[volt-nuts] New HP3458A

[Jason Watson]

I've also seen excessive Guard to Low leakage when varistor RV501 has gone
bad (it's located on the front/rear switch pcb and it's possible to replace
it while leaving the circuit board in place if you are careful).
 HP/Agilent/Keysight Part number is 0837-0196, cross referenced to a Harris
Corp. V430MA3A.


On Fri, Aug 15, 2014 at 10:46 AM, Stephen Grady <grady.steve at gmail.com>
wrote:

> Randy,
>
> I have come across a few 3458A's that had leakage between Guard and Low
> when
> te guard is in external guard position. This was due to a leaky external
> guard switch and/or leaky front rear switch. This can be quickly determined
> by measuring resistance between guard and low with guard external. This
> normally in not an issue except when you are using 3458A to measure voltage
> with low above earth potential say in a bridge the guard low leakage will
> be
> loading other arm of the bridge.
>
> Kind Regards,
>
> Steve Grady
> Sydney, Australia
>
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of Randy Evans
> Sent: Friday, 15 August 2014 1:22 PM
> To: volt-nuts at febo.com
> Subject: [volt-nuts] New HP3458A
>
> I picked up a used HP3458A today, which I needed for some precision DC
> measurements i need to make. It passes all the self tests and the Auto Cal
> but is there any thing else I can check ( I have a 14 day RR).  It reads a
> 10V standard I made within a few tens of ppm, but it's not a 732A but that
> is at least comforting.  It also reads an ESI 10Kohm standard resistor dead
> on.
>
> The only problem is that the display has some faint pixels in some
> locations, with three in the second row for every digit location dead.
>  Likely a pixel driver I would think.
>
>  I am not too familiar with it yet but I noticed when I push the auto zero
> button, the display has a blinking square until I hit a measurement mode
> button; e.g., DCV, ACV, OHM, etc.  Is this normal?
>
> Regards,
>
> Randy Evans
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