I am looking for the service manual of the Datron Wavetek 4910. I have just got this reference standard from Ebay : is it normal to see 3 cells at 2 or 3 µv under 10V and one at + 13µv (23°C with 3458A just calibrated yesterday) or it is an obvious problem with the cell (the third one) ? What is the reference of the replacement batteries ? Thanks.