copied from Internet netnews:
From: kurt@cs.tamu.edu (Kurt Freiberger)
Newsgroups: rec.radio.amateur.misc
Subject: THE REAL Standard 558 radio mod  (1/2, diagrams in part 2)
Keywords: Standard C558A extended transmit

>From a sheet that I got from a vendor, here 'tis:

MARS/CAP (Wide band transmit)

1. Remove battery and antenna.
2. Remove front case assembly block by unscrewing.
3. Remove the copper plate around the back side of the display section.
4. Remove the diode indicated by D2, and add a diode 1SS301 leaving other
   components intact as per the following drawing.  (in part 2)
5. Reassemble radio and install battery.
6. Turn on power and execute master reset.

Kurt Freiberger, wb5bbw   kurt@cs.tamu.edu
==========================================================================
diagrams in part 2
Note: I haven't tried or verified this, proceed at your own risk.  And
do not transmit outside of legal bands!  WA2ISE
/EX