WORLD DESIGNS WDHD3S User manual

WDHD3S
Valve Headphone
Amplifier Kit
Assembly Instructions
www.world-designs.co.uk
07972 055492
HD3S Build 09/2013
WDHD3S
Valve Headphone
Amplifier Kit
Assembly Instructions
www.world-designs.co.uk
07972 055492
HD3S Build 09/2013

WDHD3S Kit Assembly Instructions
1
SAFETY WARNING
Lethal voltages exist in this amplifier. Even though this is a
straightforward kit in terms of construction, please do not attempt to
build it unless you have some understanding of valve circuitry and can
follow safety precautions.
We can’t guarantee an “office hours”back-up service, but please phone or
email if you run into any problems. Alternatively, visit our forum
www.world-designs.co.uk/forum where you will find first-class help and
advice.
Additionally, if the worst comes to the worst and you cannot get your
amplifier going, or simply want it checked, we will get your amplifier up
and running for a nominal charge.
For safety, never hold earthed metal work when testing. Make sure your
body is isolated by rubber soled shoes. To aid construction use a
multimeter, one capable of reading up to 500 volts DC. If you have
electrical safety gloves please wear them when testing, since the
greatest danger comes from a slip at this time. We recommend you use
insulated clip type multimeter probes to avoid having your hand inside
the amplifier when testing.
Always remove the AC POWER plug when you are soldering. The larger power
supply capacitors will hold a residual charge after switch off, so wear
your gloves at all times when working internally.
Additionally be aware that valves do get very hot and will burn skin on
contact, therefore please position in a safe place, away from children
and animals. Due to the heat dissipation from the circuit the case top
surface does get hot and the front panel may be warm to the touch.
FUSE
This amplifier consumes 350mA from the mains and must be fitted with a
500mA slow -blow fuse. If this blows then there is a fault which should be
cleared before the fuse is replaced. Do not be tempted to fit a higher
rated fuse since this could lead to damage to expensive components.
OUTPUT TRANSFORMERS
The output transformers must be connected to a load whenever the
amplifier is switched on -whether a dummy load (100 ohm resistors rated
at 2 watts or higher) or an old pair of headphones. This is because the
load is an integral part of the circuit (unlike most solid state
amplifiers). Running the amplifier without a load will cause unnecessary
distress to the output transformers and possible failure if left in this
state for a long time.
READING
Before you start building the amplifier read through the instructions at
least twice to familiarise yourself with the kit and its components and
avoid any mistakes.
WDHD3S Kit Assembly Instructions
1
SAFETY WARNING
Lethal voltages exist in this amplifier. Even though this is a
straightforward kit in terms of construction, please do not attempt to
build it unless you have some understanding of valve circuitry and can
follow safety precautions.
We can’t guarantee an “office hours”back-up service, but please phone or
email if you run into any problems. Alternatively, visit our forum
www.world-designs.co.uk/forum where you will find first-class help and
advice.
Additionally, if the worst comes to the worst and you cannot get your
amplifier going, or simply want it checked, we will get your amplifier up
and running for a nominal charge.
For safety, never hold earthed metal work when testing. Make sure your
body is isolated by rubber soled shoes. To aid construction use a
multimeter, one capable of reading up to 500 volts DC. If you have
electrical safety gloves please wear them when testing, since the
greatest danger comes from a slip at this time. We recommend you use
insulated clip type multimeter probes to avoid having your hand inside
the amplifier when testing.
Always remove the AC POWER plug when you are soldering. The larger power
supply capacitors will hold a residual charge after switch off, so wear
your gloves at all times when working internally.
Additionally be aware that valves do get very hot and will burn skin on
contact, therefore please position in a safe place, away from children
and animals. Due to the heat dissipation from the circuit the case top
surface does get hot and the front panel may be warm to the touch.
FUSE
This amplifier consumes 350mA from the mains and must be fitted with a
500mA slow -blow fuse. If this blows then there is a fault which should be
cleared before the fuse is replaced. Do not be tempted to fit a higher
rated fuse since this could lead to damage to expensive components.
OUTPUT TRANSFORMERS
The output transformers must be connected to a load whenever the
amplifier is switched on -whether a dummy load (100 ohm resistors rated
at 2 watts or higher) or an old pair of headphones. This is because the
load is an integral part of the circuit (unlike most solid state
amplifiers). Running the amplifier without a load will cause unnecessary
distress to the output transformers and possible failure if left in this
state for a long time.
READING
Before you start building the amplifier read through the instructions at
least twice to familiarise yourself with the kit and its components and
avoid any mistakes.

WDHD3S Kit Assembly Instructions
2
SKILL LEVEL
To build this unit you must be able to:
a) solder to a good standard
b) have some knowledge of valve circuitry
c) possess a rudimentary understanding of electricity and electronics
d) have a multimeter and be able to use it
e) know the precautions necessary to avoid electric shocks from the
AC mains and amplifier power lines
f) have access to a dummy load or an old pair of headphones
g) identify components, particularly resistors, using either the markings
or a multimeter.
A NOTE ON TINNING
For ease of use we make every effort to provide tinned copper wire with
this kit, however there are occasionally supply problems and we are
unable to do so. We recommend that you “tin”any bare copper wire before
making a joint.
A NOTE ON HEAT-SHRINK
If you have not used heat -shrink before, the only difficult thing is to
remember to slide an appropriate length of heat -shrink over the wires
BEFORE soldering the joint! Slide the sleeving completely over the bare
wires and carefully apply heat from a mini heat -gun (available cheaply
over the internet) or from a cigarette lighter, taking care not to damage
any PVC insulation nearby. We supply plenty of heat -shrink, so do
practice a couple of times before you set out.
BUILD SEQUENCE
Before you start building it is a good idea to check the parts supplied
against your parts list. Please be aware that “picking errors”do happen
even if very infrequently -make sure that you check the value and rating
of each component carefully. A schematic of resistor colour coding is
given at the end of this booklet. Use the check column on the parts list
to cross off your components. To help you through the build process you
will find throughout the manual diagrams and photographs labelled Fig. 1,
Fig. 2 and so on. These will bear correlation to the text and to the
highlighted figure in the margins.
WDHD3S Kit Assembly Instructions
2
SKILL LEVEL
To build this unit you must be able to:
a) solder to a good standard
b) have some knowledge of valve circuitry
c) possess a rudimentary understanding of electricity and electronics
d) have a multimeter and be able to use it
e) know the precautions necessary to avoid electric shocks from the
AC mains and amplifier power lines
f) have access to a dummy load or an old pair of headphones
g) identify components, particularly resistors, using either the markings
or a multimeter.
A NOTE ON TINNING
For ease of use we make every effort to provide tinned copper wire with
this kit, however there are occasionally supply problems and we are
unable to do so. We recommend that you “tin”any bare copper wire before
making a joint.
A NOTE ON HEAT-SHRINK
If you have not used heat -shrink before, the only difficult thing is to
remember to slide an appropriate length of heat -shrink over the wires
BEFORE soldering the joint! Slide the sleeving completely over the bare
wires and carefully apply heat from a mini heat -gun (available cheaply
over the internet) or from a cigarette lighter, taking care not to damage
any PVC insulation nearby. We supply plenty of heat -shrink, so do
practice a couple of times before you set out.
BUILD SEQUENCE
Before you start building it is a good idea to check the parts supplied
against your parts list. Please be aware that “picking errors”do happen
even if very infrequently -make sure that you check the value and rating
of each component carefully. A schematic of resistor colour coding is
given at the end of this booklet. Use the check column on the parts list
to cross off your components. To help you through the build process you
will find throughout the manual diagrams and photographs labelled Fig. 1,
Fig. 2 and so on. These will bear correlation to the text and to the
highlighted figure in the margins.

WDHD3S Kit Assembly Instructions
Fit the earth terminal to the rear of the case. If necessary
remove some of the paint around the earth terminal hole so that
the terminal makes electrical contact with the case. Remove the
earth terminal binding nut and fit the terminal using a serrated
washer on the inside of the panel. Tighten the nut fully.
Fit phono sockets to the rear panel -red towards the bottom of
the amplifier, and black towards the top. Fit the solder tags so
that each pair of tags point towards each other and bend them
away from the chassis. When you have tightened the nuts fully
check with a continuity meter that the phono plugs are
electrically isolated from the chassis.
Fit the potentiometer to the front panel using the washer and
nut provided. Scrape some paint away from inside the chassis to
make sure that the body of the potentiometer is grounded.
Fit the headphone socket to the front panel using the washer and
nut provided. Offer up the front panel to the chassis to make
sure that the socket sits centrally in the hole in the fascia,
and adjust if necessary. Note that the PCB star earth will be
connected to the chassis via the headphone socket -it is
important to scrape some paint away from the inside of the
chassis where it meets the socket. Tighten the nut fully and
check for electrical continuity between the body of the socket
and the earth post.
Fit the power transformer using the mounting kit supplied.
Insert the bolt from the underside of the case, then fit a pad
to the inside of the case followed by the toroid, another pad
and, finally, the top plate and nut. Align the toroid so that
the secondary leads (Orange / Orange / Yellow and Red / Black) lie
closest to the PCB position. Tighten the nut to clamp the toroid
firmly in position.
3
Fig. 2
FITTING THE HARDWARE
full nut
metal washer
rubber washer
rubber washer
chassis base surface
bolt
toroidal
mains
transformer
Fig. 1 Toroid Mounting Kit
Figs.
1/2
Fig. 3
WDHD3S Kit Assembly Instructions
Fit the earth terminal to the rear of the case. If necessary
remove some of the paint around the earth terminal hole so that
the terminal makes electrical contact with the case. Remove the
earth terminal binding nut and fit the terminal using a serrated
washer on the inside of the panel. Tighten the nut fully.
Fit phono sockets to the rear panel -red towards the bottom of
the amplifier, and black towards the top. Fit the solder tags so
that each pair of tags point towards each other and bend them
away from the chassis. When you have tightened the nuts fully
check with a continuity meter that the phono plugs are
electrically isolated from the chassis.
Fit the potentiometer to the front panel using the washer and
nut provided. Scrape some paint away from inside the chassis to
make sure that the body of the potentiometer is grounded.
Fit the headphone socket to the front panel using the washer and
nut provided. Offer up the front panel to the chassis to make
sure that the socket sits centrally in the hole in the fascia,
and adjust if necessary. Note that the PCB star earth will be
connected to the chassis via the headphone socket -it is
important to scrape some paint away from the inside of the
chassis where it meets the socket. Tighten the nut fully and
check for electrical continuity between the body of the socket
and the earth post.
Fit the power transformer using the mounting kit supplied.
Insert the bolt from the underside of the case, then fit a pad
to the inside of the case followed by the toroid, another pad
and, finally, the top plate and nut. Align the toroid so that
the secondary leads (Orange / Orange / Yellow and Red / Black) lie
closest to the PCB position. Tighten the nut to clamp the toroid
firmly in position.
3
Fig. 2
FITTING THE HARDWARE
full nut
metal washer
rubber washer
rubber washer
chassis base surface
bolt
toroidal
mains
transformer
Fig. 1 Toroid Mounting Kit
Figs.
1/2
Fig. 3

Fig. 3 Hardware Fittings (front panel)
Fig. 2 Hardware Fittings (rear panel)
WDHD3S Kit Assembly Instructions
4
Fit the output transformers to the chassis, using M4x10 screws, serrated
washers and nuts, positioning the secondary leads (blue x 4 and purple x
4) towards the outside of the chassis.
Fit the stand-offs for the PCB using M3x12 screws from the underside of
the chassis.
Fig. 3 Hardware Fittings (front panel)
Fig. 2 Hardware Fittings (rear panel)
WDHD3S Kit Assembly Instructions
4
Fit the output transformers to the chassis, using M4x10 screws, serrated
washers and nuts, positioning the secondary leads (blue x 4 and purple x
4) towards the outside of the chassis.
Fit the stand-offs for the PCB using M3x12 screws from the underside of
the chassis.

Fig. 4 IEC Input Links
WDHD3S Kit Assembly Instructions
5
WIRING THE MAINS SUPPLY
mains transformer 2e
blue wire
mains transformer 2e
brown wire
BLADE 1
BLADE 2
BLADE 3
BLADE 4
BLADE 5
BLADE 6
BLADE 7
to Chassis Ground
Fig. 4 Using a short length of 1mm brown wire link Blades 1 and 5 of
the IEC input. Using a short length of 1mm blue wire link Blades
4 and 6 of the IEC input. These joints should be insulated with
heat -shrink sleeving. Take approx 75mm Green / Yellow wire and
solder one end to Blade 7 of the IEC input and the other to a
solder tag.
Fig. 4 IEC Input Links
WDHD3S Kit Assembly Instructions
5
WIRING THE MAINS SUPPLY
mains transformer 2e
blue wire
mains transformer 2e
brown wire
BLADE 1
BLADE 2
BLADE 3
BLADE 4
BLADE 5
BLADE 6
BLADE 7
to Chassis Ground
Fig. 4 Using a short length of 1mm brown wire link Blades 1 and 5 of
the IEC input. Using a short length of 1mm blue wire link Blades
4 and 6 of the IEC input. These joints should be insulated with
heat -shrink sleeving. Take approx 75mm Green / Yellow wire and
solder one end to Blade 7 of the IEC input and the other to a
solder tag.

Fig. 5 IEC Input Wiring
WDHD3S Kit Assembly Instructions
6
Select the AC voltage for the power transformer to suit your AC
mains supply voltage as follows:
220 -240V : Solder the grey and purple primary wires together
and insulate the joint. Twist these wires together and coil them
neatly out of the way. Twist the blue and brown wires together,
pass them through the piercing in the chassis, and solder blue
to pin 3 and brown to pin 2 of the IEC input. These joints
should be insulated with heat-shrink sleeving.
100 -120V : Twist all the primary wires together, pass them
through the piercing in the chassis, and solder the blue and
purple wires to pin 3 and the brown and grey wires to pin 2 of
the IEC input. These joints should be insulated with heat-shrink
sleeving.
Making sure that the power switch is positioned nearest the
outside of the chassis, fit the IEC input into the hole in the
chassis and snap it into place. The lugs should provide a secure
fix. Connect the Green / Yellow wire from Blade 7 to the chassis
Earth Post.
NB: The fuse is held in a pull -out tray in the IEC input -you
may wish to fit it now. Please note the precautions on fuse
rating in the Safety Warning at the beginning of the manual.
Fig. 5
Fig. 5 IEC Input Wiring
WDHD3S Kit Assembly Instructions
6
Select the AC voltage for the power transformer to suit your AC
mains supply voltage as follows:
220 -240V : Solder the grey and purple primary wires together
and insulate the joint. Twist these wires together and coil them
neatly out of the way. Twist the blue and brown wires together,
pass them through the piercing in the chassis, and solder blue
to pin 3 and brown to pin 2 of the IEC input. These joints
should be insulated with heat-shrink sleeving.
100 -120V : Twist all the primary wires together, pass them
through the piercing in the chassis, and solder the blue and
purple wires to pin 3 and the brown and grey wires to pin 2 of
the IEC input. These joints should be insulated with heat-shrink
sleeving.
Making sure that the power switch is positioned nearest the
outside of the chassis, fit the IEC input into the hole in the
chassis and snap it into place. The lugs should provide a secure
fix. Connect the Green / Yellow wire from Blade 7 to the chassis
Earth Post.
NB: The fuse is held in a pull -out tray in the IEC input -you
may wish to fit it now. Please note the precautions on fuse
rating in the Safety Warning at the beginning of the manual.
Fig. 5

WDHD3S Kit Assembly Instructions
7
POPULATING THE PCB
The PCB is double -sided. In this manual the side with the
component “legends”(indicating where the components should be
sited) printed on it is referenced as the component side and the
other side as the solder side.
Where possible it is advisable to solder the legs of the
components to both sides of the PCB. The holes in the PCB are
“plated -through”meaning that soldering both sides is not
strictly necessary. It is nonetheless good practice to ensure a
good joint and to provide mechanical security -the board is
subject to repeated heating and cooling which can produce stress
and cracked joints.
If you ever need to “drill out”any holes in order to fit
upgraded components it is ESSENTIAL to solder both sides of the
joint.
When fitting PCB Pins they should be pressed into place with a
hot soldering iron (make sure the pins get hot before pushing
them fully home) and then soldered on each side of the board.
Where possible it is good practice to fit components with the
lowest profile (eg links or low value resistors) first and those
with the highest profile (eg large capacitors) last.
FIT THE VALVE BASES.
The valve bases should be fitted to the component side of the
PCB. Make sure that you solder the legs on both sides of the PCB
to give a secure mechanical (as well as electrical) joint.
FIT THE PCB PINS.
We have highlighted the PCB pin positions in colour on the
photograph overleaf so that you can find them easily (the
picture also shows the soldering points for the heater links,
highlighted in white). Solder the pins so that they project on
the component side of the board in the following positions:
POWER SUPPLY: HTR CT Y, HTR-OR, HTR+OR, BLACK, RED (5 pins,
highlighted in light blue in Fig. 7)
OUTPUT TRANSFORMER PRIMARIES / TERTIARIES: OPTXL BLACK, RED HT L,
FBL, FBLG, OPTXR BLACK, HT R RED, FBR, FBRG (8 pins, highlighted
in red in Fig. 7)
OUTPUT TRANSFORMER SECONDARIES: B3, P1, B4, P2, B2, P3, B1, P4
for both channels (16 pins, highlighted in yellow in Fig. 7)
INPUTS: IPL, IPLG, IPR, IPRG (4 pins, highlighted in dark blue
in Fig. 7)
OUTPUTS: OPL, OPLG, OPR, OPRG (4 pins, highlighted in green in
Fig. 7)
LED: LED-, LED+(2 pins, highlighted in orange in Fig. 7)
Fig. 10
Figs.
7/10
WDHD3S Kit Assembly Instructions
7
POPULATING THE PCB
The PCB is double -sided. In this manual the side with the
component “legends”(indicating where the components should be
sited) printed on it is referenced as the component side and the
other side as the solder side.
Where possible it is advisable to solder the legs of the
components to both sides of the PCB. The holes in the PCB are
“plated -through”meaning that soldering both sides is not
strictly necessary. It is nonetheless good practice to ensure a
good joint and to provide mechanical security -the board is
subject to repeated heating and cooling which can produce stress
and cracked joints.
If you ever need to “drill out”any holes in order to fit
upgraded components it is ESSENTIAL to solder both sides of the
joint.
When fitting PCB Pins they should be pressed into place with a
hot soldering iron (make sure the pins get hot before pushing
them fully home) and then soldered on each side of the board.
Where possible it is good practice to fit components with the
lowest profile (eg links or low value resistors) first and those
with the highest profile (eg large capacitors) last.
FIT THE VALVE BASES.
The valve bases should be fitted to the component side of the
PCB. Make sure that you solder the legs on both sides of the PCB
to give a secure mechanical (as well as electrical) joint.
FIT THE PCB PINS.
We have highlighted the PCB pin positions in colour on the
photograph overleaf so that you can find them easily (the
picture also shows the soldering points for the heater links,
highlighted in white). Solder the pins so that they project on
the component side of the board in the following positions:
POWER SUPPLY: HTR CT Y, HTR-OR, HTR+OR, BLACK, RED (5 pins,
highlighted in light blue in Fig. 7)
OUTPUT TRANSFORMER PRIMARIES / TERTIARIES: OPTXL BLACK, RED HT L,
FBL, FBLG, OPTXR BLACK, HT R RED, FBR, FBRG (8 pins, highlighted
in red in Fig. 7)
OUTPUT TRANSFORMER SECONDARIES: B3, P1, B4, P2, B2, P3, B1, P4
for both channels (16 pins, highlighted in yellow in Fig. 7)
INPUTS: IPL, IPLG, IPR, IPRG (4 pins, highlighted in dark blue
in Fig. 7)
OUTPUTS: OPL, OPLG, OPR, OPRG (4 pins, highlighted in green in
Fig. 7)
LED: LED-, LED+(2 pins, highlighted in orange in Fig. 7)
Fig. 10
Figs.
7/10

Fig. 8 Diode Polarity
Fig. 7 PCB Pin and Heater Link Positions
8
WDHD3S Kit Assembly Instructions
FIT THE DIODES.
Fit the diodes D1, D2, D3 & D4. Orientation is very important -
note that the stripe on the diode matches with the stripe on the
PCB legend for correct polarity.
FIT THE RESISTORS.
Elevate the higher power resistors R1, R2, R4, R6, R11, R13,
R17, R18, R19 from the PCB by at least 10mm as they require a
cooling flow of air around them.
Figs.
8/10
Fig. 10
Fig. 8 Diode Polarity
Fig. 7 PCB Pin and Heater Link Positions
8
WDHD3S Kit Assembly Instructions
FIT THE DIODES.
Fit the diodes D1, D2, D3 & D4. Orientation is very important -
note that the stripe on the diode matches with the stripe on the
PCB legend for correct polarity.
FIT THE RESISTORS.
Elevate the higher power resistors R1, R2, R4, R6, R11, R13,
R17, R18, R19 from the PCB by at least 10mm as they require a
cooling flow of air around them.
Figs.
8/10
Fig. 10

WDHD3S Kit Assembly Instructions
9
Figs.
7/11
FIT THE DIL SWITCHES.
Orientation is important -note the “on ”printed on the PCB and
on the switches (the individual switches “1”and “12”are also
printed as legends on the PCB). Be very careful when soldering
not to accidentally link across solder points with excess
solder.
FIT ALL THE CAPACITORS.
Note that the electrolytic capacitors C1, C2, C3, C4, C5, C7, C8
are polarized, and ensure they are fitted correctly. The PCB is
printed with a +sign where polarity needs to be observed. The
capacitors are normally printed with a white (occasionally black
or gold) bar which denotes the negative terminal as shown below.
FIT THE HEATER LINKS.
We have highlighted the solder points for the heater links in
white on the photograph at Fig. 7 so that you can find them
easily. Note that the links should be fitted to the solder side
of the PCB and care should be taken to ensure that the sharp
ends of the components, where they are soldered through the PCB,
do not damage the insulation of the wires. Taking twisted pairs
of brown and grey wire, use the brown wires to connect point
HTR+(next to pin HTR+OR) to HTR+at V2 and onwards to HTR+at
V1. Similarly, using the grey wires, connect HTR-(next to pin
HTR-OR) to HTR-at V2 and onwards to HTR-at V1.
(“HTR+”and “HTR-”are, in fact misprints on the PCB -the
heaters operate on AC) -but the markings make it easier to wire
the heaters of both valves the same way round.)
FIT THE LED.
Solder approx 75-100mm red wire to the long leg of the LED and a
similar length of black wire to the short leg. Insulate the
joints and the bare legs of the LED with heat-shrink sleeving.
Twist the wires together to provide mechanical stability and
solder the red wire to the LED+pin and the black to the LED-
pin on the PCB. The LED can be passed through the hole in the
chassis ready for fixing to the fascia when you come to do this.
Because access is restricted later, solder approx 100mm red wire
to each of the pins OPL and OPR, and a similar length of black
wire to pins OPLG and OPRG.
(-) negative terminal
(+) positive terminal (-) negative terminal
(+) positive terminal
Fig. 9 Capacitor Polarity Markings for C4, C5, C7, C8 (left)
and C1, C2, C3 (right)
Fig.10
Figs.
9/10
WDHD3S Kit Assembly Instructions
9
Figs.
7/11
FIT THE DIL SWITCHES.
Orientation is important -note the “on ”printed on the PCB and
on the switches (the individual switches “1”and “12”are also
printed as legends on the PCB). Be very careful when soldering
not to accidentally link across solder points with excess
solder.
FIT ALL THE CAPACITORS.
Note that the electrolytic capacitors C1, C2, C3, C4, C5, C7, C8
are polarized, and ensure they are fitted correctly. The PCB is
printed with a +sign where polarity needs to be observed. The
capacitors are normally printed with a white (occasionally black
or gold) bar which denotes the negative terminal as shown below.
FIT THE HEATER LINKS.
We have highlighted the solder points for the heater links in
white on the photograph at Fig. 7 so that you can find them
easily. Note that the links should be fitted to the solder side
of the PCB and care should be taken to ensure that the sharp
ends of the components, where they are soldered through the PCB,
do not damage the insulation of the wires. Taking twisted pairs
of brown and grey wire, use the brown wires to connect point
HTR+(next to pin HTR+OR) to HTR+at V2 and onwards to HTR+at
V1. Similarly, using the grey wires, connect HTR-(next to pin
HTR-OR) to HTR-at V2 and onwards to HTR-at V1.
(“HTR+”and “HTR-”are, in fact misprints on the PCB -the
heaters operate on AC) -but the markings make it easier to wire
the heaters of both valves the same way round.)
FIT THE LED.
Solder approx 75-100mm red wire to the long leg of the LED and a
similar length of black wire to the short leg. Insulate the
joints and the bare legs of the LED with heat-shrink sleeving.
Twist the wires together to provide mechanical stability and
solder the red wire to the LED+pin and the black to the LED-
pin on the PCB. The LED can be passed through the hole in the
chassis ready for fixing to the fascia when you come to do this.
Because access is restricted later, solder approx 100mm red wire
to each of the pins OPL and OPR, and a similar length of black
wire to pins OPLG and OPRG.
(-) negative terminal
(+) positive terminal (-) negative terminal
(+) positive terminal
Fig. 9 Capacitor Polarity Markings for C4, C5, C7, C8 (left)
and C1, C2, C3 (right)
Fig.10
Figs.
9/10

Fig. 11 Heater Links
Fig. 10 Populated Printed Circuit Board
10
WDHD3S Kit Assembly Instructions
Fig. 11 Heater Links
Fig. 10 Populated Printed Circuit Board
10
WDHD3S Kit Assembly Instructions