HP 2113B service manual / schematics

Hi All, I'm in the process of powering up a 2113B. I took a look at the output voltages from the PSU and they all look fine *except* the -2 volt line that appears to be running at -2.47 volts. I have the 2109B / 2113B installation and service manual but the service procedure just talks about adjusting the 5 volt line and all the other supply voltages tracking this one. I can't find a schematic for the power supply in the documentation that I have 02109-90015. Questions: 1. Is my copy of 02109-9005 (Installation and service manual) incomplete i.e. should there be a schematic in it? 2. Does anyone have a schematic for the 2019B / 2113B computer power supply. Note that the 'B' is important as the power supply was revised between the 'A' and 'B' models. 3. What is the -2 volt line used for? 4. Does it matter that the -2 volt line is outside specification? 5. Is a full schematic available for the 2113B computer? - I'm sort of interested in what exactly is going on on the motherboard. Many thanks Peter Brown