UPDATE: Problem resolved, repaired and working as it should.
First, I fluxed and reflowed all of the pwr. transformer connections on the board. As suggested, I have found units of this model with bad /cracked solders on the transformer in the past. In those cases, the display was blank or intermittent.
Next I checked the low voltage power supply rails and found that C605, 470uF, 50V electrolytic capacitor was open. Changed that cap and now all works perfect. All 21 self test show no errors, DC volts zeros when inputs are shorted, etc.
Many thanks to giosif, xwarp and bdunham7 for taking the time to give me good advice.
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