Replace Your Rig`s LCD Panel Lamps with SMD
Contents
1. 9v is available inside the display assembly As each led has a forward voltage drop near to 3 0 volts 3 in series will need greater than 9 volts to operate properly The other alternative would be to connect the 3 led s in parallel and operate them from the 9v inside the display assembly with a suitable series current limiting resistor The advantage of this approach is that no external connection would be needed for13 8 volts However the big disadvantage would be the extra wiring needed to interconnect the 3 led s in parallel This would be quite difficult to do given the very limited area for routing twice aS many wires If you look at photo 5 think you can see what mean realize of course that the situation may be quite different with other radios Finally after making this decision needed to find a solder point on the main pcb that was close to 13 8 volts and also that was switched off when the radio power button was operated Unfortunately the service manual schematic and pcb layouts had didn t seem to fully agree with the actual radio layout ended up using my digital multimeter to locate a suitable power point which was only 0 5 volt lower than the incoming 13 8 volts Preparing the LED s for mounting In order to prep the led s for mounting refer to Photo 4 Don Dorward VAS3DDN Page 3 11 9 2014 Reprinted with the permission of The Canadian Amateur Copyright VASDDN Nov Dec 2014 TCA p18 A2. Dec 2014 TCA p18 Photo 7 shows the wire routed up the rear panel near the radio 13 8 v DC power leads and into the area beneath the radio top cover The corner of the rubber strain relief used for the radio 13 8 v DC power leads has been shaved off with a sharp knife to permit the red led power wire to enter ithrough the chassis The black heatshrink covers the 4 watt CF 330 ohm resistor which sets the forward current and hence the brightness of the 3 led string used 330 ohms to set the led current to approximately 14 mA You may want to experiment with this value for the most pleasing appearance and brightness Don Dorward VAS3DDN Page 6 11 9 2014
3. It was also evident that a diffused led would better simulate the tiny incandescent lamps Led s are usually available with either a diffused or clear lens Ref discussion at https www jameco com Jameco workshop Tech Tip light brightness intensity html also had located some smaller 3mm T1 amber LED s that were rated at only 10 mcd and which proved not nearly bright enough in my crude test although the color seemed perfect Most importantly still had not figured out how to mount these radial leaded parts in the original lamp positions but fully on top of the Icd display pcb It was beginning to look like this project was going nowhere as an extensive catalogue and on line search turned up no 700 mcd 3 mm leaded amber LED s It finally occurred to me that there were lots of white high brightness SMD LED s around and all one would need to do would be to put a small piece of amber color tape or film over it to act as a color filter and simulate the sem amber glow from the tiny lamps 7 Once again rooting in the junk box gt turned up a part reel of high IT brightness strip LED s the kind a that already have a current limiting OU II resistor in series with 3 SMD LED s Narn White 200k 5M 3528 Waterproot SM and operate from a nominal 12v DC The led s come mounted on an adhesive backed copper strip and covered with a soft protective clear silicone coating to make them waterproof They were intended to
4. be cut off as required in multiples of 2 The ones had were described as warm white Photo 3 and visualized mounting them to the radio pcb by using a small rectangle of double sided mounting tape Although these led s did not have a diffused lens they are described as having a wide viewing angle of 120 degrees p iit Vile i I Varnm V Don Dorward VA3DDN Page 2 11 9 2014 Reprinted with the permission of The Canadian Amateur Copyright VA3DDN Nov Dec 2014 TCA p18 Since the tiny lamps being replaced were mounted horizontally they would have had a limited viewing angle of 180 degrees Therefore hoped that this Small viewing angle trade off would work Alternative sources of suitable SMD LED s No don t really expect everyone who reads this to have the same LED s available to them The LED package size used is called a PLCC2 or 1210 which is close It is commonly used and am sure one can locate suitable parts from distributors like Jameco Digikey etc Or even from eBay with SMD led PLCC2 3528 in the search bar For example J ameco lists their p n 334756 However the difficulty of using loose un mounted led pieces will be in the handling soldering wires to them and mounting to some secure Surface which will not short to the radio pcb How to connect the LED s The FT 6200 front panel and display assembly is removable for remote mounting Perhaps because of this only a regulated
5. Reprinted with the permission of The Canadian Amateur Copyright VA3DDN Nov Dec 2014 TCA p18 Replace your rig s LCD panel lamps with Surface Mount LED s By VA3DDN Don Dorward There have been a number of articles in the recent past that describe replacement of incandescent panel lamps in radios with Light Emitting Diodes LED s Photo 1 shows the front panel of my treasured old Yaesu FT 6200 mobile ET vasu eT en transceiver with 2 of the 3 original fe no ay ESE panel lamps used to back light the z 4am LCD display burnt out The service manual optimistically says to unsolder the old bulbs and install replacements Easier said than done as found out due to the closely packed Surface Mount Devices SMD on the control head pcb and the very Small copper soldering lands on the pcb used for the mini lamps originally used 9 volt Yaesu p n Q10000065 To be brutally honest actually did try to replace the tiny lamps but confess botched the job and ended up damaging the pcb and being unable to clear the holes of solder highly embarrassing for me as have spent over 40 years in the electronics industry and used to judge solder joint quality according to IPC standards Anyway lived with it this way for quite a long time but finally decided to fix it permanently Photo 2 shows the new improved backlit illumination on the FT 6200 using surface mount led s instead of the tiny lamps S
6. o here is what did As described concluded that my only remaining option was to find and use some small amber colored led s that could possibly be hot glued in place on top of the display pcb and power them with a small wire harness running to the outside of the radio control head Not at all elegant but perfectly practical However quickly found out that the standard size T1 3 4 LED about 5mm dia was just too large to fit in the small places originally occupied by the mini lamps Too bad because had some in the junk box rated at 700 mcd These had a clear lens which abraded with sand paper to simulate a diffused appearance With the radio front bezel removed dangled one of these led s near to the side of the LCD display as a trial and was very pleased at the Don Dorward VAS3DDN Page 1 11 9 2014 Reprinted with the permission of The Canadian Amateur Copyright VASDDN Nov Dec 2014 TCA p18 appearance Even though could not use these led s due to size this simple test told me that did need to use high brightness led s for the application Side Bar LED specs The brilliance or light output of LED s is commonly given by the manufacturer as the number of milli candelas mcd at a fixed forward current usually 20 milli amperes mA One rule of thumb suggests that standard brightness LED s have light outputs less than 100 mcd whereas high brightness LED s typically out put gt 700 or more mcd
7. t the top of the photo is the cut off piece of the led strip about 2 long showing 3 led s and the single series current limiting resistor The 2 row shows the 3 led s snipped out of the strip we will not use the Small resistor The 3 row shows the led s now stuck to a small piece of 3M 414C double _ sided mounting tape Note that the clear silicone coating peeled off of the each led use tweezers or small needle nose pliers to gently peel the coating off At the bottom is one of the led s prepared as above but shown with connecting leads to the anode red and cathode black This particular Style of smd led is called a PLCC2 smd package The cathode end is marked by the diagonally cut bottom left corner of the led Note when soldering the leads to the led first strip and tin the wire end Then hold the tinned wire end to the exposed solder at the top and then the bottom of the led package while using your smallest pointed soldering iron tip also freshly tinned to quickly reflow the solder Excessive heat will damage the led Positioning and connecting the LED s 7 a y j a ora ar Ma a 1 NS i d 2 gt j f N a A amp a DS ee S J Am ee a a m oo Se se amansi TA j Referring to Photo 5 the radio front panel bezel has been removed and if you look closely you can see the left led1 and center led2 led s the yellow dots moun
8. ted in place Each led has had a small amber colored piece of tape stuck on to it This was cut from a left over bit of 3m 5413 polyimide electrical tape Note you could also use a piece of amber lens Don Dorward VA3DDN Page 4 11 9 2014 Reprinted with the permission of The Canadian Amateur Copyright VASDDN Nov Dec 2014 TCA p18 repair tape from the local auto parts store or even better a small piece punched out of an amber color binder tab The led s are connected in series as shown in Fig 1 The cathode end of led1 is connected to the ground tab on the tuning control mount with a short piece of black 28 30 stranded insulated wire FIGURE 1 SEE TEXT FOR LEDS to radio 12w switched 12V RIGH LEFT CENTER 330 ohm 1 4w R1 Radio chassis ground Ledl was originally prepared with 3 lengths of wire After peeling off the double sided tape paper the led assembly was pushed into place with tweezers Then the connecting wires were carefully routed clipped to length and tinned The same procedure was followed with led2 and led3 with the last red wire about 8 from led3 anode routed straight out as shown to the side of the 8 pin mic connector Photo 6 shows the red led power wire exiting the front panel bezel through a 3 32 clearance hole and taped to the radio bottom cover Don Dorward VAS3DDN Page 5 11 9 2014 Reprinted with the permission of The Canadian Amateur Copyright VA3DDN Nov
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