Replacing the battery circuit CRT

[Voyager]

Unfortunately, these days, my guess is that manufacturers would likely consider this material "proprietary"

Actually, it was a discussion between the FCC and the scanner industry that led to the schematics being withheld. The FCC was concerned about reverse engineering that could restore the cell band.

 

[ratboy]

I've had some stuff with those tiny LEDS that run hot enough that I've wondered how they stay working. I have a little lantern that can be used as a hand warmer after it's on for 15 minutes due to the LEDS generating a ton of heat. Uniden driving them too hard would explain a lot. Is there any part of these radios where Uniden actually did it right with regards to longevity? The USB port seems to be very fragile, as does the micro SD card "cage". I guess they figure they are in the driver's seat for future scanners and don't care if they last or not. One more reason to hope Whistler makes it. I have to admit, I've never understood Uniden as a company, going back to the days where they had the "200/205" (and other) models where they were made in another factory and slightly different in color, but otherwise identical, and sold through different channels. I usually looked for the "05" models because they were cheaper. Having opened up a lot of them, I saw no real difference between them.

 

[garys]

There are threads on this going back probably to the Usenet days, it's pretty well known. Of course now that this policy has been in place for 30 years, it could literally take an act of Congress to reverse it.

Actually, it was a discussion between the FCC and the scanner industry that led to the schematics being withheld. The FCC was concerned about reverse engineering that could restore the cell band.

 

[Boatanchor]

I disarmed again the radio to take voltage readings , it is a good question of the fact that all the LEDs seem to have the same intensity of brightness. I have noticed that there are LEDs in series I've marked in the picture, I've also taken the voltage value in some leds with different intensities dimmer. Take note that the maximum intensity voltage exceeds 3V, in the LED display , that might explain why these are damaged faster.

Voices are heard

Thanks for taking the time to measure the LED drive voltages henrygb.

It does appear that the four LCD illumination Leds are driven a fair bit harder on the high setting in particular, than the keypad Led's. Interesting that on the Low and mid setting, there is very little difference in applied voltage between the two groups.

There is such a large variation in VF ratings between different manufacturers and even different color/brightness BINS within the same model from the same manufacturer in 0603 style LED's that it would be very difficult to get this right when you are trying to squeeze maximum luminus flux out of such a tiny LED.

These things are obviously being overdriven. The fix will either be to replace the LED's with another model with a slightly higher VF (possibly at the cost of slightly lower output/brightness), or modify the power supply circuit to reduce the voltage applied to these four Led's, which again will reduce the brightness slightly.

Regardless, it would be nice if Uniden could source a white led with a color temporature closer to 6000K instead of that god aweful 7000K+ blue/white that they seem to love so much.

 

[mancow]

Have we ruled out pulse width modulation?

 

[Boatanchor]

Not yet

 

[henrygb]

The fix will either be to replace the LED's with another model with a slightly higher VF (possibly at the cost of slightly lower output/brightness), or modify the power supply circuit to reduce the voltage applied to these four Led's, which again will reduce the brightness slightly.

Or just avoid using the brightness at maximum intensity.

I use the radius to a minimum intensity, and so far I have not noticed a decrease in the brightness . The day I note , I'll disarm the radius I'll read voltages and thus a definitive conclusion of which will cause for the failure, course will I change the LEDs .

For now apparently Uniden just changes the LEDs to fix it.

On second thought, this may be the solution via firmware by Uniden, prevent the user from using the maximum intensity of brightness

 

[Voyager]

On second thought, this may be the solution via firmware by Uniden, prevent the user from using the maximum intensity of brightness

If the issue is over-driving the LEDs, the firmware could fix it (by lowering the voltage on the high setting). Of course, that would not 'bring back' any LEDs that are 'damaged'.

 

[garys]

For now apparently Uniden just changes the LEDs to fix it.

On second thought, this may be the solution via firmware by Uniden, prevent the user from using the maximum intensity of brightness

We know that Uniden replaces the diodes. We know that Uniden identifies them on the schematic as D415-D418. What we don't know is if Uniden has issued a ECO with a different diode. I don't think there's anyway we will know that unless Uniden tells us.

So far, it appears that Uniden is replacing the diodes at no charge to the owner other than one way shipping.

If I send my second 536HP back, I'll use a slower and less expensive shipping method, but that's a different story.

 

[scanboyca]

Root cause needs to be addressed

Thanks for taking the time to measure the LED drive voltages henrygb.

It does appear that the four LCD illumination Leds are driven a fair bit harder on the high setting in particular, than the keypad Led's. Interesting that on the Low and mid setting, there is very little difference in applied voltage between the two groups.

There is such a large variation in VF ratings between different manufacturers and even different color/brightness BINS within the same model from the same manufacturer in 0603 style LED's that it would be very difficult to get this right when you are trying to squeeze maximum luminus flux out of such a tiny LED.

These things are obviously being overdriven. The fix will either be to replace the LED's with another model with a slightly higher VF (possibly at the cost of slightly lower output/brightness), or modify the power supply circuit to reduce the voltage applied to these four Led's, which again will reduce the brightness slightly.

Regardless, it would be nice if Uniden could source a white led with a color temporature closer to 6000K instead of that god aweful 7000K+ blue/white that they seem to love so much.

I'm with boatanchor on this. It sounds like the LEDs are being overdriven causing them to fail (significant degradation in luminous output). Heat is the enemy of all electronics. I wonder if the design includes considerations for proper thermal management of these poor LEDs.

I also wonder if this white (grayish blue) backlight color selected for this radio is the most efficient and readable choice. I much more prefer the backlight color, intensity and general readability of the backlight on my BC125AT. It has a deep orange color. That would be the hot ticket to have the BCD536HP with that color of backlighting.

It would be some good data to determine if these LEDs are driven by a PWM circuit or not. It would surprise me if it didn't use PWM for brightness control. Getting scope plots at each display intensity level might provide insight into this issue.

Regarding the schematic, how about requesting just the portion that shows the display circuitry? Uniden owes us that much if they want the Radio Reference team to engineer a solution for them ;-)

 

[henrygb]

I have sent two of my 536s in for the dim display repair. It has only been four months and they are dimming again.

We know that Uniden replaces the diodes. We know that Uniden identifies them on the schematic as D415-D418. What we don't know is if Uniden has issued a ECO with a different diode. I don't think there's anyway we will know that unless Uniden tells us.

Maybe they are just changing the LEDs by other peers. Again, the recommendation is not to use the brightness at maximum intensity

Getting scope plots at each display intensity level might provide insight into this issue.

Regarding the schematic, how about requesting just the portion that shows the display circuitry? Uniden owes us that much if they want the Radio Reference team to engineer a solution for them ;-)

I can take readings with oscilloscope if necessary and if it's worth, I think it is not a pulse voltage that powers these diodes

 

[parnass]

.... I have noticed that there are LEDs in series I've marked in the picture, I've also taken the voltage value in some leds with different intensities dimmer. Take note that the maximum intensity voltage exceeds 3V, in the LED display , that might explain why these are damaged faster.

It is usually excessive current (or heat) which kills a diode. If the LEDs are in series, measuring the current and comparing it to the diode manufacturer's recommended ratings would tell us whether the circuit has sufficient current limiting.

It's difficult to measure the current because that would require desoldering one of the diodes. If there is a resistor in series with those 3 diodes, you could calculate the current by measuring the voltage drop across the resistor and using Ohm's law (I = V/R).

 

[nr2d]

I looked at other pics of the 536HP disassembled and the 1s at the beginning of this thread. Can you get
to the battery without completely disassembling the scanner? If so I'll just replace the battery. I can remember my Bearcat 210 had a 9 vdc battery to save the programming in the event of a power failure.

The battery on my 536HP failed a couple of weeks ago which I got on the 1st day it was released. But what's funny, know on wood, the battery in my 2nd 536HP which I purchased 2 weeks after the is still working great.

As for the LEDs both of my 536HP displays has dimmed a bit but isn't really hard to read even in radio room with the sun beating in through the window.

 

[darunimal]

"Can you get to the battery without completely disassembling the scanner?"
Yes the BCD536HP's outer shell(4 Philips screws) and inner (Upper 4 Screws and Lower 4 Screws) shell give you access to the internals of the scanner, lower breadboard and face plate, the serial flat wires connecting the breadboard to the face plate are glued in place (Uniden will be able to tell if you remove theses components and separate, definitely voiding warranty)

"If so I'll just replace the battery."
NO (I wish), the battery is soldered to the positive lead armature (I wish)

Replacing the battery circuit CRT
RTC = Real Time Clock. Also you are not replacing the battery circuit, you are replacing just the battery or you can do what I did

Retrofit a LiR 2032 onto a new Battery holder with the positive lead to the armature and the ground pin into one 3 holes on the of the bottom side of the breadboard, closest to the front of the scanner (the top of the breadboard is where every component is soldered in).
CRT = Cathode Ray Tube = a display screen formerly used as TV and computer displays, since considered obsolete, replaced by LCD, LED and plasma monitors and TV's.

I noticed in the second picture at the beginning of the thread, the ML414RU appears to be swollen, just like mine. So I'd believe it just a matter of time before the battery begins to leak acid on the breadboard making a Recall necessary and imminent, before permanent damage is done.

 

[kruser]

Just to be clear on this, the rechargeable version of the 2035 is the LIR2035 not the CR2035.
The CR2035 button cell is not rechargeable and will likely do some nasty damage to your expensive scanner if you try and install one.

That said, the specs on the original battery are pretty poor with only 1mAh of capacity and a rated cycle life of only 300 at a measly 10% discharge level. Increase the discharge level by leaving your scanner off for a few days each time and the cycle life would likely drop to only 150 or so. Under those conditions, it's not hard to see how/why the original button cells are failing in only 12-18 months.

A LIR2035 on the other hand has around 35mAh of capacity which, assuming it could actually be fully charged by the x36HP charge circuit, should backup the RTC at least 35 times longer and since the depth of discharge would be much lower under the same operating conditions, last a lot longer too.

Might be a practical option for the BCD536HP but I doubt that a LIR2035 would fit inside the BCD436HP

Question: Does the 536HP have the charging current necessary to properly charge an LIR-2032?

I originally added a 2nd cell similar to the small rechargeable cell Uniden uses in my 536HP and later, a 436.
I used the same rechargeable cell that Motorola used in their Advisor Elite series pagers.
Those pagers ran from a single AA 1.5 VDC battery but they contained a voltage doubler to create the 3+ volts needed to charge and maintain the memory retention lithium cell.

I found some similar in size to what Motorola used but they had solder tabs which made adding one very easy into a 4 and 536HP. I added it in parallel with the stock Uniden cell and have not had any RTC battery issues yet.
I did disconnect the added cell the other day as I worry the Uniden cell will fail and bring down my cell with it but both cells read about 3.2 VDC so they are still charging and maintaining charge.

I guess if I start having RTC issues, I'll know one of the cells has failed.

I don't think the LIR-2032 was made when I installed a 2nd cell of the same size as Uniden used but I'd be tempted to try one as long as I know the charging circuit is capable of the small current output that charges the Uniden cells.
I know the charging output is very low current so that's why I also ask if it is enough to properly charge a higher capacity LIR-2032 to capacity.

If so, I wonder how many hours the 536HP must be left on to fully charge an LIR-2032!

What is the charge/discharge cycle life on an LIR-2032?
I'd hope more than 300 cycles even though like you said, the discharge depth would not normally go that deep so it would not be a full discharge/charge cycle for most users.

I also wonder if leaving the 536HP on ALL the time affects the life of the Uniden cell? It's not like any heat is generated and the charging current is so low that I expect my answer to be no.

I have left my 536 on for over 3 months and the small rechargeable cells never exceeded about 3.2 VDC so I assume the charging circuit voltage does cut off at the correct voltage.
Actually, one can do the same test by disconnecting the cell and measuring the charge voltage. Being as there is no load on the charging circuit when the cell is disconnected, that test should provide the maximum voltage the cell may see in a radio left on all the time.

If I'm not mistaken, the max charge current on the small cells was rated in micro-amps on the ones I found specs for. I don't recall the max voltage though.

I've not looked up an LIR-2032 specs yet.

edit: I've also left my 536HP unpowered for about a month and the RTC cells still read about 2.95 VDC

 

[W8VI]

When the ML414RU battery stops working on my 536HP I was planning on replacing it with a more common CR2016 battery and external holder/socket that could be mounted in a variety of locations inside the scanner with double sided tape. From what I've read both batteries are 3 volt lithium's and the ML414RU has a capacity of 1.0 MaH where the CR2016 when charged is 90 MaH. The even more popular CR2032, 3 volt battery is rated at 220-240 MaH.

Other than the replacement CR2016 having more capacity available has anyone already done this mod and does anyone see a problem with it?

Thanks for the original post and great pictures!

73, Gary

 

[darunimal]

Yes I did the mod

http://forums.radioreference.com/un.../315640-retrofit-bcd536hp-rtc-keeps-time.html

 

[W8VI]

Thank you darunimal for the link and excellent pictures! I doubt you will ever have the RTC battery issue again and if you do - popping in a new battery will be a lot easier. Great job!

I'm somewhat surprised that the design team and engineers at Uniden did not foresee this issue and install a readily replaceable battery for the RTC. Where they that cost conscious that an additional 25 cents for a better battery and holder really mattered? Didn't anyone on the engineering team look at the battery and research its average life cycle?

In any event, it looks like a fairly simple project that most everyone who has done a little kit building and soldering can successfully complete.

 

[kruser]

When the ML414RU battery stops working on my 536HP I was planning on replacing it with a more common CR2016 battery and external holder/socket that could be mounted in a variety of locations inside the scanner with double sided tape. From what I've read both batteries are 3 volt lithium's and the ML414RU has a capacity of 1.0 MaH where the CR2016 when charged is 90 MaH. The even more popular CR2032, 3 volt battery is rated at 220-240 MaH.

Other than the replacement CR2016 having more capacity available has anyone already done this mod and does anyone see a problem with it?

Thanks for the original post and great pictures!

73, Gary

The common CR2016 or 2032 lithium cells are not intended to be charged period.
I'm not sure the 4 or 536HP models could provide enough charge current into the non rechargeable lithium cells is a question that I don't know the answer for but I would not advise charging either type cell even if the charge current is very low in the microamp range.

The LiR2032 is sold as a rechargeable cell and would work and should be safe but I sure would not attempt using the common CR/BR2016 or 2032's in a circuit that will supply charge current. When I added a similar sized (as Uniden's) rechargeable lithium cell into my 536HP in parallel with the OEM cell, the charge current was very low and well below the manufacturers specs for charging current. Uniden's charging circuit already supplied a max allowed voltage below the max voltage specs for those that sold rechargeable lithium cells so that also was not a concern.
When I did my mod by adding another cell in parallel with Uniden's cell, there were not many manufacturers that even sold rechargeable Lithium coin cells. The LiR-2032 was unheard of and about all that was out there were cells with about the same specs as what Uniden used.
The only equipment I knew of that used them were Motorola Advisor series pagers back in those days.
The rechargeable Lithium cells sold today use a different chemistry than your off the shelf non-rechargeable Lithium cells use.

Of course large items like laptop computers use rechargeable Lithium battery packs but those battery packs also contain very specialized charge monitoring and controlling circuits and most importantly, safeguards should something fail. Some even have safeguards for the safeguards but they do not always work as has been proven with laptop battery explosions.

Charging Lithium cells in not like charging NiMH cells but the technology is getting better. Even NiMH cells require proper charging circuits to be correctly charged.
Without those special circuits which usually monitor each individual cell, problems do occur as has been proven over and over by users whose expensive radios have melted down into an unrecognizable pile of melted plastic. Hence the reason that many do not recommend charging NiMH cells in the radio.

Read up on charging a normal non rechargeable lithium cell and you will find the warnings. Many of them.
Explosion of the cell is likely the number one reason against doing such.

On the other hand, many of the 35+ year old Icom rigs used a standard 2016 or 2032 and the original non-rechargeable lithium cells are still going strong today in many of those old Icom rigs like the R7000, R71A etc as well as the related HF transceivers.
Lithium cells generally carry a 5 to 7 year lifetime but the fact that many are still going strong even after 35+ years is thought to be simply because of the small amount of leakage current that will flow backwards through the very diode that prevents the cells from being charged.
If you take an old Icom rig that has sat in a closet for all these years, chances are that your lithium cell has long ago died.
It's the Icom rigs that have spent the last 35+ years plugged in with the memory circuit being powered where you will find the 35+ year old Lithium cells still maintaining a charge.
I think that's an unproven fact but it is indeed true. I own some that still have the original cells made in the 70's.
The leakage current through the diode that prevents the cell from charging is so small that is did not harm the cell and cause any damage.
I'm sure somewhere out there, someone has an old Icom rig that had damage from the cell being slowly charged all these years but I can't recall ever reading any stories about damage from reverse current leakage in the old Icom rigs.

Unless specifically made to be recharged, a lithium cell should never be charged.

If you do use a CR2032 or 2016 in a socket, I'd expect a pretty long time before the cells voltage goes low enough to no longer maintain the RTC. That would be due to the high cell capacity compared to the small cells Uniden chose but I'd install a diode in the circuit that prevents charging unless you are using one of the newer LiR 2032 rechargeable Lithium cells capability.
I still do not know if the 536HP even has the charge capacity to fully charge an LiR-2032 but someone did say leaving the 536HP turned on can and charging for something like 160+ hours would be sufficient to fully charge an LiR2032 cell.
I forget who said that and if that time was just an estimate or guess or based on actual tests with test equipment.

Use an LiR2032 instead as they are intended to be charged.
I doubt either model Uniden would ever exceed the LiR's max allowed charge current. The tiny cells Uniden uses in the x36 models are supplied by a very tiny amount of charging current which is why the long charging times already exist.

Just plopping a 2016 or 2032 into the circuit is a bad idea though as you are charging a lithium cell not intended to be recharged.
Not much different than charging an alkaline cell which will either rupture and leak eventually but charging a non-rechargeable Lithium is even more dangerous as you now risk explosion on top of any harmful leaking chemicals.

Both of which can ruin your expensive radio and also possibly cause a fire or bodily injury should it explode into your eyes for example.

So to answer your question, yes, there are reasons (several) for not recharging a CR or BR2016 or 2032 and other variations of non-rechargeable lithium cells.

You should also not directly solder to any lithium cell regardless if it is rechargeable or not. The heat needed can cause them to explode and if they don't explode, read the final cell voltage after direct soldering and you will find that your lithium cell may have lost a volt or so.
I've even seen lithium cells with solder tabs loose a volt or more when enough heat was needed to overcome a large ground plane area on a board with several layers of copper.
That's usually the result of using an iron of too low a wattage to properly heat the ground plane quickly though.

Batteries Plus used to spot weld solder tabs onto lithium coin cells so you could create custom voltage or capacity lithium packs.
They will no longer do such mainly for the explosion hazards even though spot welding a solder tab generates low heat for a very short time.

I'm not even sure they will spot weld solder tabs onto NiCD or NiMH coin cells any longer either but they will still spot weld solder tabs onto NiCD and NiMH AAA size cells or larger so they can create custom size packs for you. I don't think they will spot weld solder tabs onto any size Lithium cells at all today though.
They used to build up any size pack for you using your choice of battery chemistry but Lithium is out these days especially for coin or button cells.

 

[W8VI]

Thank you kruser for the information and the convincing reasons for using the rechargeable Lithium Ion battery. I will probably purchase the Maxell version ML2032 found on ebay:

New Maxell ML2032 Rechargeable 3V Battery Coin Cell Lithium Motherboard Camera | eBay

Or this one also looks interesting with the pre-welded connector tabs:

Li ion Rechargeable LIR2032 Coin Cell Battery w H Tab | eBay