[hvalentim]

I'm using one of those cheap chinese solar regulators, for more than two years, and my TX unit with a 7809 is happily working with it.

I do not doubt either your judgment of experience. I am sure they might do a reasonable job under moderate use.

I am just saying I have seen similar models fry easily and I would not trust them for more demanding use/loads, say powering a home. Also chinese unbranded photo-voltaic material in general, like inverters, tend to be extremely inefficient.

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if I remember, at some point you had connected the 7809 with a load, but without connecting the GND pin. This certainly damaged the regulator.

True. But I did purchase a couple and the second behaves similarly. Still, it does look like it had a sink applied before. Perhaps it's not new.

Anyway, I will scrap both have experiment with more. No worries.