Toshiba S-AV17 /50W power circuit used in some mobile stations for 2m band (for example DRAGON SY130) suddenly lost power after using the station for a while. This is a typical defect of these amplifiers, which consists in the cracking of the ceramic plate on which the entire circuit board is applied, and the subsequent interruption of the circuit board in two places, see the red lines in figure 1 and in fig. 2.
Due to the fact that the ceramic is stuck on a 3 mm thick copper plate, it is not possible to connect it using soldering due to the immediate heat dissipation on the plate. Since the price of a new power circuit often exceeds the value of the device itself in which it is used, I decided to repair the circuit. Just heat the stove plate to temperature (before the tin starts to melt) and place the circuit on the plate. It is even better to use an older discarded iron with a thermostat, which you fix by the handle into the clamp. During half a minute, a micro soldering iron can be gradually flown into the cracked printed circuit and with the help of a watchmaker's magnifying glass and tweezers, one copper wire can be shaped, for example from a mains cable, see the yellow line in fig. 3. After cooling down and re-mounting the device, the circuit works reliably again.
WARNING!! Do not dig or mechanically disturb the silicone on the power elements. They contain highly poisonous substances.
Source: http://pd0rkc.ontwikkel.nl
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