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Is it normal for ammeter on 6674A to change as voltage changes with no load?

Question asked by drkirkby on May 16, 2016
Latest reply on May 18, 2016 by drkirkby

As you may have noticed from another thread, I had a non-working 6674A (option J06, 70 V @ 30 A), which I have now got working, although some of the capacitors don't look in great shape, so I don't suppose it is meeting all the specifications. But at least from the front panel it responds as expected.

 

Anyway, something I have noticed, that I have never seen on any of my other Agilent/HP 66xx series power supplies is the following.

 

With no load on the 6674A PSU, the ammeter reads virtually zero as expected.  If the voltage is changed, there's a change in the ammeter. It is hard to read how much it is moving by looking at the digits rapidly changing, but I think somewhere in the range 100 to 200 mA. Then it settles back down to almost zero in fraction of a second.

 

I assume this current is due to some capacitors being charged./discharged as the voltage is changed, and is nothing to worry about. Can anyone confirm if this is so? I have a number of HP/Agilent 66xx power supplies,  but have never noticed this before. But the 6674A is the most powerful (2100 W) of any I own.

 

Dave

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