I have a good one and another that needs some help. The relays on the nullmeter board seem to be the main failure item on these. One thing you have to note in the manual is that it states that you have to be sure that the nullmeter reads POSITIVE if the 2720GS' output is HIGHER than the divided standard. Maybe that's where things went wrong? I haven't been successful in getting anything from Valhalla, but I've read about the hidden button and its backup calibration as well as the necessary password. I don't know why they didn't just put the default password in the service manual. It'd be great if anyone can find this out and post it! Chris Erickson >Hello, >? >I have?bought? two months ago a Valhalla 2720GS but I am desesperate and the list is my last hope. Contacting Valhalla >gave no results (it is a 20 years old product no longer supported...) As I received the calibrator, it passed all tests, >calibrated itself... and outputed 1, 245....V for 1V indicated, 10,2... for 10V and so on, mesured with a 3458A and a >41/2 digit volmeter (just in case the 3458A was down !). The mesurement of the output with the nullvolmeter was worse >(if worse is possible) and using the nullvolmeter to drive the calibrator, as indicated on the manual, gave absurd >results. What a pity... >After?a day running and?3 or?4 cal of the nullvoltmeter, the calibration of the nullvoltmeter failed once, then?passed ?>but finaly the nullvolmeter failed : at start, "Nullvoltmeter fail" "Repair nullvoltmeter"?with long beeps. The >calibrator itself is always passing all tests, calibrating itself and false as usual ?I have spent several?days on this >nullvoltmeter?discovering the delights of floating supplies,?testing everything, analog to frequency converter, quick >overload mecanism, opto isolators, closing and opening the relays with floating pulses, using a tek isolator A6902B for >the scope...nothing. It is always stuck with the overload relay closed. I guess that the X2210 NVRAM does contain not >only the cal constants but the basic program seen by the CPU. (I have changed it copying the old one). Does anybody have >an image of this Xircor EEPROM ? >? >According to?the service manual there is a hidden front panel key enabled when you turn the front pane key for >calibrating the 2720 from an outside reference?: it gives the oportunity to reload the factory cal constants but it asks >for a password and you have to contact Valhalla for it , Trying some basic combinations like those used by HP gave no >result. Does anybody get an idea ? >? >Thanks a lot !