Thanks for your response Roy.
?
?Is the instrument frozen after that?
No, the HP4285A is always responsive.
?
Can you get to the 'CATALOG" page?
Yes.
?
The EEPROM failure is in the HP42851A Precision Q Adapter, not the HP4285A Precision LCR Meter.
?
There was a service manual for it; but, I don't have it.
?
I joined this group because a kind soul has uploaded the service manuals for the 42851A here :)
?
?
As best I can tell, the EEPROM chip in use in the 42851A is the NEC D28C64ACZ-20. It is the only non-74LS chip on the board. I assume it contained factory calibration data.? I checked the 5V rail inside the 42851A and it is reading 4.8V.
?
It looks like the EEPROM may be available here: https://www.utsource.net/itm/p/1158581.html?srsltid=AfmBOoqZq_Mzo4eOg7K5GqlcazQzkq6wlIruzsF7ukr1EaxzX_icP7NS
?
