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FM900 - 91 -92 Auto power up mod

The power up board can be mounted on to the synthesizer board. The output of the board is connected to the top of R246. The un-switched 13.8v to R409 and the switched 13.8v to R410.

Operation
This circuit is aggressive, if there is about 13.8 on the unswitched the 555 will oscillate until 13.8 is on the switched, this will inhibit the 555, until power is removed from the switched. If one presses the front on/off. The radio will switch off then switch back on again so an external power switch is required for servicing the fuse holder can serve as this.

Download Express pcb file

This was jammed in for testing only.