I have bought two 12VAC (i.e. 240V AC to 12V AC) adapters from two different sources (they are different manufacturers).
They have the removable plugs, so when I use a multimeter with one lead into the power output hole and the other lead into the ground hole, I get a short (or about 2ohms of resistance). This is all without the adapters connected to anything (unpowered and all).
When I do this same test for a 12VDC adapter, there is no continuity. It is a few k's resistance which rises.
Can someone explain to me if this is normal for AC power?
The reason I am concerned to hook this up to a diy PSU that I built (which the instructions say that it runs on 12VAC and specifies clearly that I must use an AC/AC power supply), is because when I first hooked up the first 12VAC adapter, a large 4700uf electrolytic capacitor started smoking and leaking. Note that the circuit was still working during this (the LED display was still on and functioning). The interesting thing was, before I bought the AC adapter, I was using a 12VDC adapter which did not cause any problems and the circuit was actually working. After removing the capacitor, I noticed that there was a short between +12V and ground. This was when it was powered off (I didn't dare power it on again).
At first I suspected that it may have been a faulty AC adapter; then, I feared that something in my circuit may have damaged the adapter causing the short. When I bought a second 12VAC adapter from a different source, I discovered that this also had power shorted to ground. I still have not dared to power it on.
As I replaced the 4700uf capacitor, I realised that I may have had it the wrong way around, which explains why it blew up. I do not understand why when I was using the 12VDC adapter, that it was actually working and nothing blew up.
I am still too afraid to power it on for fear that it may blow up, until someone explains to me whether it is normal for an AC/AC adapter to have continuity between power output and ground (I cannot for the life of me find any information about this online and this can't be a coincidence with both AC/AC adapters from two different manufacturers).