21 May 2012

Locating R1235 on FT-817

Two weeks ago I proposed a "play safe" procedure for testing the health FT-817's ACC port (Vcc line only). If R1235 is blown, what can be done? First let us find out where it is.

Remove all power sources to the FT-817, including the internal battery.
Unscrew the top cover (note, this procedure is the same of the "optional filter installation") and gently unplug the speaker cable: a shiny PCB full of SMD components is exposed. Well, that's not the correct side for R1235.
FT817ND without top cover.
Remove the five screws that hold the board (red circles in the picture above), the flat cable near the DATA connector (yellow rectangle) and the two coax connectors (yellow circles). Now the PCB can be lifted and rotated 180° above the front panel.

Check out the video to understand where you have to look for R1235 on the bottom side of the top board.

And here is an annotated picture of the area of interest:

Area of interest to locate R1235
It is tiny, isn't it?

A Vcc line shorted to ground though this 10 ohm resistor for a couple of seconds increased the resistance to about 7000 ohm. Voltage without load is the same of the supply, but as soon as some current is drawn the voltage reading drops.

Fix? Stay tuned.