
3K48 Orange, Yellow, Gray, Brown, Brown
R13 3M01 Orange, Black, Brown, Yellow, Brown
R22 165K Brown, Blue, Green, Orange, Brown
R23 100 Brown, Black, Black, Black, Brown
R24 95K3 White, Green, Orange, Red, Brown
R25 This location remains empty
We will defer installation of R12, a 0.1 Ohm power resistor, for a bit later in the assembly
process.
1 See next page for location of R11. The R11 designation is missing from the silk-screen.

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Figure 3-R11 location (PCB's are missing the silk screen for R11)
Install the Diodes
Now install the diodes. Be careful to observe the polarity markings on the diodes. You’ll
notice that one end of the diodes has a band. That band indicates the cathode of the diode.
Match the banded end of the diode with the banded end of the silk screen. The following
information should help you identify the diodes.
Identifying the glass body diodes
The glass body diodes have the following identifying marks. If your vision is like mine,
you may need good light and a magnifying glass.
 1N4148, D8-D11, has the number 48 visible
 BZX55B33B, D1 and D14, has the number 33 visible
 BZX79-B10, D2, has the number 10 visible
Also, typically when these diodes are packed, you can preliminarily identify the types
because:
 The 4 1N4148 diodes will typically be taped together
 The 2 BZX55B33B diodes will typically be taped together
 The 1 BZX79-B10 diode will be by itself

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D4-D7, opaque
black plastic
package
D12, D13,
package type
DO-41, opaque
black plastic
package
D1, D2, D8-
D11, D14,
package type
DO-35, glass
package
Keep track of the diodes as you install them using the following table. Remember to
watch the polarity of the diodes, matching the banded end of the diode to the banded end
of the silk screen.
Designation Type, Package Description Done? ()
D1 BZX55B33, DO-35 33 Volt 2% zener diode
D14 BZX55B33, DO-35 33 Volt 2% zener diode
D2 BZX79-B10, DO-35 10 Volt 2% zener diode
D8 1N4148, DO-35 0.2 A, 100 PIV, switching
diode
D9 1N4148, DO-35 0.2 A, 100 PIV, switching
diode
D10 1N4148, DO-35 0.2 A, 100 PIV, switching
diode
D11 1N4148, DO-35 0.2 A, 100 PIV, switching
diode
D12 1N4004, DO-41 1A, 400 PIV, rectifier
diode
D13 1N4004, DO-41 1A, 400 PIV, rectifier
diode
Warning: Don’t cut the leads of D4-D7 until after the leads have been formed and the
diodes have been soldered into the PCB.
Form the leads of D4-D7 as shown in Figure 4. Solder one lead of each diode while
attempting to keep the body perpendicular to the plane of the board. Ideally, the anodes
of D4-D7 should sit about 1/8” to 1/16” off the board.

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Figure 4-Form the cathodes of D4-D7 as shown (banded end denotes cathode)
Designation Type, Package Description Done? ()
D4 6A4, R-6 6A, 400 PIV, rectifier
diode
D5 6A4, R-6 6A, 400 PIV, rectifier
diode
D6 6A4, R-6 6A, 400 PIV, rectifier
diode
D7 6A4, R-6 6A, 400 PIV, rectifier
diode
Install the Last Resistor
R12 should be air-mounted, with the bottom of its body about 1/8” above the PCB.
2 Watt, 5% resistor
Designation Value Marking Done? ()
R12 0.1 0.1
Install the Small Capacitors
Now install the small capacitors:
C1, C2, and C3 are polarized, showing a minus sign (-) on the negative end of the
capacitor. Make sure that the minus sign faces away from the plus sign (+) marked on
the silk screen for each of the capacitors.
Designation Value Description Done? ()
C1 10 µF 100V electrolytic (polarized), cylindrical
shape
C2 10 µF 100V electrolytic (polarized), cylindrical
shape
C3 10 µF 100V electrolytic (polarized), cylindrical
shape
C4 100 nF 50V, Z5U, +/- 20%, marked 104
C5 10 nF 400V, film, 20%, box shaped, marked
10nk400

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Install the Integrated Circuits
Install the integrated circuits.
Orient U1 so that pin 1 on the chip matches pin 1, the square pin, on the PCB.
Orient U2 to match the silk screen outline.
Designation Type Description Done? ()
U1 LM258 or LM358 8 Pin DIP
U2 TL431, TO-92 Programmable shunt regulator
Be careful! Don’t confuse U2 with the transistors. Make sure you see “431” on U2.
Figure 5-Pinout of U1, viewed from the top
Install the Transistors
You may have to spread the outside leads a bit to make it easier to insert them into the
board. Do not install Q5 now. It will be installed later.
Orient the transistor so its body shape matches the silk-screen outline. Leave the top of
the transistor about ½” off the board! The lead length prevents stress on the body and
keeps the transistor safe from too much heat during the soldering operation.
Designation Type Description Done? ()
Q2 2N3904, TO-92 60 V NPN bipolar transistor
Q3 2N3904, TO-92 60 V NPN bipolar transistor
Q4 2N3904, TO-92 60 V NPN bipolar transistor
Q6 2N5401, TO-92 150 V PNP bipolar transistor
Q7 2N5401, TO-92 150 V PNP bipolar transistor
Don’t use too much solder on the transistor leads. This is one place where the spacing is
close enough that extra solder might cause short circuit between two leads on a given
transistor. Note that Q4’s collector and base are connected by the circuit board.
Install the Big Capacitors
Install C6 and C7.
C6 and C7 are polarized. Be careful to get the polarity correct. Double check their
polarity before you solder them in place. They have large terminals, so it will take a fair
amount of heat and solder.
Designation Type Description Done? ()
C6 10,000 µF/80V Electrolytic capacitor
C7 2200 µF/160V Electrolytic capacitor
Caution: C6 and C7 are not identical! Be sure to put each in its correct place!

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Final Inspection of the Circuit Board
After you’ve taken a break, look over your completed circuit board one more time.
Looking on the component side, double check:
1. polarity (banded end) of diodes matching the banded end on the silk screen.
2. polarity of C1, C2, C6, C7 and C7 (minus sign away from the indicated plus sign
on the silk screen).
If you get one of these polarities wrong, there is a good chance that the power supply
won’t work, or there will be damage when you power it up.
Look at the solder side of the board. Make sure that:
1. All component leads are soldered (it’s easy to forget one or two, and that will
cause either unreliable operation, or no operation at all!)
2. There are no solder bridges between pads which should be isolated. Solder
bridges may stop the power supply from working correctly.
Power Supply Final Assembly
In this section, you’ll install Q5 while you mount the power supply circuit board silver
colored finned heatsink. The kit has two other heat sinks that are black in color. These
black anodized heat sinks are used for the amplifier modules.
Figure 6-Note the rounded brackets used for the power supply heatsink and PCB
1. Use two 6-32x3/8” screws to fasten a pair of mounting brackets to the heat sink,
placing the screw through the 9/64” clearance hole in the bracket. Note that one
hole in the mounting bracket is a 9/64” clearance hole, the other hole is threaded
to accept a 6/-32 screw. Don’t tighten the screws yet. Make sure you use the
brackets with the rounded edges to mount the power supply PCB.
2. Use two 6-32x1/4” screws to fasten the PCB to the mounting brackets and heat
sink, see Figure 10. Don’t tighten the screws yet.
3. Place a thin film of thermal compound on the metal tab surface of Q5 as shown in
Figure 7. Inset Q5 into the circuit board as shown in Figure 8. Secure it in place
with a #6-32x1/2” screw, just finger tight for now. The side with the thermal
compound must attach to the heat sink.
4. The previous step uses just a small amount of the thermal compound in the
squeeze tube. Put the squeeze tube in a safe place, as you may choose to use the
rest of its contents when you Fasten the Power Supply to the Chassis.

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Figure 7-Placing thermal compound on Q5
Figure 8-Installing Q5 on the heatsink and to the PCB
Figure 9-Remember to solder Q5's leads
5. Line up the PCB, brackets, and Q5 so everything is square and fits comfortably,
then tighten the 5 screws:
a. 2 that hold the brackets to the PCB

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b. 2 that hold the brackets to the heatsink
c. 1 that holds Q5 to the heatsink.
6. Solder the three leads of Q5 on the component side of the board, and clip the
leads. Inspect your work from both the top and the bottom of the board to make
sure there are no solder bridges between the leads.
Once the power supply/heat sink module is completed, set it aside and proceed to the next
section, where you will build the amplifier modules.
Figure 10-Assembled Power supply mounted on heat sink

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Figure 11-Component location guide for amplifier PCB's
Section 3: Assembling the Amplifier Circuit Boards
This section details the process of building the amplifier module circuit boards. We start
with an overview on this page. Begin by carefully emptying the contents of one of the
envelopes marked “GT-102 Amplifier Module” into a broad soup bowl, as shown in
Figure 12.
In general, you’ll start with the components that lay closest to the board, working your
way toward the taller components. You will:
1. Install the resistors
2. Install the small capacitors
3. Install the diodes
4. Install the LED
5. Install the medium size capacitors
6. Install the transistors
7. Install the big capacitor
8. Wind and install the output
inductor.
9. Install the relay.
10. Install the LM3886.
Figure 12-Empty the amplifier components into
a soup bowl

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Figure 13-Close-up of Amplifier board prior to U1, K1, and L1 installation
Install the Resistors
In general, you install the resistors by placing the body on the silk screen side of the
board, and the leads through the indicated holes. Bend the leads over on the back of the
board to keep the resistors from falling out until your solder them in place. Try to bend
the leads in a direction that won’t lead to solder bridges between traces that should
remain disconnected.
We recommend the following procedure:
1. Insert all the resistors of the same value, e.g. R14, R17, R3, and R5.
2. Bend the leads as described above.
3. Solder the leads on the back of the board.
4. Clip the leads.

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Figure 14-Four of the same value resistors are installed, leads bent on the back side, then soldered
and clipped.
To track your progress, place a check-mark in the done column as each resistor is
installed. Check resistor values with a meter and by reading the color code. Orient the
resistor with the fat brown band on the right, then you can read both the Color Code
column and the resistor from left to right.
Note: The GT-102 is a dual channel amplifier. You will build two identical channels.
We’ve provided two Done columns, Done1 for the first channel you build, and Done2 for
the second channel. We recommend that you build the channels one at a time, completing
the first channel, then returning to this point to build the second channel.
Designation Value Color Code Done
1
Done
2
R26 100 Brown, Black, Black, Black, Brown
R8 133K Brown, Orange, Orange, Orange, Brown
R3 100K Brown, Black, Black, Orange, Brown
R5 100K Brown, Black, Black, Orange, Brown
R14 100K Brown, Black, Black, Orange, Brown
R17 100K Brown, Black, Black, Orange, Brown
R1 10K0 Brown, Black, Black, Red, Brown
R7 10K0 Brown, Black, Black, Red, Brown
R28 10K0 Brown, Black, Black, Red, Brown
R29 10K0 Brown, Black, Black, Red, Brown
R30 10K0 Brown, Black, Black, Red, Brown
R4 1K Brown, Black, Black, Brown, Brown
R10 1K, 0.1% Brown, Black, Black, Brown, Violet;
In some kits, the resistor may have
numbers: 1K 0.1% on a brown body
R24 1M00 Brown, Black, Black, Yellow, Brown
R25 1M00 Brown, Black, Black, Yellow, Brown
R12 20K Red, Black, Black, Red, Brown
R11 20K,
0.1%
Red, Black, Black, Red, Violet
In some kits, the resistor may have
numbers: 20K 0.1% on a brown body.
R2 24K9 Red, Yellow, White, Red, Brown
R23 24K9 Red, Yellow, White, Red, Brown

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R27 40K2 Yellow, Black, Red, Red, Brown
R6 49K9 Yellow, White, White, Red, Brown
R9 49K9 Yellow, White, White, Red, Brown
The following resistors are 1 Watt resistors, having a larger body than the resistors
installed in the previous section.
R13 1000 (1 Watt) 5% Brown, Black, Red, Gold.
R20 2.2 (1 Watt) 5% Red, Red, Gold, Gold
R19 3300 (1 Watt) 5% Orange, Orange, Red, Gold
R15 10 (1 Watt) 5 % Brown, Black, Black, Gold.
R18 10 (1 Watt) 5% Brown, Black, Black, Gold
Install the Small Capacitors and the Diodes
Now we’ll install the following small capacitors:
Designation Value Marking Done
1
Done
2
C3 220 pF 221
C4 220 pF 221
C9 47 pF 470, or 47J
Here’s what these three caps look like (not to scale):
Next we install all the diodes except for the LED, which is installed a bit later.
Be careful! Diodes have a polarity. Make sure the band on the diode aligns with
the banded end of the silk screen!
Designation Value Marking, type Done1 Done2
D1 1N4004 4004, 1 amp 400 V diode
D4 1N4004 4004, 1 amp 400 V diode
D5 TZX6V2C 6V2, 6.2 V Zener diode
D2 BZX79-10 B10, 10 V Zener diode
D3 BZX79-10 B10, 10 V Zener diode
D8 BZX79-10 B10, 10 V Zener diode
D6 1N4148 4148, switching diode
Here’s what the 1N4004 diodes look like (not to scale):
And the rest of the diodes, with the exception of the LED look like this:
Next we install LED D7 (Light Emitting Diodes) – the green light from this LED will be
of medium brightness, and thus visible in a normally lit room.
Be careful! Light Emitting Diodes have a polarity, also! Read carefully to make

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sure you’re putting the diodes in the right way! The cathode of the LED is
indicated by a bar (negative sign) molded into the package. On some packages,
there is no bar, but seen from the top, the circular outline with have a flat side.
That flat side is the cathode. Finally, if the leads are uncut, the shorter of the two
leads will be the cathode.
Designation Value Package Done1 Done2
D7 LED T1 LED package
Figure 15-showing LED cathode orientation
Last Capacitors and the Transistors
Now install the medium tall polarized electrolytic capacitors:
C1, C6, C7, and C12 are polarized. Make sure the negative sign on the capacitors faces
away from the positive sign on the silk screen!
Designation Value Marking Done
1
Done
2
C1 100 µF, 50 V 100 µF, 50 V, and minus sign for polarity
C6 47 µF, 100 V 47 µF, 100 V, and minus sign for polarity
C7 22 µF, 50 V 22 µF, 50 V, and minus sign for polarity
C12 10 µF, 50 V 10 µF, 50 V, and minus sign for polarity