ELECRAFT K2 BUILDER ALERT #19
Current Metering (C42 and C44)

Applicability
Revision A and XC K2s: ALL
Revision B K2s: Serial Numbers 3000-3077


Background

This builder alert replaces alert #17 -- PLEASE READ.

Builder alert #17 had recommended the addition of C44 (0.1 uF) to the Control board on older K2s. This capacitor is also present on the revision B K2. Based on further testing and field reports, we have determined that C44 should NOT be used. In some cases it can cause current-measurement inaccuracies of as much as 25% at transmit currents of 2 amps or higher.

Alert #17 also mentioned increasing the value of C42 to 0.1 uF. This change is still required on older K2s. Revision B K2s already have the correct value of C42.


MODIFICATION INSTRUCTIONS

If your K2 is revision B (s/n 3000-3077 only):

- Remove C44 on the Control board. (On Rev A boards, C44 is located on top of and bridging R7. On the rev B
board, C44 is located between U1 and P2.)  NOTE: This is already specified on the errata sheet for revision B K2s starting with serial number 3078.


If your K2 is revision A or XC:

- If you added C44 previously (alert #17), REMOVE IT.

- If you did not increase C42 (alert #17), do so now.
Use an 0.1 uF or larger ceramic or monolithic capacitor (not electrolytic). If you don't have any suitable capacitors, send a request to
parts@elecraft.com and request P/N E530011 and reference Alert #19 and we'll send you an 0.1-uF cap at no charge.

NOTE: If you built a KPA100, you have already made the change to C42.