[volt-nuts] Valhalla 2720GS

JF PICARD jfphp at yahoo.com
Fri Dec 30 22:27:07 UTC 2011

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 !

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