4.2.4
Transistor in plastic case and metal clip(s)
shunt for current
measurement
Before changing the transistors verify the shunt of the
current measurement.
The value (imprinted) should be between 0,5 and 10
Ω
.
If this resistor has blown, further damages are probable
and the equipment must be returned to the supplier for
repair.
The exchange is to be made as follows:
-
Unscrew the head screws M3 and remove the fixing clip(s). (Caution: when removing the screw the
cooling plate is unfixed as well. It only sticks by the thermal compound.)
-
Cut the transistor legs underneath the transistor with a side cutter.
-
Remove the transistor with the insulating tube.
-
Unsolder transistor connections.
Attention: No strength must be applied when pulling out the transistor legs. Prefere desoldering
using a vacuum-pump instead of pulling the pin. If there are too much remnants of
soldering tin or flux, than they have to be removed separately. If necessary disassemble
the generator (not unplugging the wired connections). Remove the four screws from the
board. Turn the board upside-down lifting the side with the transformer, HF-terminals
and transistors over the opposite side (containing the mains fuse and the current shunt).
Care for the cooling plate, which must not be moved.
Note for the assembly: The 4 short screws are intended to fixate the plate, the longer
screw is for the fixing clip.
Tighten the screws by hand!
-
Examine, whether the cooling plate was shifted, possibly adjust (it must not overlap with the board)
and assemble the transistors with the fixing clip. Therefore, plug in transistors into holes. The
transistor legs should look trough the hole by about 1 mm. Do not cut the legs, but adjust them.
Bend the transistors until they fit on the cooling plate (slight spring back is allowed). Next step is
soldering the transistor connections.
-
Slide the standard insulating tube over the new transistor until it stuck on the board, but not between
board and transistor connections.
Attention: Handle cautiously – already small rifts or holes at the bottom side of the tube will cause
malfunction.
-
No recalibration of power or frequency is required.
insulating tube
fixing clip
transistor in
insulating tube
generator bard
cooling plate
base plate (housing)
cross recessed pan head screw M3
generator board
8
