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Author Topic: Wouxun KGUV6D V2 HT Flashlight LED Voltage?  (Read 14947 times)
KT0DD
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« on: May 20, 2013, 03:02:23 PM »

Hello, does anyone know what the voltage rating is for the white built in flashlight LED on the Wouxun KGUV6D V2 commercial HT radio?

 I have had several failures of the built in flashlight LED in a couple of my KGUV6D Wouxuns. I just had another LED failure again only a week after having one repaired. My dealer has been great at honoring the warranty repairs, however I am wondering if he is using substandard Chinese LED's supplied by Wouxun and I want to buy my own from a local Motorola shop and send it along with my radio this time to see if it solves this problem. I'm also asking him to check any in line voltage dropping resistors as well.

I find the flashlight option quite handy in my work and for a $150 radio, it should work properly.

Any info is appreciated.

73, Todd - KT0DD

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N4NYY
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« Reply #1 on: May 20, 2013, 03:23:34 PM »

It might not have been designed to be use in the manner you are using it. My suggestion is get it fixed one last time, and stop using it for a flashlight for work. Use it sparingly.
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KE3WD
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« Reply #2 on: May 20, 2013, 05:01:11 PM »

If you going to buy your own LED, the volt drop for the one the mfr used isn't an important issue at all. 

Take a look at the connect points for the original LED, find the dropping resistor, which should be close by and connected to the positive lead via a trace. 

Measure the resistance of that dropping resistor. 

Might also be a good idea to power on and measure the voltage from top end of that resistor to chassis ground. 

Ohm's law and the specsheet for the new LED can be used to calculate the proper dropping resistor to install - or it might end up to be the same as the one already in there.  If you don't know how to calculate the value, Bing search can bring up endless howto webpages on that subject.

73
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KT0DD
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« Reply #3 on: May 20, 2013, 06:01:05 PM »

LED's are supposed to last several thousands of hours installed in a properly designed circuit. That's why they replaced the old wheat lamps on most all modern radio displays and why they are being touted for replacing incandescent bulbs in the home. They are energy efficient and long lasting. Besides, I do not use it much at work anyway but it's handy when I DO use it.

I appreciate KE3WD's idea, however, the radio is under warranty and I do not want to open the case and void the warranty, therefore I cannot perform tests. I was trying to furnish something of better quality to the tech that would be an easy drop in replacement so he wouldn't have to do much fiddling around.

« Last Edit: May 20, 2013, 06:03:13 PM by KT0DD » Logged
N4NYY
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« Reply #4 on: May 20, 2013, 06:06:46 PM »

LED's are supposed to last several thousands of hours installed in a properly designed circuit. That's why they replaced the old wheat lamps on most all modern radio displays and why they are being touted for replacing incandescent bulbs in the home. They are energy efficient and long lasting. Besides, I do not use it much at work anyway but it's handy when I DO use it.

I appreciate KE3WD's idea, however, the radio is under warranty and I do not want to open the case and void the warranty. I was trying to furnish something of better quality to the tech that would be an easy drop in replacement.



The LEDs that are supposed to last thousands of hours are more of the common LEDs. If this is a high power LED, I am not sure they have the longest endurance. Now, saying that, this is a Chinese radio, and they use Chinese parts. FWIW, I have ordered those bulk LEDs from Hong Kong, and I can tell you from first hand experience, they do not last as long as they are supposed to. I have seen them go out, and dim over time, even with an more than adequate drop resistor. 
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KT0DD
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« Reply #5 on: May 20, 2013, 06:30:45 PM »

Thus, the reason for my wanting to find a better quality part. I know the Chinese parts can be inferior quality, but sometimes not. Many people (not you) like to bash the newer Chinese radios flooding the market, however several of the models offered by the "Big 3" ( i.e. Yaesu FT-270) and even Motorola are made in China now. Anyway, I have a friend who's had his Wouxun for a couple of years now and he's told me he's dropped it hard several times and his flashlight option still works. One of my KGUV6D's I've had the LED repaired on still works fine 2 months later with moderate use. So I know it can work.
« Last Edit: May 20, 2013, 06:36:13 PM by KT0DD » Logged
N4NYY
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« Reply #6 on: May 20, 2013, 06:42:47 PM »

How strong is the LED? The 1W or more LEDs, suck up battery power.
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KT0DD
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« Reply #7 on: May 20, 2013, 07:34:16 PM »

That's the problem. I don't know any of the ratings as the owners manual has no schematic for me to look at and I am not aware of any schematics or service manuals available for this radio. This is  one drawback of the Chinese rigs. Tech info is unobtanium.

I don't turn the flashlight on and just leave it on. I use it in 15-30 second bursts at the most for only 8-10 times a day, so battery consumption is not a concern.
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KA4POL
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« Reply #8 on: May 20, 2013, 09:51:55 PM »

The critical value for LEDs is the current. The ones in Wouxon or Baofeng have a limit of 20 mA as regular current. If yours gets bad I'd say a higher value resistance in series should do the trick. Why don't you ask you dealer about that? He could check and increase the value of the existing series resistor.
From the KGUVD1 I know that the LED is switched via a transistor and a 150 Ohm R. May be 180 Ohm works better.
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KX8N
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« Reply #9 on: May 21, 2013, 05:18:47 AM »

That's the problem. I don't know any of the ratings as the owners manual has no schematic for me to look at and I am not aware of any schematics or service manuals available for this radio. This is  one drawback of the Chinese rigs. Tech info is unobtanium.
You just have to look harder. Here's a link to the service manual. Just searched for it on Google.

http://wouxun.su/UserFiles/File/service_manual_wouxun_kg_uv6d.pdf
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KG4RUL
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« Reply #10 on: May 21, 2013, 05:29:15 AM »

Comparing the brightness of the "flashlight" LED on my UV6X, to one in an actual flashlight, I get the impression that they are running the UV6X LED way beyond it's ratings, to get that level of light from it.
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K5LXP
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« Reply #11 on: May 21, 2013, 06:55:48 AM »

The critical value for LEDs is the current. ... check and increase the value of the existing series resistor.

Correct.  I also note from the schematic that the power source of for the LED's is direct from the battery.  LED's being nonlinear devices can see a huge swing in current for a small change in input voltage.  The battery can exhibit probably a volt or more difference from full charge to dead.  The series resistor would have to be chosen for the highest expected voltage.

Another enemy of LED life is heat.  Even if you run an LED within current spec, if you can't adequately heat sink the die it will burn out.  You'd have to verify if the PCB and radio case allow for adequate thermal conduction and dissipation.

I'm going to bet that not a lot of reliability engineering went into this "feature".  It was anticipated one might use this for a few seconds to find your keys or whatever, not serve as general illumination.  A similar situation exists for smartphones.  You can get apps that turn the camera flash LED on continuously, turning your phone into a $500 flashlight.  I wonder how many people have burned out the flash LED's in their phones doing that. 

LED lights are ubiquitous anymore so if a continuous duty light is what you're after, just buy a dedicated light for that.  If the LED light in the radio is of prime importance, crunch the power and thermal numbers for what the radio can accommodate and pick an SMD LED that will best fit.  That would be a big project for something that could be solved as simply as buying a $3 AAA flashlight at Harbor Freight.


I get the impression that they are running the UV6X LED way beyond it's ratings, to get that level of light from it.

You'd be surprised.  I've done a bit of work prototyping LED light assemblies for a national lighting company.  I've built some arrays using 5x5mm LED's that are so bright you don't want to accidentally look at them - they're like looking at the sun.  Put 144 of them on a 5" disc and you've got something as bright as a streetlight - which is exactly what they have in mind.  You still need to get the heat out though no matter how efficient they may be.  It's especially challenging when you have these tiny packages that you need to get several watts of heat out of, then multiply that for an array.  I would bet that the LED in the HT may be nominally within the current rating but they didn't accommodate the thermal dissipation for worst case.


Mark K5LXP
Albuquerque, NM
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KE3WD
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« Reply #12 on: May 21, 2013, 08:05:24 AM »

LED's are supposed to last several thousands of hours installed in a properly designed circuit. That's why they replaced the old wheat lamps on most all modern radio displays and why they are being touted for replacing incandescent bulbs in the home. They are energy efficient and long lasting. Besides, I do not use it much at work anyway but it's handy when I DO use it.

I appreciate KE3WD's idea, however, the radio is under warranty and I do not want to open the case and void the warranty, therefore I cannot perform tests. I was trying to furnish something of better quality to the tech that would be an easy drop in replacement so he wouldn't have to do much fiddling around.




Sending the tech your own selected LED would also very likely be a warranty-voiding situation if the tech were to install same. 

And assuming that the problem lies in the LED itself does not take into account another possibility -- it very well could be that there is the wrong value dropping resistor in the radio, which would be the real reason the factory LED's are being destroyed. 

Why not just return the radio for repair and indicate, in writing with the rig, your request to check out and change that dropping resistor as well?  A reasonable request considering the repeat callback on the repair. 


73
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N4ATS
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« Reply #13 on: May 21, 2013, 02:21:57 PM »

I studied the schematics , they are pretty much throw-away  as every single curve was taken to get the cost down and you can replace the entire HT for under $40.00

They are a generic China made , kinda like "IIcom" (Not Icom) and "Kenwoo" (NOT Kenwood)

Here is the Baofeng version which comes with a crap load of extra stuff... Also they have several other names like boopang WX , Mo-py FM and a host of other non-listed names

http://www.slickguns.com/product/new-baofeng-uv-5ra-ham-two-way-radio-free-shipping-4217
« Last Edit: May 21, 2013, 02:27:08 PM by N4ATS » Logged
KE3WD
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« Reply #14 on: May 21, 2013, 02:32:44 PM »

boopang

gotta luvit

what, no yatsoo? 

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