[Elecraft] K2 100 watt PA problem

[Richard Haendel]

I am almost finished building the KPA100 amplifier. Presently I am on
Page 47 of the K2 Appendix G 100 W stage and RS-232 (K2/100) Ref F
October 7, 2009. 

Pg 47 Left column.  All voltages check OK. 

Pg 47 Right column under Receiver tests:

Step 1. Plugging in headphone jack to the K2, I get audio. 

Step 2. Plugging in KPA 100 (J5) into the K2 internal speaker jack I DO
NOT GET audio from the KPA100 speaker. Suggestion is that I have an open
or short. However: 

Step 3.  No audio from KPA100 speaker. If I disconnect the ribbon cable
between the K2 and the KPA100, I get audio from the KPA100 speaker.
What am I doing wrong.

Rich W3ACO (K24023).