Hi Vegoil, sorry I didn`t get involved in this conversation earlier. There are several reasons why an SOM does not auto start. None of them involve the large rectifier and associated capacitor.
For these to start 12 volts has to flow through the detection circuit and closes the small relay, this triggers the start up sequence, the switch must be on Auto and there must be a load. Once the generator is up to speed and making 240 volt AC, the large rectifier and capacitor turn some of this 240 volts AC into 350 volt DC. This DC voltage is used to close the large relay switching 240 volt AC to the load and switching over the 12 volt DC detection circuit to a rectified 12 volts generated across the wire wound toroidal core.
Once the load current stops flowing the rectified 12 volt also stops, opening the small relay and triggering the shut down sequence.
If you manually close the small relay (don`t use your fingers!) does this trigger the start sequence? With a load applied does the generator sustain generation if you manually close the small relay? (Switch in Auto position)
There should be two old rectifiers in the control panel, strongly recommend you replace these with modern diodes, the smoothing capacitor on mine is only 4 micro-farad so 25 would be fine, it must be rated at no less than 400 volt. When working with large capacitors like this always short across the terminals before handling, 400 volts DC will give you a nasty shock!
Please also clean and adjust Line contactor 2 on the large relay.
Bob