[volt-nuts] 3458A resistance calibration

[Todd Micallef]

I just read your post again and missed that you reflowed the solder joints.
I will have to stop reading posts with my phone.

Todd

On Wed, May 20, 2015 at 3:52 PM, Todd Micallef <tmicallef at gmail.com> wrote:

> Frans,
>
> I had two 3458a fail that resistance cal. I eventually replaced the
> front / rear switch. The easy way to test it is to measure the resistance
> with the front panel jumpered and then short the internal  black and white
> cables at the A1 board and measure the difference. I also had one with a
> bad cable in addition to the switch. The cables develop small breaks just
> behind the crimps. Wiggling the cable showed how bad it was. Both were
> available for order the last time I needed them.
>
> Todd
>
>
> On Wednesday, May 20, 2015, Electronics and Books via volt-nuts <
> volt-nuts at febo.com> wrote:
>
>> my 3458 was getting troubles with the calibration of the zero. As volts
>> where no problem and ohm were pretty accurate, my conclusion was that there
>> is basicly nothing wrong. the calibration stopped at the ohm-10. so it must
>> be in the sense lines somewhere. on de dc print there where 2 big resistors
>> (Dale ?) in the sense lines. with a magnifying glass i could spot litle
>> cracks in the solder. after heating with some fresh solder the fault was
>> over.
>>
>> i have red several times that the standard resistor for ohms should be of
>> a better type. In my 1998 production unit it is a vishay vhp101 40k. that
>> must be one of the better ones that were made by vishay. in an older 1994
>> unit there was no brand or recognisable type code on it.
>>
>> Regards
>>
>> Frans
>>
>>
>> info at ElectronicsAndBooks.com
>> Netherlands
>>
>> Discere ne cesses
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>