[volt-nuts] HP 3458A repair.

John Phillips john.phillips0 at gmail.com
Wed Sep 18 11:45:13 EDT 2013

The meter will be here in a few days. I did buy the ram. As far as the
meter age goes, unless it is a very old hardware revision, I would rather
have an old meter because it is more stable. That is until it brakes.

I do have before and after readings and the 4 readings are the only ones
that failed. The after readings are better than the before readings.
Because the 8 and 10 MHz failed we did not get a certificate but we do have
a good limited calibration up to 2 MHz. Just no official cal.

The cal we wanted was $1600. We will still have to pay that after the
>From what I can tell they did not run SCAL or the before/after readings
would not have matched. Like they really did not run after readings or
there would have been some mismatch.

On Tue, Sep 17, 2013 at 6:50 PM, J. L. Trantham <jltran at att.net> wrote:

> John,
> Can you give us more information?  Serial number, Rev. number, CALNUM?  How
> much to invest will be determined by age and other condition.
> It doesn't sound like a simple CALRAM issue but changing the CALRAM is
> relatively easy.  I removed all three DALLAS chips in mine and installed
> sockets.  The CALRAM can be read with a chip programmer and the data
> written
> to a new DALLAS chip.
> I would also call Gary Bierman at the Loveland Cal Lab and have a long talk
> with him.  He has a lot of insight into these meters and generally prefers
> to do a component level repair rather than an assembly level repair.  The
> charge sounds like their standard repair charge, no matter what the problem
> is, and includes a 'fresh calibration' along with a warranty, a year I
> think, but Gary will be able to answer that question.
> Also, once you get the meter calibrated by Agilent (and thus prove it is
> functioning normally) it will be eligible for their 'repair agreement'
> which
> is $178.68 per year.  I would consider buying a 5 year agreement after the
> repair.
> Good luck.
> Joe
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of John Phillips
> Sent: Tuesday, September 17, 2013 3:36 PM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] HP 3458A repair.
> Hi,
> 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
> 2
> 0
> 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 FAILED 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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John Phillips

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