With this meter reading, enough to know Fuse is the culprit?

[riotubes]

Current project is dac with tube output. Went to measure secondary voltages...all in the mV range. The power pathway is:

iec hot to fuse IN => fuse OUT to switch => switch load to hot primary leads

iec neutral goes straight to neutral side of primaries. iec ground to earth

I'm measuring:
- 121V at the IEC inlet.
- 121V at the input of fuse, BUT

- 5 mV at the Output of fuse
- 5 mV at the in and out of swtich

This is my first build. Can I safely deduce that I need to replace the fuseholder (using 3amp fuse btw)? Maybe I overheated it when soldering the hot leads from iec?

Feedback appreciated!

 

[poobah]

yep...

With EVERYTHING unplugged and the switch off; you can measure the resistance of the fuse. It should be much less than 1 OHM.

🙂

 

[Enzo]

And another way is to unplug the unit, and measuer resistance between teh two main prongs of the power plug - or your IEC. With good fuse and switch ON, you will essentially measure the primary winding of the power transformer, whatever resustance that might be.

If you get an open eradung, move from element to element to see where continuity is lost.

 

[riotubes]

Thanks Poobah and Enzo. The fuse holder was the culprit. I replaced it and measured appropriate voltages for all secondaries.