Well, I'm even a
1st EloPrfGerMech (w/o electro) from the German AF
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
. All the stuff I repaired and calibrated in 1980.. 1982, was all electric, though..
The EARAM needs a -30V programming voltage, which is generated by a charge pump on A5, Floating Logic board. C804 was a 47µF, 50V electrolytic made by Philips, which had 3nF left only, so not delivering sufficient current anymore for the erase/programming cycle. I assume, that this killed the content of the old chip, not the chip itself.
Owners should check / replace this capacitor with 100µF/50V (which I have seen in other units).
In the service manual, chapter 8, Monitor, Calibration and Self Test, there are hints how to access (read) the EARAM Nibble by Nibble, using the MONITOR via RS232, and this should be done for the whole 1024 Nibbles, (2 pages of 256 byte of cal data) to copy the calibration constants plus the parity checksum.
There seems to be the facility to write back this low level storage information also, as there is no GP-IB command to write back the real numbers to EARAM.. similar to the 3458A, where you can only dump the calibration constants, but not write anything back from outside.
The manual is not precise at all how to do this exactly, and I did not try any more.. I had a lot of trouble with the interface programming - Handshake / Arming and Triggering methods seems to be implemented quite unstably, compared to hp instruments.
Anyhow, a quite nice instrument for its time, and still very stable, electrically..
There had been several of these in our stock @ RWTH Aachen 2. Phys. Institute, and my prof. initially requested me to overhaul and use these .. but I was very happy to instead purchase the new hp3458A in 1989.. due to being a bit faster ...
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/cool.gif)
Frank