Had chance to work a little on this sick box.
One of original binding post is busted, and unlikely that I'll be buying HP original replacement, so went with BNCs instead:
![](https://xdevs.com/doc/HP_Agilent_Keysight/4262A/img/rear_ibnc_1.jpg)
Pitch is not same as modern LCRs, but still useful with usual LCR cable probes.
Also replaced rear rusty BNCs with fresh new ones:
![](https://xdevs.com/doc/HP_Agilent_Keysight/4262A/img/rearb_1.jpg)
And X-cap:
![](https://xdevs.com/doc/HP_Agilent_Keysight/4262A/img/xcap_1.jpg)
Cleaned chassis, replaced original fungus coax wiring to brand new pieces.
Almost blown transformer by stupid mistake, but was quick enough to escape the damage
Meter power on as before, and quick PSU checks revealed absence of -12V (+188mV instead on it). So CPU does not get his -5.0V love and hence nothing works.
Supply -12V from Keithley 2400 SMU allowed LCR to boot, but fail selftest with messages FAIL 1 and FAIL 2.
Checked A9Q4, replaced A9R6 and A9C5 - still no -12V. Likely TO-3 2N3055 BJT is dead or LM741 opamp. Negative -12V is simple linear supply, tracking from +12V supply by 10K/10K resistors. Both resistors are OK. I don't have any high power BJTs to try, so will have to wait to get new one first.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
Also discovered that 4261A is very similar box, with most of analog boards same as 4262A. PSU A9 board is even labelled same.