Suitable LED Replacement?

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kruser

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Has anyone found a suitable replacement for the LEDs used in the 536HP backlights?

I lost two behind the keypad but the other are still going strong.

They appear to see a max voltage between 2.8 and 2.9 VDC on high but who knows the actual light output.

I also forgot to measure mine and see what SMD size they are but they were tiny.
Still easy for me to replace though.

I know Uniden is planning on fixing this but I won't be without my radio again and would rather replace them myself.

I've not started looking at Mouser and Digikey's offerings yet as I figured I'd ask here first.

I did have some from Mouser but they had more of a bubble lens to make them wide angle so they would not fit under the backlight spreader that Uniden uses to spread the light evenly behind the keys.. The bubble lens hit the light spreader as the LED was too tall. Plus mine were at least one size to large and I would have needed to add a wire to get them hooked up to the existing solder pads. Most likely two wires so they would have remained centered.
That would have made for some work. If I can find the correct size that will handle the voltage (and be as bright), swapping them out would not be hard at all having the needed equipment for working with SMD components.

My display backlights are fine. It's only the four keypad led's that need to be changed. Really only two but I'd probably be unlucky in finding the exact brightness that the OEM lights produce. So I figure I'll purchase plenty to change all but just do the four behind the keypad for now.
 

Voyager

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Considering the trouble Uniden has apparently had finding suitable (durable) replacements, I doubt any common sources would have suitable replacements for the LCD backlight, but the keypad backlight LEDs are more common animals. Unfortunately I don't have any part numbers.
 

XTS3000

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These LEDs are very common. 5 minutes sourcing via Google brought up MANY suitable replacement from quality companies such as KingBright, ROHM, Vishay. All had immediate delivery on the white LEDs in sizes of 201, 402, 603, 804, 1206 in quantities of 200,000 to 1,000,000. These 3 companies produce the highest quality LEDs available on the open market and have zero lead time for delivery.

Seeing as these high quality LEDs are available NOW, Uniden must be sourcing cheap junk LEDs like what's already in the flagship scanners.

Really sounds like more "lip service" and attempts to buy even more time with excuses after excuses.

If you remove a LED on the x36HP, you will realize there is not proper heat sinking on the ground tab of the LED. A simple redesign of the circuit board to include a ground heat sink for each LED would most likely reduce, if not eliminate, the dimming displays even with the cheap LEDs.
 

kruser

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These LEDs are very common. 5 minutes sourcing via Google brought up MANY suitable replacement from quality companies such as KingBright, ROHM, Vishay. All had immediate delivery on the white LEDs in sizes of 201, 402, 603, 804, 1206 in quantities of 200,000 to 1,000,000. These 3 companies produce the highest quality LEDs available on the open market and have zero lead time for delivery.

Seeing as these high quality LEDs are available NOW, Uniden must be sourcing cheap junk LEDs like what's already in the flagship scanners.

Really sounds like more "lip service" and attempts to buy even more time with excuses after excuses.

If you remove a LED on the x36HP, you will realize there is not proper heat sinking on the ground tab of the LED. A simple redesign of the circuit board to include a ground heat sink for each LED would most likely reduce, if not eliminate, the dimming displays even with the cheap LEDs.

Ha, I did not find any heat sinking behind the OEM LEDs!
Mine is an early model and one of the first 200 made.
ALL the LEDs in my 536 for the LCD and the Keypads are identical in all aspects.
Same voltage feeds them all but they are wired in series for each pair of two LEDs. The high side remains at 8 VDC to ground and they float the low side to dim or turn them off.
I did not bother looking at the two that illuminate the function knobs alert ring.

Like you, I also found several suitable replacements at Mouser alone and actually ordered some of the brightest white ones (guessing at the mcd output and color temp) made by OSRAM but I screwed up.
I was in a hurry to make their 8 PM cutoff time for same day shipping and I did not pay attention to the thickness of the models I ended up buying.
They fit length and width wise but not height! The bad thing is I actually had two KingBright models in my cart that would have fit fine but I swapped them for the Osram's as the Osram's had a slightly higher max voltage rating. My 536 measured a max voltage at each LED just under 2.9VDC and the OSRAM LEDs I bought had a rating of 3.2VDC.

I ended up buying two different models made by Osram that were nearly twice as tall as the ones Uniden used so no fit behind the light spreader for the numeric keypad. They may fit for the LCD backlights though as that light spreader appeared to be taller where the LEDs sit.
I still tested the two I bought in free air and current consumption was fine plus they emitted almost zero heat (after burning on high for over an hour) but they had the same or greater light output compared to when my 536 first came out of its box.
A color temp of 5600K was noticeably yellower (still almost undetectable) at the low setting only but would have still been plenty white enough. The other Osram had a color temp of 6500K
They put out 2240 mcd of light if ran at their recommended upper voltage of 3.2VDC, that would have been brighter than Unidens LEDs. My 536 only puts out just under 2.9VDC on high though so I was not running the OSRAM at full brightness but it was still at least as bright or maybe even a tad brighter than when my 536 was new out of the box.

All my LEDs in my early production 536 are identical. Same voltage, brightness, size and color. No difference at all like Voyager found. Maybe they changed something in different production runs.
All my LEDs are also wired in series of two LEDs per series circuit.

With that type of circuit, if an LED failed shorted, it would take out the other instantly when its voltage doubled. If one failed open (or is removed), it would just cause power loss to the other in that circuit.

I also found the reason I'd seen ALL my LEDs go dim for about a week until I opened it up and bumped something before I could find the cause a few months ago.

It was the 35 conductor ribbon cable that connects the front panel board to the main board. I hit it again this time while figuring out the new LED problem and I saw all the LEDs dim slightly or flicker as I bumped around on the ribbon cable.
So I ordered some Molex cables of 50mm length and .050 mm spacing for the contacts. I also stayed with the same connector end thickness of .027.
The only problem was Mouser does not sell a 35 conductor cable. They sell 40 though so I bought that and just trimmed 5 conductors off each end of the new cable.
The new cable was also about 1/2 inch shorter than the one Uniden used. Still plenty long enough with lots of slack so no stress placed on the sockets or the new cable. I did not want to chance using a longer cable not knowing what kinds of signals flow through the cable.
I did try reseating the original cable first but that did not last long at all before they all went dim again. Basically a matter of minutes before they started growing dim.

I must say that replacing that cable only, restored my backlighting to the same level they had when I first turned the thing on!
I don't know if the OEM cable just has cheap tinned ends that compressed or if the sockets use contacts that don't keep their form after time but something sure caused my ribbon cable to no longer make a good connection for at least the 8VDC signal that powers the LED circuits.

Of course if you only have a few LEDs that are dim, the cable is likely not the problem but if ALL LEDs are dim, I'd take a look at the ribbon cable.

The sockets appear to be decent quality and actually have a nice retention mechanism also but who knows the quality of the actual metal contacts inside those sockets.
Swapping the ribbon cable on mine with one of the same thickness as measured at the contact or tinned ends of the original cable sure made a difference in my 536 lighting.

Who knows who made the sockets or the ribbon cable Uniden used but one or the other may be poor quality or I was just unlucky.

I know they have had problems with other models in the past but most of that was caused be heating and cooling causing the ribbon cable to walk themselves out of the sockets. That was not the problem with my 536.

I also lost an LED behind the keypad and that was not caused by a bad ribbon cable so they may have two things going on.

I think most posts on this subject have just some failed LEDs so I may have just been unlucky and got one with a bad cable.
When I first found all LEDs dim though, I knew it was not the LEDs at that time and it had to be something more common to the entire circuit.

If one does not have the skill and proper rework tools, don't even think about attempting an LED replacement. Take up Unidens offer of replacing them if they ever get that program going.

I have the tools and skills needed but I'm not sure my old eyes are up to the task of swapping them all. I'll probably just replace the four behind the numeric keypad and take my chances that the ones behind the LCD will not fail! That poorly connected ribbon cable probably added some life as well plus I do run it on low or medium and rarely on high when I'm actually using it. Otherwise it is used for logging with the backlights off.
With the new ribbon cable, low is plenty bright enough again even with bright room lighting.

Of course replacing my ribbon cable did nothing for the LED that did fail the other day behind the numeric keys. I did not expect it to help either as I knew that one was an LED failure.
 

Voyager

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ALL the LEDs in my 536 for the LCD and the Keypads are identical in all aspects.

That's odd. Some pics posted here on RR showed that the one set of LEDs shine straight outward, and the others shine to the sides. I believe it was the LED backlight that was the latter. They definitely did not look identical.

Of course the fact that one set fails and the other doesn't is another indication that they are not the same. :D
 

kruser

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That's odd. Some pics posted here on RR showed that the one set of LEDs shine straight outward, and the others shine to the sides. I believe it was the LED backlight that was the latter. They definitely did not look identical.

Of course the fact that one set fails and the other doesn't is another indication that they are not the same. :D

On my early production model 536, all the LEDs are surface mounted and aim straight out with the exception of the two that light the alert ring. Those are side mounted above the alert ring and aim down towards it.

I do recall seeing pictures though where some around the LCD were also mounted so they aimed down but mine definitely aim straight out.

I think they changed something along the line. Perhaps after a certain serial number range, a change was made.
I don't recall what my newer model LEDs mounting is. I bought it maybe six months after the 536 came out but the older one with all flush mounted LEDs aiming out was bought darn near the day they released them and has a serial number below 200.

My newer one has never had any LED issues and my older one lost one LED under the numeric keypad but none around the LCD display. They are still burning as bright as they did when it was new. That is thanks to me finding the ribbon cable voltage loss though which caused ALL LEDs to go dim on me.

The Osram models I'd just bought to repair the keypad backlight have a shelf life of one year before they must be mounted. They also came with humidity indicator cards and if they have been exposed to high humidity, they must be baked before mounting.
I think I may have seen this with other high brightness LEDs also and know I've seen such restrictions for other sensitive components.

I also recall someone posting a picture of their front panel with the LEDs powered so you could see the dim ones. I'm pretty sure that was also the pictures where the user had also edited into the picture(s) the actual voltage readings they took across each LED so you could see that difference also.
That's the thread I cannot find again since they redid the Uniden forums again in the past week or two.
I think I also posted in that thread but when I searched on my own posts, I could still not find that thread!
I know I also took pictures of one of my models with the LEDs burning but I did not edit in any voltage readings and I think I may have forgot to attach the pictures. If I did add the pictures, they should be from my early model which would show them all mounted flush and aiming straight out into light spreaders for all but the two for the alert ring.

I'm thinking the picture you saw where some around the LCD were mounted aiming down may have also been the same picture I mentioned above where the user wrote in the actual voltage readings and his radio also had some dimmed or failing LEDs.

My early model has a light spreader for the LEDs above the LCD glass that has one prism like beveled edge of 45 degrees that only redirects the light down and across the LCD from above. The edge of plastic they aim at after turning 45 degrees is also diffused so you don't see a bright spot where each LED is.
The lower row of LEDs also aim into a spreader similar to the upper spreader but the focal point in the lower spreader allows some of the light straight through to light the 5 function buttons below the LCD and it also has the 45 degree beveled edge for each LED that directs some of the light up and across the LCD for even illumination of the LCD.
That bottom edge is also diffused so they do not create bright spots in the LCD from below.

The fact that these things appear to be fairly sensitive to getting them mounted in a year or less and also baking them before mounting if they have been stored above a certain humidity level tells me each LED can change pretty easy if not stored and handled properly.
I don't know if any of that affects the length of life before failure or if it only effects the color temp they produce though. Why would mounting them make a difference if they are placed into a unit that may not even be powered on for over a year! And that unit may also be stored in a higher humidity environment.
My new ones also came with desiccant bags in addition to the humidity indicator cards that told you how to bake them before mounting if they had been exposed to a higher humidity level. What mounting them provides is unknown to me as I can't say I've really studied today's LED offerings but it seems pretty important to the manufacturer that they be mounted within a year and also stored at lower humidity levels up until the time they are mounted.
Maybe they are to be sealed somehow after mounting but nothing said anything about that. That info is probably in the full spec sheet somewhere. I'd only read into the main specs regarding max voltage levels and color temp and overall light output type info.

I think in Uniden's case, they used some of the cheapest LEDs they could source and some fail and some don't. Probably more of a quality control thing on the manufacturer's side than anything. I've seen these handling and storage restrictions before but for components like special humidity sensors or pressure transducers. I don't know that I've ever noticed that for an LED though.
If I did, I probably did not pay any attention as I'd have been using them for short lived or experimental projects.

Someone that works with today's LEDs will hopefully chime in with the reasoning behind the restrictive handling and mounting time limit precautions.

Uniden could have also used LEDs from different manufacturers but with the same exact specs. Some radios could have a mix of different manufacturers LEDs in them.
 

kruser

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Could that ribbon cable have corrosion on the contacts over time from dis-similar metals?

Phil

That is very possible if dissimilar metals are used. I did not try cleaning the tinned ends of the original ribbon cable which is something I'd normally do. That step was missed in this case.
I did look at the cable ends under some decent magnification though and did not see any visible signs of corrosion but could see contact impressions the board mounted sockets created.

I had a Davis weather station console that used a really cheap ribbon cable to connect the LCD to the main RF and Logic board. I'd swear that cable used aluminum foil for the exposed ends! The sockets had basically wore the plated surface of the cable down to the plastic so there was no way it could connect. I remember trimming off one side of the ribbon cable so I could shift it over a few thousandths of an inch where there was still metal.
That actually worked long enough for the new cable to arrive.

The actual sockets in this 536HP could have also had some light corrosion that cleaned up when I put the new cable in. I did not really have the correct lighting to see down inside the sockets very well though especially when mixed with my old eyes and the fine spacing of the contacts in the sockets they use.
 

SCPD

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I also recall someone posting a picture of their front panel with the LEDs powered so you could see the dim ones. I'm pretty sure that was also the pictures where the user had also edited into the picture(s) the actual voltage readings they took across each LED so you could see that difference also.
That's the thread I cannot find again since they redid the Uniden forums again in the past week or two.
I think I also posted in that thread but when I searched on my own posts, I could still not find that thread!

http://forums.radioreference.com/at...434923662-replacing-battery-circuit-crt-5.jpg

http://forums.radioreference.com/at...splay-dimming-issues-bcd536hpdisplayissue.jpg

From these threads:

http://forums.radioreference.com/uniden-tech-support/315481-replacing-battery-circuit-crt.html
http://forums.radioreference.com/uniden-prospective-owners/316423-display-dimming-issues-4.html
 

kruser

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Thanks for the links (again!).
When you replied the other day with one of the links, I read it as RTC and not CRT so I thought you had sent the link pertaining more to the RTC failures by mistake.
I caught it this time and those are exactly what I was looking for!
I now remember the OP of that thread calling the LCD an CRT also.

My front panel in my early 536 is slightly different than the ones pictured with the voltages listed.

I know I took pictures of mine but obviously I forgot to post the pictures as they would have been in that thread.

Mine are all wired in series of two LEDs each.
One of the pictures in that thread shows the 4 above the LCD being wired in series according to the wiring lines the op drew in.
I don't have enough voltage for driving more than two in series.
Maybe that was a mistake and his top four are wired in a series/parallel combo as I've only found a max voltage for the LEDs on mine at 8 VDC and that is only possible if you did not float the ground or low side at all.
Not even enough to drive 3 in series figuring each LED was seeing almost 2.9 VDC on high. And in my early model, they floated the ground side so the max voltage across any pair was only 5.8VDC on high. The high side appeared to be tied directly to an 8 volt regulator.
Perhaps the ops radio has 12 volts at the front panel while my early model only had 8 volt lines.
That would be hard to regulate considering the radio is designed to run at 12 volts or even a bit lower from a car that is not running. Your LEDs would dim with the input voltage if they did wire four in series unless they used lower voltage LEDs. His readings show 3 volts at the LEDs in question though. The regulator would have dropped out when its input voltage approached the output voltage unless they used a voltage doubler in that LED stage. Even LDO regulators require a volt or more above the output voltage.

If whatever they are using to float the ground goes shorted, that could in theory provide 4 VDC across each LED until one or both burned open.

I played with some of the Osram LEDs I just bought. I brought the voltage up just a 10th of a volt or so above their 3.2 max rating and they turned dim almost instantly and never did regain full brightness when lowering the supply back to 3 VDC or so. They remained burning at their new low level though. Just like the dim ones people are seeing in their x36HPs.
Raising the supply to around 3.5 VDC did them in and no light output at all.
All in a fraction of a second also for either test.
My next test will be to run an Osram right at its max voltage and see if they last minutes, hours or days and also see if they start producing heat which they did not do at 2.9 volts.



 

SCPD

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Thanks for the links (again!).
When you replied the other day with one of the links, I read it as RTC and not CRT so I thought you had sent the link pertaining more to the RTC failures by mistake.
I caught it this time and those are exactly what I was looking for!
I now remember the OP of that thread calling the LCD an CRT also.

My front panel in my early 536 is slightly different than the ones pictured with the voltages listed.

I know I took pictures of mine but obviously I forgot to post the pictures as they would have been in that thread.
.

No problem, thought I would throw the link out again since threads sometimes get buried quickly. Been following your and the other technical posts about this for a while. My 536 is at the 13 month mark with no sign of dimming but it is good to know there are options.

You did post 3 images of your findings back in late April to a separate thread:

http://forums.radioreference.com/un...-fading-50-loss-brightness-5.html#post2382253
 

kruser

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No problem, thought I would throw the link out again since threads sometimes get buried quickly. Been following your and the other technical posts about this for a while. My 536 is at the 13 month mark with no sign of dimming but it is good to know there are options.

You did post 3 images of your findings back in late April to a separate thread:

http://forums.radioreference.com/un...-fading-50-loss-brightness-5.html#post2382253

I need your search skills! Thanks for finding that as I knew I'd posted more info on this.

I stand corrected though. Yesterday I said there were 5 above and below the LCD. It's actually 4 across the top and 6 across the bottom

Mine are all still wired in series with two LEDs per group.

I've still not bothered looking for the drivers on the rear of the board but I think each driver chip may run at least two series circuits so there should be 7 drivers that are responsible for dimming all 14 LEDs.
I don't know if the voltage drop from true ground is done in the driver or with a common or several external resistors that float the ground so each series circuit can only produce 6 VDC (5.9 in mine).
The high (positive) side is common for all 7 series circuits and measures 8 volts to ground and does not change at all when you dim or turn the LEDs off. The low side is floated at least 2 volts away from true ground which gives the circuits the 5.9VDC max voltage.
I did not find any issues with the driver circuits though. They all supplied the correct voltage across each pair of LEDs.

Being as they are wired in series of 2 LEDs each, a slight difference in current draw of just one LED would cause higher voltage on the other in that circuit. I wonder if that is why only some are failing and the failed ones being the ones that saw the higher voltage.
If Uniden chose an LED with a max voltage of 3.0 VDC, that is pushing it as some have measured higher than 3.0 across some of their LEDs.
I did not find any above 2.9 in mine. Mine all measured less than a 10th of a volt difference and most were within .02 volts difference of each other.

After I had the problem recently and lost a numeric keypad LED, my voltage across that pair returned to normal when I temp wired in one of the OSRAM LEDs I just bought. I was actually surprised at how even the voltage was across both LEDs in that circuit.
I must have been lucky and the Osram models I bought had an exact current draw as those Uniden used otherwise I'd have seen an imbalance in voltage across each LED in that pair. Mine came out no more than 0.01 volts difference between the Osram and Uniden's LED.

I still think the LEDs are just very cheap quality and the max voltage rating claimed may not be consistent from one LED to the next or there is a difference in current draw between the LEDs in a pair that causes one LED to see a higher than max voltage across it.
The high one will be the one that is damaged and goes dim or dark but usually still passes current and keeps the other in the pair burning.
Both would need to be replaced in that pair.
 
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