[Elecraft] K1 Tranmsmit Problem

[George Davis]

Earlier this year I built a second K1 with 2 band filter board.  Bands 3.5 and 21 MHz.    Band 1 (3.5 MHz) has no problems but I get no output on band 2 (21 MHz).  I have two filter boards (different frequencies) and another K1.  Both filter boards are fine in the old K1 but neither gives any Tx output on band 2 in the new K1.  I have been trying the "Transmitter Signal Tracing" procedure on page 6 of Appendix of the manual. All the voltages are much lower than the expected values, typically less than a quarter of the expected figure. This with either band selected  BUT it works perfectly on band 1.
Any help will be appreciated.

George.  G3ICO.