[volt-nuts] HP 3458A repair.

John Phillips john.phillips0 at gmail.com
Tue Sep 17 16:36:06 EDT 2013

I have a 3458A that we sent to Agilent for calibration which it failed.
Before we sent it we calibrated it and it looked good to us. The infor. we
revived led us to believe that the cal memory may have caused the failure.
 We ask that it be sent buck to us and paid half the cal charges (about
$800) insted of the $2660.64 they wanted to repair it. We were just going
to repalce the ram in try again.
When we got the meter back it came with befor and afer data Like before 10
volts read 9.9999957 and after it read 10.00009 so they did something or
the meter drifted that much.
The problem is  0.1 volt and 1.0 volts failed at 8 and 10 MHz but passed at
4 MHz.
4MHZ 0.1 volt reads 0.097251 Lower Limit is 0.095930 PASSED
8MHZ 0.1 volt reads 0.085712
Lower Limit is 0.0959
10MHZ 0.1 volt reads 0.75569 Lower Limit is 0.084900 FAILED

4MHZ 1 volt reads 0.97272 Lower Limit is 0.95930 PASSED
8MHZ 1 volt reads 0.86389
Lower Limit is 0.95920
10MHZ 1 volt reads 0.73514 Lower Limit is 0.84900 FAILED

The AC after readings are the same. I do not see how AC after could be that
identical even if they did not try to calibrate it. Did they just copy the
before data and call it after data?

My best guess is that if the 4 MHz is in and the higher frequencies are not
the meter requires some kind of mechanical adjustment to get the frequency
response   withing spec or the AC board needs to be repaid.

Are they charging a standard repair charge to do a calibration? I do not
see changing the memory to fix this.

Where would you go from here if this was your meter?

John Phillips

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