[volt-nuts] FET HP3456A

[Tony Greene]

I have been troubleshooting a HP3456A voltmeter.  

Its giving a stange fault, but I beleive I have nailed it down.  The unit is reading +10.00000 volts input at +9.99661 volts.  If you reverse the input, it reads correct at -10.00000 volts. All other ranges read correct on either polarity.

What I need is a source for the FET  A20 Q109 or a suitable substitute.  Its HP part number 1855-0298, it was made originally by USA mfg 02883 - Siliconix, Inc, Santa Clara, CA.  It crosses to NSN 5961-01-135-1324.  And Vishay has bought them and the part number is now obselete.

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