HP 8648C with low output

[mmaseda]

I have a HP 8648C signal generator with option 1EA (high output).  At 100 MHz I can only get 14 dbm out.  Manual says I should get out around 20 dbm.  Power also seems to be low at other frequencies.  I’ve already checked the attenuator and RPP modules and they appear to be fine.  Any idea where I should check next?