On 12/17/2017 08:24 AM, Peter Coghlan via cctalk wrote: >> I have a suspicion that this component may be faulty on the input side of my >> H7826 PSU. A little tester I have does not recognise it, it is possible that >> the currents it uses are too low for this particular triac, but I am not >> sure. >> > What is the function of this triac in your power supply? > > I have come across a triac which is used to switch between 115V and 230V input > in the PSU of a DEC 3000/300. My triac went short circuit which caused some > release of magic smoke when the PSU was used on 230V. I also had difficulty > finding a replacement for it so I ended up leaving it out. The PSU worked > fine on 230V only without it once I replaced the other damaged components. > > If your triac has a different function, ignore the above. > > Regards, > Peter Coghlan. >
OUTPUT CROWBAR: The common use is to create a hard short circuit across the output if the output voltage exceeds a safe limit. The logic is that a power supply is cheap compared to the rest of the computer. The typical output where this is done is the 5V rail. The tester likely cannot test a triac its not a simple transistor or diode. They are easy to test a light bulb (12V) and a DC source. Allison
