Yaesu FT-227-R CTCSS Tone Board

The heart of this tone board is the 567 Tone encoder/decoder. The common designation is NE567 made by Signetics, I had a number of XR567's laying around but don't look for one of those, Exar went out of business long ago. The one drawback to using this IC is that frequency adjustment is tedious and difficult to do on the fly, especially if the board is mounted inside. The three repeaters I want to reach all use the same tone so I'll set it there and forget about accessing any others for the time being.

Here are the original designations for the tone squelch board used by Yaesu:

Preparing the FT-227

Rewire ToneSQ switch

In order to use the Tone SQ switch on the front panel to activate the CTCSS tone I rewired the switch so that the front panel squelch control stays activated even when the switch is depressed. To accomplish this perform the following:

  1. remove top cover
  2. remove the red wire from the post to the left of VR103 (immediately to the rear of the tone board mounting area) and insulate the end of the wire with heatshrink.
  3. remove 3 screws securing PLL/BOC board and lift to expose switches
  4. locate Tone SQ switch (3rd from left) there are 6 terminals
  5. solder one end of a short wire to the rear right terminal
  6. solder the other end of the wire to the front right terminal
  7. replace BOC board

Prepare mounting area

For constructing the tone board I used half of a Radio Shack (276-148A) Dual General-Purpose PC board. In order to make it fit in the space intended for the original tone squelch board, perform the following:

  1. remove bottom cover and disconnect speaker wires
  2. remove rear-most screws on side securing PLL board
  3. Hinge PLL board forward exposing trace side of Main board
  4. remove green wire that connects post (E) and R160
  5. remove post (E)
  6. remove yellow wire that connects post (C) and R135
  7. unsolder red sheilded wire at post (I) and resolder to post (C)
  8. unsolder the other end of the red sheilded wire from R217 and resolder to anode of D202
  9. remove post (I)
Pin (C) then fits through the hole in the upper left corner of the project board and now becomes the "Tone Out" connection. (Note: the photo above does not show the 47k resistor and .01 cap at the output.)

Build the circuit board

This circuit converts the square wave output from the 567 to an acceptible sine wave.

The level adjusts from 0 to 2 volts peak to peak. I adjusted the 100k pot to just under a quarter turn and it was enough to break the squelch of the repeater. Use a frequency counter to set the tone.