10W HF Linear PA kit assembly
1.00
31
5) Insert the two white plastic insulating washers into the holes in the IRF510, and pass
through the two 9mm bolts.
6) On the bottom of each IRF510 tab, put one of the remaining two blue insulating TO220
pads. It is very important to make sure that the pad completely covers the IRF510 tab. It
has to insulate the tab because the tab must not touch the heatsink which is grounded.
7) The final 9mm M3 bolt is used to bolt the 7805 voltage regulator to the heatsink.
8) Now mount the heatsink. If all is well, the four M3 bolts (one through the 7805 regulator, two
through the two IRF510s, and one through the BS170 driver heatsink assembly) should all
line up perfectly with their respective holes in the heatsink. This heatsink is custom-
designed to fit the QSX PCB assembly perfectly.
9) Now tighten all the bolts. Make them tight, but not so tight that you risk breaking threads
and/or never being able to undo them ever again.
10) Finally it is very important to check now, that there is no short-circuit between the tabs of
the IRF510 and the heatsink. To do this, you can put the DVM probes between GND and
the +12V bus. A convenient place to do this, is at the connections of the PA PCB to the
main rear PCB. The leftmost two wires are +12V and GND respectively. You can touch the
probes to these connection points, with the board assembly upside-down.
11) When powering up the radio, it is best to use a current-limited supply, set to 300mA, as a
final precaution.
