[pjchappy]

I have an isolation transformer that developed a higher-pitched hum and a surge suppressor (Tripp Lite Isobar) that developed a high-pitched whine around the same time.  Each one is used on a separate 20-amp dedicated circuit.  What could have caused this?

Please let me know if you need any more info.

Thanks,


Paul

[Speedskater]

Is the whine & hum 24 hours a day, 7 days a week?
Can you take the units to a distant friend's (mileage wise) house and check then there?

[pjchappy]

Yes, 24-7. 

I can, but not for awhile.

I do have a multimeter.  Let me know if there is anything I can check with that.

Thanks again,


Paul

[jtwrace]

Can you take the units to a distant friend's (mileage wise) house and check then there?

Take it to work!

[pjchappy]

In the meantime, any ideas on what could possibly be causing this?


Paul

[pjchappy]

Just a bit of additional information:  I put a different/new surge suppressor (another Tripp Lite Isobar) on the circuit where I previously was using the isolation transformer.  This new surge suppressor also has developed the same whine as the surge suppressor.


Paul

[jtwrace]

For giggles have you put a DMM on this line?  Voltage seem normal?  Also, have you checked the DC?  I'm just asking to make sure it's not something really really waaaay off. 

Have you plugged any of these units into a different circuit in the house?  Any difference?

[Folsom]

DC is big for making trannies hum.

[Speedskater]

With your meter, carefully measure several of the circuits in your home.  Do they all measure about the same? (within a few volts)

Look out your windows,  do you see anything that wasn't there before all this started?
Are there any commercial or industrial building nearby?

[pjchappy]

Will do more with the multimeter this weekend.  Did check the voltage on one of the outlets and had a steady 121 volts.  Switched to measure DC and there was a fluctuating amount that was measured (forget the numbers).  However, it is my understanding a multimeter cannot accurately measure DC on the power line.  Is this correct?

As far as anything new in the area or a commercial/industrial building nearby. . .no, there isn't (commercial area within 1/2 mile or so).


Paul

[Speedskater]

Will do more with the multimeter this weekend.  Did check the voltage on one of the outlets and had a steady 121 volts.  Switched to measure DC and there was a fluctuating amount that was measured (forget the numbers).  However, it is my understanding a multimeter cannot accurately measure DC on the power line.  Is this correct?

Paul

Yes, that's true.  It's kind of tricky to measure DC on an AC power line with an average multi-meter.  But in most cases it's not true DC but a DC off-set caused by harmonic distortion of the AC power.  It's like in the old Cool-Edit Pro digital audio program, you could measure the DC off-set of music.