Yaesu Ft-736R Meter Light replacement
I have one light bulb that is burned out for the meter in my 736R, and I would like to know what is involved in replacing them, and what bulb's should I get for it? Thanks
Work Smarter not Harder.
I would disassemble down to the dead bulb, remove it and look for suitable replacement.
Many of the smaller lamps today may not have markings. The way around that is to power the unit up and use your Voltmeter to find out what is driving the lamp, and whether it is AC or DC. From there, you can usually pick out the proper lamp from mfr's sites or catalogs.
For example, typical voltages for these lamps may be 6V, 8V, 12V.
Lamp package type may be "fuse lamp" in which the lamp looks much like an AGC type fuse and is held in a "fuseholder" type of socket, or may be leaded and soldered in.
Or it might be what we used to term the, "grain of wheat" bulb, a small all-glass lamp with wire leads, or perhaps a "bipin" type.
Once you have the lamp and the voltage measurements in hand, should be a rather simple job of persusing parts catalogs to find the right lamp. Mouser, Digikey, mcmelectronics, etc.
Thank you for the information. I will open it up and check it out. 73
Work Smarter not Harder.
Ft-736 meter requires two grain of wheat style 12 volt lamps, with flying leads. RadioShack probably has them. I believe they are 50mA type.
The lamps have a silicone blue-tinted jacket over them. They mount on two clear plastic ears that are part of the meter assembly. If you drop the front panel forward, you can replace the lamps quite easily. One problem, the plastic can become very brittle due to the heat produced by the small lamps, and if you break off an ear it will be very difficult to illuminate the meter properly. My 736 lost both ears, and I had to jury a system of bright LEDs for meter illumination.
My light burned out to
The Radio Shack one I had was to big to fit in the holder its a 5mm but I found one that did fit but I dont know were I got it its I think a 4.7m it is smaller when you put it up to the Radio Shack one a tad and it fit right in the holder just right, but what size of LED did you use when you put in leds thats what I want to do is put the super bright white LED but I need to know what size led to get the 5mm iam looking at is 3.2-3.4 foward voltage and what size resistors should I get for the led? I have some 3mm but they are to small. Can I get a little help on this please
Voltage dropping resistor
Pete, K1ZJH, reported that the original “grain of wheat” lamps are 12V. I can’t help you with the physical diameter of those lamps—perhaps N8DXB can measure the diameter with a caliper when he opens up his unit.
The resistor value you need should be about 440 ohms (Choose the closest commercially available size.) That value is calculated using Ohm’s law by subtracting 3.2V from 12V (to get the required resistor voltage drop) and dividing by 20mA, the nominal forward operating current for most of the smaller LEDs. Check the package for the particular LED you choose and modify this resistor value according to it’s typical operating current. Note your LED’s “maximum” forward current (often about 30mA) and choose a resistor large enough so as not to exceed that value.
The I-squared-R loss in that resistor is about 180mW, so a half-watt resistor would be plenty large enough. If you’re really cramped for space, though, a quarter-watt resistor should still give you enough margin.
The following thread provides a recent example of an LED replacement for “grain of wheat” incandescent bulbs:
Last edited by NG6R; 02-09-2011 at 05:38 PM.
Unfortunately, LEDs don't work on the FT-736R. I converted mine only because both ears were damaged by the heat from the lamps, and had become brittle and snapped off. This involved removing the meter, filing the remains of the tabs flat, and installing the LEDs so they projected into the rectangular surfaces that were filed smooth. Simply inserting the LEDs in the plastic ears will not work, since the illumination is in the wrong direction. I used super bright LEDs, and the results were marginally acceptable; it wouldn't be my first choice.
The suggestion for using the RS lamps was given on a Yahoo! forum for FT736R owners: http://groups.yahoo.com/group/FT-736R/message/146
As I mentioned, my meter was damaged and I couldn't go back to incadescent miniature lamps in my unit.
Last edited by K1ZJH; 02-09-2011 at 06:58 PM.
LED light diffusion
Pete has a very good point. Many of the “bright” LEDs are so named because they are constructed with a convex lens to throw their light in a relatively narrow beam. So, if you are looking at it “head-on,” the light is quite bright. If that beam is not in the correct direction in your application, however, the emitted light is not very useful. One technique I’ve used to achieve a diffuse light of sufficient luminosity is to scuff the LED’s surface with fine sandpaper. The following photo shows two “bright blue” LEDs in series.
One LED clear one scuffed.JPG
The one on the left comes directly out of the package and shows about a 12 degree wide light pattern. The one on the right has been scuffed all around with fine sandpaper and gives off a more diffuse light pattern. If you are really set on using LEDs instead of incandescent bulbs (especially if you want to experiment with some non-white color displays), this technique might provide the light level you need.
73, Jerry, NG6R