Lots to love about this precision boat anchor. 1000V dc precision DC voltage standard and NIXIE tubes combined with proper clicky rotary knobs
Manual is here
http://www.hparchive.com/Manuals/HP-740B-Manual.pdfAnd some early references to it's predecessor the 740A (without the Nixies
) to it here
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1965-05.pdfApplication Notes on the use of 740B and 741B (** Worth a read for everyone)
http://hpmemoryproject.org/an/pdf/an_70.pdfSo why buy it - because I stumbled on it on evilbay and it looked very neat and tidy. Price was reasonable so punch the button and wait.
First photo below reveals an unhappy surprise on opening the package
Second Photo after a few hours warm up helped me smile as the 50 year old + Tracked my 34401a and month old 121GW to the last digit on the 10V range. The 100V and 1000V ranges are out of Cal but not horribly (under 10mV at 10V)
The tougher part of the purchase was to try and find the unobtanium input and output boxes and leads. CUBDRIVER has been looking for the input Box for a few years for his but seems I tin potted one 3 days after buying my 740B and snagged that too. Sorry again Pat
So anyone knows of a source of these Pat needs an input one and I need an output one.
Plenty more photos and full teardown to go including some metalwork fixups, calibration and possibly modding the high voltage inlet and outlet plugs to handle the 1000 VDC. There is a Mercury 1.35V cell to arrange a stable replacement for as well.