My KPA1500 is giving me trouble with Fault: Low Gain Ratio-1, Ratio-2 and Ratio-5. 
This is at low temp 28C on the low bands.

Anyone know what this means? I sent a note to the factory twice but no reply.

The amp works on 6 meters but at reduced power.

73, Wayne N2WK

HI, Wayne.  The Low Gain Ratio faults can be quite serious events in the KPA1500, and I would strongly suggest not continuing to use the unit on 6-m or any other band, even at reduced power.  Elecraft will reply with its expert advice, soon.

In the interim, if you wish to read more on this, go the the above "Search" button and enter "LOW GAIN RATIO" (without the numbers) to learn what others have said and done.  I wish you well,
// Mark 
.. w2or ..