Fl-2100B Amplifier

Bias Modification

For Svetlana and Taylor 572B tubes

Technical Bulletin

Yaesu U.S.A. — Amateur Products Division — Technical Support

File No.: TB-9627 Date: July 16, 1996
Model: FL-2100/B Serial No. Range Complaint unit

Problem: Oscillation causes burned components when using Svetlana  & Taylor 572B tubes.

Expected Results of Modification: Improve Circuit.

Component Value Changes: Main Unit
Part Location No. From To New Part No.

Added/Deleted Component: Main Unit
Part Location No. Device Type Added/Deleted New Part No.
  10D10 A G2090002
  1000uF     25WV A K40149005
  22 ohm     1W A J20306220

See Diagrams

Bias Level Adjustment   After the modification is completed, you must adjust the bias level. With the function switch in the operate position, activate the amp relay with no RF drive applied. Adjust R4 for an idling current of 0.03 amps on the IP meter.
DO NOT adjust to 0.090 as in manual.