Yaesu FC-107 Meter lamp repair
This may be similar to the IC-751A meter requested by another user.
I was most disdained to find out one of the lamps in my expensive new Yaesu FC-107 Tuner was burnt out. These lamps run on 8V supplied by the FT-107M.
I took off the cabinet to see what was involved in repairing the burnt out lamp. They didn't make it easy.
the lamp is INSIDE the meter, down below the display. I unsoldered the 8 sets of wires to the meters, and removed the PCB mounted above it. Now I can take out the meters as a unit. one screw holds the meter bracket in place.
Both meters are attached to a metal plate by doublesided tape, and you don't want to mess with that. That insures perfect alignment when reinstalling the meters.
Take off the metallic tape around the outside edge of the meter and save it. It is very important to keep. There is also some black plastic tape on the bottom edge for some reason. Save that as well. Finally there is a Scotch clear tape going around the front of the meter which holds the meter front case to the meter. Removing that will allow the case to be tilted up and provide access to the lamp.
The lamp is a VERY OBSCURE and IMPOSSIBLE to find bulb. It has metal leads coming out of each side of the bulb. VERY unusual!! No chance you are going to find this bulb. What to do?
I examined the layout and circuit and decided a 6V bulb would work. But a series resistor is needed to drop the extra 2V the power supplies supplies. Put 8V on the bulb and it will burn very bright for a short time.
The bulbs chosen are the Radio Shack colored lamps that come in a pack of 3. Must be Christmas lights. They are the correct size, but have 2 leads coming out the bottom. Also, it is necessary to remove the colored coating. RS P/N 272-1098, Cheap too!
I had some Acetone which took off the coloration very nicely and turned them into Clear bulbs. When you pulled out the burnt out bulb, it has a blue colored plastic sleeve over it. remove this sleeve carefully and slide it over the new bulb. Mount the bulb in the center of the meter with the leads coming out to the left. One lead is cut to about an inch and soldered to the connection post. The other lead is cut to about 2 inches.
Now, score a 33 ohm, 1/4W carbon resistor and bend the leads in an S fashion so they route back over the resistor body. Cut them to about 1/4 inch length over the resistor body. Solder one side to the other Connection post. The remaining wire solders to the other resistor wire.
After carefully positioning the lamp inside the meter to be exactly centered, the case is folded back down and locked into place with the same piece of scotch tape. The metallic tape is wrapped around the outside and finally the black tape placed back over the bottom. Now you can re-install the meters in the FC-107 case and connect back up the wires.
Powering it up, the new lamp has the EXACT same intensity and coloration of the old meter bulb. GREAT!!!! I took the 2 remaining bulbs and taped them inside the case so next time a bulb burns out, there will be the lamps to use.
Wonderful repair only took a short time and will last a lifetime (or until a bulb burns out again)
Last edited by WA6MHZ; 01-22-2012 at 08:26 PM.
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