CEN
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Advertisers Index
Our advertisers are vital to the
success of SILICON CHIP. Please
give them your support.
Altronics ............. ..
36,37,44,
45,60 ,61
Arista Electronics .... .. .. .. .. ... 4 7
2
3
4
5
6
7
8
9
10
11
12
13
14
15 ($7.00)
Name
Postcode
Enclosed is my cheque or money order for$ ....... ...... ..... ..... .... ..... . .. or please debit my
Bankcard □
Visa □
Marantz Australia . . ..... . .. . ... IFC
Microbee .. ....... ....... .. ...... IBC
RCS Radio .. ........... ........ .. 49
Card No .. ...
Scan Audio Pty Ltd .......... ..
Signature ..
Tandy Electronics ....... .. .. OBC
High-power amplifier module transistors and the driver transistors. Mount the power transistors first.
These must all be isolated from
the heatsink by using mica washers
and insulating bushes, as depicted
in Fig.5. Smear all mounting surfaces with heatsink compound
before assembly. Solder the mounting nuts to the PCB pattern after
assembly to ensure reliable contact. Alternatively, if the nuts are
nickel plated or stainless steel, use
lockwashers.
The two driver transistors and
the Vbe multiplier (Q7) are bent
over and also attached to the heatsink bracket using T0-126 mounting
kits. (See Fig.6).
When the whole assembly is completed, the heatsink bracket should
be attached to a suitably large heatsink, preferably with vertical fins.
Heatsink compound should be used
between the bracket and the heatsink to improve heat transfer.
Before applying power remove
the two fuses from the board clips
and set VR1 fully anticlockwise.
96
Dick Smith Electronics .....
Jemal Products ................. 59
Address ..... .. ... .......... ......... .... .... .. ......... .. ....... ... ........ ... ........ . .
Suburb/Town ....... ....... .... ... .......... ........ .. ..... ......... ... ..... .....
67
8,9 ,
16,48,54,55
Emona . .. .. ... ........ .. .. .... .... . 43
Jaycar Electronics .. ... .. . 20-27
Crusader ..... ...... .. .. ........ .. .
SILICON CHIP
89
ctd from page 15
This gives the setting for minimum
quiescent current through the output transistors. Solder a 5600 5W
wirewound resistor across each
fuseholder. Set your multimeter to
the 200VDC range (or no lower than
50V DC if an analog meter).
Now apply power and measure
the positive and negative supply
rails. They should be within a few
volts of ± 40V. Now measure the
other voltages on the circuit. They
should all be within ± 10% of the
nominal values. The voltage at the
output should be within ± 30mV of
OV. No load should be connected at
this stage, by the way.
Now switch your multimeter
back to the 200V DC range and connect it across one of the 5600
resistors. Adjust VR1 for a reading
of 28 volts. This gives a total quiescent current of 50 milliamps.
For the 50W version which uses
only two output transistors, VR1
should be adjusted for a reading of
14 volts. This gives a total quies cent
current of 25 milliamps.
After five minutes or so, check
{-·~"
WASHER
-T0126
i(F~
r~ ___
11
O
O:~::E
WASHER
- - HEATSINK
PCB
..l_
...- SHAKE·PR00F
WASHER
f;f!!J-NUT
Fig.6: mounting details for the T0-126
transistors. Note that heatsink
compound should be lightly smeared
on the mounting surfaces.
the quiescent current and readjust
VR1 if necessary to get the correct
voltage across the 5600 resistor.
Now switch off, remove the two
5600 resistors and insert the fuses.
The module is now ready for use.
