[Elecraft] K2 - 14.2 V for internal battery?

[Tony Wells]

Folks,

Can you help? I need to charge my internal battery but can't get the PSU
voltage up enough. I've got a "CB" EPS-1012 linear supply rated at 13.8V
that actually delivers 13.3V. Clearly I need to bump up the voltage a bit.
However I can't get hold of the schematic for the PSU.

 I'm sure it is a "classic" circuit, using  2 2n3055s and what looks like a
T03 regulator - the make and part number has been scrubbed off. It also has
a Zener which measured I think10.5 V when I had the lid off.

If I added an ordinary silicon diode (or led) of 1.2V drop in series with
the Zener would that bump up the voltage sufficiently?

Thanks

Tony