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Originally Posted by busterb
Tw. Belive it or not but I went to electronic school years ago. And have maybe more meters laying around than most folks. Meters lie. How many people think even know how to calibrate there meter? Are you telling me that the tester doesn't simulate a load? Well maybe not, but my son said was bad. I said no because I've taken readings w/voa meter. Anyhow a new PS fixed it.
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If a tester provided a significant load, then tester would be too hot to handle with comfort. It would be a 300 watt hot plate. Testers apply minimal load to meet startup requirements for power supplies (some - not all - supplies need a minimal load to operate).
Yes, meters do not necessarily report RMS voltage: they lie. But that is what makes many meters so good at identifying bad power supplies. Again, note numbers provided because of how meters typically work.
I am more than just a tech. We designed power supplies even in the 1970s. Have even demonstrated on a system that was intermittent - the supply was not providing power as claimed. System would boot and mostly work. And then we put a meter on it. Quite obvious that a clone power supply could not service the load - even though the owner insisted supply was replaced and now working. Meter demonstrated otherwise. Been doing this stuff for too many decades. I prefer an oscilloscope because it says faster what I want to learn. But the meter is how field problems are identified or eliminated quickly as a suspect.
A $15 tester, among other things, does not provide a sufficient load for testing. It can declare a power supply bad but it cannot declare a power supply as good.
BTW, one final point. Notice that tester did not get hot and did not contain fans. Fans would be required if tester sufficiently loaded a power supply. Just another reason why power supply is best tested (and tested faster) still inside the computer. Just another example of why 'learning why' makes those meters a so superior solution.
BTW, do you still have a VTVM? I have a wee bit of knowledge and experience.