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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Bias gauge posted by 2395 on December 2, 2024 at 03:37:20:
I used a 1mA meter with a shunt for full scale deflection of 100mA. The small shunt resistance diverts nearly all the cathode current around the meter. I also fused the cathode and added a Zener to prevent cathode voltage from going too high if the fuse opens.In my case, the meter measured 90Ω. The formula for the shunt is:
Shunt R = Meter R divided by (n - 1) where n is the multiplier.
Note that high sensitivity meters can be damaged if you attempt to measure them directly with a VOM or DMM. For example, my DMM outputs about 0.5V on the "non-diode" scales. That would result in an over-current of more than 5mA with the panel meter I used. Here's how it needs to be done:
To answer your question more directly, the meter is mounted on the front panel in my monos, and I leave it active all the time. It's reassuring to know the output stage is operating as intended. :)
Edits: 12/02/24 12/02/24 12/02/24 12/02/24 12/02/24 12/02/24
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Follow Ups
- Here's how I did it - Triode_Kingdom 10:51:12 12/02/24 (1)
- Why did you use the Zener? - Ralph 13:50:06 12/13/24 (0)
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