Editing PDP-10 Power System Service (section)

== KA10 supplies and margin checks ==
The KA10's power supplies are bolted to a hinged frame inside each cabinet's rear door.<ref name="ka1" /> The system logic runs from +10 V and −15 V. The margin check system replaces these fixed voltages with the output of a Type 702 variable power supply: the five-position MARGIN CHECK switch on the maintenance panel selects the polarity of the margin voltage and feeds it to the left or right side of the system, and local switches beside each module panel select the +10 V or −15 V margin for that rack. The margin check meter reads the voltage applied to a panel accurately if margin switches are on in only one area of the machine.<ref name="ka64" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''KA10 margin limits (DEC-10-HMAA-D Table 6-4, extract)'''
! Panels !! +10 V margin, high !! +10 V margin, low !! −15 V margin, high !! −15 V margin, low
|-
| 1A, 2A, 2M || +12.0 V || +8.0 V || −17.0 V || −13.0 V
|-
| Other panels in bays 1, 2 and 3 || +17.5 V || between +2.5 V and +5.5 V, depending on the panel || −18.0 V || −12.0 V
|}
<ref name="ka64" />
DEC's table gives the limits for every panel, with special values for panel 1S during tests D, L and M and for the reader lamp supply in bay 3; use it when margining a particular rack.<ref name="ka64" /> Switching margin switches while a program runs can cause transients that alter registers or start a memory cycle; DEC's procedure is to press STOP, examine location 0, set the switches, press RESET, set the address switches to 4000 and press START.<ref name="ka64b" />