This applies to all Production K2's (S/N 101 and above).
[Field Testers please see below]
 

We have been notified in two cases that K2s were shipped with incorrect BFO crystals.

Please check your K2 to make sure the BFO crystals (X3, X4) are marked '4.91-S'.

If they are marked 4.91-20 they are incorrect. In this case first check X5-X11 to make sure you have not installed the '-S' crystals there by mistake. (X5-X11 do use the '-20' crystals.)

If you determine you have received the 4.91-20 crystals for your BFO, please email us immediately at radios@elecraft.com and we will send you replacements.

Explanation:
The 4.91-S crystals have a slightly higher resonance frequency then the -20s, which allows the BFO to be pulled high enough to position it properly for both USB and LSB through the wider filter used in the SSB adapter.

Using -20s for the BFO will NOT impact CW operation, as it does not require as much of a BFO shift. It is OK to use the -20s while you are awaiting the replacements.

Field Testers:
All original K2 Field Testers had -20 crystals for their BFO. Those who have ordered the SSB option will receive new '-S' BFO crystals. There is no need to change them prior to receiving the SSB option.