[Test-Equipment] B+K 1640 Mobile Equipment Power Supply question

[Bob Parnass, AJ9S]

Is there an adjustment pot or component can I replace in my
B+K 1640 Mobile Equipment Power Supply to calibrate
the front panel meter in voltage mode?

The supply works well, except the panel meter reads
low when set to read voltage:

Reading  vs. Actual

11.0   vs 12.6 actual
12.0   vs 13.7 actual
13.0   vs 15.0 actual
13.8   vs 15.8 actual

The meter is accurate when displaying current.
The problem exists only when displaying voltage.

I don't have a schematic and the service manual costs more
money than I want to spend.   Thanks!
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Bob Parnass, AJ9S               Linux User             http://parnass.com