A and T Labs
K6 Audio Power Amplifier Assembly Manual
2001 A and T Labs Inc.
AMK6a
13
3.4 POWER SUPPLY FLANGE MOUNTED COMPONENTS
Power supply heat sink mounted components may be mounted at this time. The power
transistors and rectifiers mount at the edge of the board, so you will need to align these
with your heat sink drilling before soldering to ensure proper alignment. Mount all
power components with insulators coated with a liberal layer of heat sink conductive
white silicone grease. Tighten well, but do not over tighten – ensure insulators do not
deform under pressure. Using an ohm meter, ensure that there are no shorts between
transistor cases and the heat sink. Solder the components to the board. This should
complete the power supply assembly, including the angle flange.
3.4.1 Power Supply Power Components
ü
Part
Description
ü
Part
Description
ü
Part
Description
D1
FR805
D4
FR805
Q3
IRFP450
D2
FR805
Q1
IRFP450
Q4
IRFP450
D3
FR805
Q2
IRFP450
REG2 7812
4. TESTING
4.1 INVERTER TESTING (Without oscilloscope)
Begin by once again looking over the inverter board for completeness and correctness
of parts values and orientation. Also re-check the quality of all solder connections.
Next, install F1 and F2, but leave out F3. Make sure jumpers Jmp1, 2, 3, and 4 are
installed properly for the supply voltage of intended use (see section 3.2). Apply input
power from a power cord, temporarily connected to the AC input terminals, labeled “N”
and “LIVE”. From here on, remember to exercise extreme caution in handling and
measuring, since the input portions of the inverter are directly connected to the power
line. Also note the rectified line filter capacitors will store a substantial charge for some
time after the unit is turned off and pose a serious electrocution or damage threat. It is
a good idea to discharge them with a low value resistor before handling the supply.
Measure at the input to F3 with respect to the ground side of C2 and verify the
presence of 320 volts. Also, measure the output of REG1 with respect to board ground,
and check for +12 volts (+/- .5v). Double check the orientation of T2. Turn off input
power and install F3.
For the next test it is advisable to load the output of the inverter lightly, say with a 5K,
10 Watt resistor per rail. Set switch SW2 to the 41 volt position, and apply power.
Check for +/- 41 (+/- 2) volts at the inverter output. Switch SW2 to +/- 58 volts and +/-
82 volts (+/- 2), and check for each voltage at the output.
