. . .
Solution 3: 78L09. the center lead looks soldered but it is floating but
the tab is soldered to the copper
below it. The white wire is my fix for prevent the filter relays from
clicking during PTT. Yes the board
needs a brush cleaning!
The audio is fine but distorts at high volume. The 9V voltage out does
not drop at max volume.
At 06-03-18, you wrote:
I did some experiments with the
FCI chips were sourced locally and plugged in. No failure with normal
I raised the volume to a high level and the chip failed
1: Add a resistor in series with the 12V line maybe 10-15 ohms to drop
2. Simple solution is to use only a 16 Ohm speaker or add a series
8-10 Ohm resistor with the 8 ohm speakers.
3. Cut the power track to the TDA and insert a 78L08 or 9 to reduce the
voltage. There is a track which can be cut
and a SMD or leaded regulator can be soldered on the
board. This track leads directly to the chip and filter cap.
The second solution may be the simplest.
Further experimentation scheduled for tomorrow!