My Transcension 4 channel dimmer pack CDP405 stopped responding to DMX following a suspected power surge.
My first point of call was the power supply. It has a 1x240V to 2x15V transformer. Then a full wave rectifier into a 7805.
My voltages after the transformer 15VAC on each secondary, and the pulsating DC after the rectifier looks normal. However my 7805 was outputting 9V DC (measured using a BM786).
I replaced the 7805 now getting 4.9 V out but I have a pulse on the DC line. I probed it with the scope.
I have attached an image of the scope display.
What could be causing the pulsing? It doesn't look to me like the usual waveform I would expect for a dodgy capacitor. Perhaps indicating a short somewhere?
Any idea what to check next?