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<blockquote data-quote="vlammie" data-source="post: 474076" data-attributes="member: 270173">Check D5/R9 which provide the main Vcc voltage after turn-on. If this is missing, it could be causing the tripping. Be careful when checking this side of the supply though!Llew</blockquote>Hi LlewI will take care. I have been &quot;shocked&quot; in the past when I was young:-HoHo and also have blown up some probes already :-googlyI work now with an oscilloscoop &quot;of ground&quot; which is dangerous also. So don't experiment with this if you don't know what you are doing. Thanks for your tips. I had tried these all already, but did not find any defect components in the power supply of IC1. I measure a steady voltage of 17.1 Vdc at pin 3 of IC1 after starting up. What I also see is that the SMPS has already problems starting up unloaded. It makes already a number of hicks (about 10) before it is stable. Hicks have an interval of around 100 ms.[/QUOTE]

[QUOTE="vlammie, post: 474076, member: 270173"] Check D5/R9 which provide the main Vcc voltage after turn-on. If this is missing, it could be causing the tripping. Be careful when checking this side of the supply though! Llew[/QUOTE] Hi Llew I will take care. I have been "shocked" in the past when I was young:-HoHo and also have blown up some probes already :-googly I work now with an oscilloscoop "of ground" which is dangerous also. So don't experiment with this if you don't know what you are doing. Thanks for your tips. I had tried these all already, but did not find any defect components in the power supply of IC1. I measure a steady voltage of 17.1 Vdc at pin 3 of IC1 after starting up. What I also see is that the SMPS has already problems starting up unloaded. It makes already a number of hicks (about 10) before it is stable. Hicks have an interval of around 100 ms. [/QUOTE]

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