Multiple months has been under my bench waiting for repair, so lets started.
Meter is quite old ( according to serial number made 1995 ).
This meter is quite popular for ration measurement compare to 34401A it has low voltage preamplifier which enable 1mV DCV range and low ohm measurement with high precision.
- 7½ digits resolution
- 100 pV, 100 n? sensitivity
- 1.3 nVrms, 8 nVpp noise performance
- Built-in low noise 2 channel scanner
- Direct SPRT, RTD, Thermistor, and Thermocouple measurements
Thanks to absence of fan unit is clean after several years in operation.
Compare to competitor (Keithley 2182A Nanovoltmeter) has own current source which enable Ohms/RTD measurement.
Meter is still in active production (end of this year will be not possible to ship to EU - RoHS)
Price $4445 new one, $1538k unit exchange by
Agilent Keysight. Used working unit can be found on eBay for quite high prices ( similar to 3458A), working unit in uknown state should be about $500, with calibration $700-1k.
Like 3458A it has been sold by Fluke as
http://assets.fluke.com/manuals/hp34420xiseng0000.pdf for temperature measurement and calibration.
Initial inspection:
- Power on and passed self test
- VFD display is little bit dim
- Input connector has bend pins
- DCV channel 1 - not working
- DCV channel 2 - OK
- 2W Ohms - OK
- 4W Ohms - OK
- RTD - OK
Schematic:
http://www.ko4bb.com/manuals/download.php?file=HP_Agilent/Agilent_34420A/Agilent_34420A_SCHEMATIC.pdfUser Manual:
http://literature.cdn.keysight.com/litweb/pdf/34420-90001.pdf?id=1000003601:epsg:dowService Manual:
http://literature.cdn.keysight.com/litweb/pdf/34420-90010.pdf?id=816987When I tried to fix bend pin I found they are made from pure copper ( not like the regular gold plated LEMO pins ) and are quite brittle
So I needs to order replacement.
Replacement we discussed
https://www.eevblog.com/forum/repair/looking-for-the-input-connectors-for-agilent-34420a/and after this excersise I can confirm that the connector housing is EVP.1S with custom made pins.
I do not want to stop repair by this, so I desoldered connector assembly and solder insted of it 50cm of PTFE insulated silverplated wires (made by Habia).
After repair meter can be handy for low EMF measurement and ratio measurement of LTZ1000 boards.
Any experience with DCV Channel 1 repair may be helpful.