Hi. Nearing completion of the PSU for my valve phono stage. The primary fuse will see both heater and HT current, I'm using a 1.6A fuse to start with, May have to go to 2A.
I measured the resistance through the fuse at 2ohms, though I strongly doubt the accuracy of my multimeter at that level.
If 2ohms is correct, then at 2 A the fuse would dissipate 8W...? Can that be correct? Seems surprisingly high to me.
I measured the resistance through the fuse at 2ohms, though I strongly doubt the accuracy of my multimeter at that level.
If 2ohms is correct, then at 2 A the fuse would dissipate 8W...? Can that be correct? Seems surprisingly high to me.
The fuse will read almost zero. It is your multimeter leads playing games.
I have just built and tested an RIAA pre-amp with Baxandall tone controls. Uses two ECC83 and two EF86. Very quiet, very high gain from the EF86 and I use a 125mA Time Delay fuse which is quite sufficient.
I have just built and tested an RIAA pre-amp with Baxandall tone controls. Uses two ECC83 and two EF86. Very quiet, very high gain from the EF86 and I use a 125mA Time Delay fuse which is quite sufficient.
The fuse will read almost zero. It is your multimeter leads playing games.
I have just built and tested an RIAA pre-amp with Baxandall tone controls. Uses two ECC83 and two EF86. Very quiet, very high gain from the EF86 and I use a 125mA Time Delay fuse which is quite sufficient.
Thanks Jon - yes I did wonder. it's getting on a bit (and was a cheapie), might think about buying a newer, decent quality one if I see a bargain somewhere.
Rh,
what does you ohm-meter read with the probes touching?
That reading can be subtracted from any resistance reading you take across other low value resistors.
A very few DMM do this subtraction electronically when you "set up" the ohm-meter.
It varies between switch ons, sometimes up to 20. I've changed the battery and reseated the plugs, but it still varies.
Not to worry, I only measured the fuse out of interest. I think I'll keep an eye out for a decent MM on sale.
testing a fuse non destructively with any meter is a go nogo type of test for us mere mortals. generally the 'buzz out' mode is sufficient on a decent DMM for debugging bad AC connections. edit > reminds me of the Bugs Bunny cartoons> testing bomb fuses on a conveyor belt with hammer blows .
what's a MM /moving meter?
if you haven't used a meter in a long time replace batteries and test the meter 1st.
what's a MM /moving meter?
if you haven't used a meter in a long time replace batteries and test the meter 1st.
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a new DMM should have resistance scales from 199.9 ohms to 19.99Mohms, 199.9mVac to 600Vac and 199.9Vdc to 1000VdcIt varies between switch ons, sometimes up to 20. I've changed the battery and reseated the plugs, but it still varies.
Not to worry, I only measured the fuse out of interest. I think I'll keep an eye out for a decent MM on sale.
Any others are just for guides and are rarely accurate. I don't place any value on them.
But handy if they offer continuity buzzer, hFE and capacitance
A basic DMM offering 199.9Vac can be found in the UK for <<£10.
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