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General Category => General Discussion => Topic started by: Moodyhh on October 12, 2023, 10:10:24 PM

Title: Eros2 Power Supply Voltage Check
Post by: Moodyhh on October 12, 2023, 10:10:24 PM

Hello All,

At the 6.3 Volt terminal point on the Power Supply circuit board, I’m getting 6.25 volts - is this considered acceptable?  At the + / - 275 points I’m getting 375.7 volts.

Thanks,
Moodyhh

Title: Re: Eros2 Power Supply Voltage Check
Post by: Paul Birkeland on October 13, 2023, 05:14:34 AM

Yes.

Title: Re: Eros2 Power Supply Voltage Check
Post by: Moodyhh on October 13, 2023, 05:39:53 AM

Thanks!

Title: Re: Eros2 Power Supply Voltage Check
Post by: Moodyhh on October 13, 2023, 05:42:00 AM

What can cause these minor variations, or was the 6.3 figure just a ballpark to begin with?

Title: Re: Eros2 Power Supply Voltage Check
Post by: Paul Birkeland on October 13, 2023, 05:52:31 AM

The tolerance of the resistors mounted next to the voltage regulator, as well as the accuracy of your meter.

Title: Re: Eros2 Power Supply Voltage Check
Post by: Larpy on October 13, 2023, 06:02:13 AM

Operationally, 6.25 volts is just fine.  I've built a fair amount of tube electronics over the years and I don't ever remember measuring exactly 6.3 volts on a tube's heater.  For most tubes, anything within 10% is acceptable, so that means anywhere between 5.67 and 6.93 volts is OK, but I prefer to be within 1-2%.  Which you are.

As PB pointed out, the precision of the dropping resistors plays a role on what voltage you get.  So does the AC voltage from your wall outlet.  Nominally, it should be 120 volts where I live (the U.S.), but it's common for many of us to see it a bit below or above that.  I imagine it's the same in the rest of the world as well.