BCD536HP Date and Time reset.

[kruser]

I thought I'd read they replaced the old BT1 cell with a super cap located elsewhere on one of the boards. Backtracking any voltage present on the unused BT1 pads may be the best bet if they didn't cut those traces out of the circuit on the repaired models.

 

[donc13]

OK, the mod should work for you. I'm in another boat. I have two radios...both with no battery on BT401. One keeps time, the other doesn't. What kind of witchcraft are they using now to back up the clock?

I am presuming you keep a battery in both. Doesn't have to be fully charged

Again, I don't know this for a fact about uniden scanners, but a lot of electronics use an electrolytic capacitor to store the tiny amount of power needed to keep a modern RTC chip going for a month or so. As has been mentioned by others, those capacitors can fail with no visible sign that it's failed making it difficult to troubleshoot.

 

[gary123]

If the cap has failed as mentioned by dave3825. If your pulling it to test you might as well replace it with a new known good part. Its the same amount of soldering.

Donk13 thanks for the nice .pdf. Obviously someone had access to a service manual even if it was just a digital version. My units do not have the battery but if I was doing the repair I would be installing the LIR2032 (rechargeable) as n4txf suggests. I will see if I can locate the keep alive cap next time I crawl inside a unit.

For anyone brave enough if you want a custom colored background you can change out the backlight LEDs D415, D416, D417 and D418 with color versions such as orange, green blue. But I do not want to hijack the tread.

 

[morrisr3nd]

I'll tell you one thing. Those resistors are super SMALL. It's going to be an interesting feat to do. I'll have to use my extra super magnifying glasses with microscope to pull this off. Parts have shipped so we will see how this goes.

 

[n4txf]

I thought I'd read they replaced the old BT1 cell with a super cap located elsewhere on one of the boards. Backtracking any voltage present on the unused BT1 pads may be the best bet if they didn't cut those traces out of the circuit on the repaired models.

My thinking too. But...
I have two BCD536HPs, both have NO battery in the BT401 spot, yet one keeps time, the other doesn't. There are no major caps on the front PCB. There is one large attractive cap that had my attention on the main PCB at the BT1 spot. See pics. Its an Elna, 3.6v, 1.5F cap. I checked the voltage on the good radio and the time failing radio. They both measure 2.97vdc when powered on and both drop to 2.83vdc when unplugged, but only one clock resets. Goo figure. Also...can't find and exact replacement for the super cap. Can only find 3.6v in 0.47F and 1F sizes. Uniden Parts Dept refused to help. : (

 

[n4txf]

I'll tell you one thing. Those resistors are super SMALL. It's going to be an interesting feat to do. I'll have to use my extra super magnifying glasses with microscope to pull this off. Parts have shipped so we will see how this goes.

Hey, tell me if you have this large super cap on the "BT1" spot on the main board.

 

[kruser]

Hey, tell me if you have this large super cap on the "BT1" spot on the main board.

I think that super cap in your pic was part of the RTC fix. I've not opened my new or old original unmodified 536 however but will if either ever fails.
What I don't recall for certain but kind or remember UPMan mentioning that there was also a possible change to the RTC circuit or components so the RTC circuit did not draw so much current.
Heck, I have mechanical wrist watches that use 1.5 VDC batteries which last in those watches for over two years!
A RTC circuit in a scanner should run for a very long time on the original tiny lithium cell used in the original x36HP models. Was the failure simply a bad batch of lithium cells or rather a design flaw in the RTC circuit causing it to draw excessive current? I think the excessive current draw may have been the culprit myself.

 

[n4txf]

Well, well, well. Looks like the "BT1" Elna 3.6v 1.5F Cap is the issue. I let both radios sit overnight and tested voltage in AM. My working radio's cap held 2.94v and the time. The other radio's cap dropped to 1.3v and lost time of course. The next trick is finding the components. IF you can find the right value cap, it's out of stock, overseas with a 6-8 week ship time and very proud of the caps. I did find two in Texas on ebay. I should receive them this weekend. I'll advise of my progress. Thanks all for the brainstorming!

 

[morrisr3nd]

Wrong cap. Sorry.

However I did find a 3.5 V 1.5F in stock HERE.

 

[gary123]

You can use a larger value cap if you can find one that fits. I do not suggest people start randomly replacing parts with different values this is a special circumstance. so CYA time do it at your risk.

Think of the 1.5F like a bucket. The larger the number the larger the bucket. NOTE: this is 1.5F not a 1.5 uF. You do not need a swimming pool. Two 1F caps in parallel would give you 2F.
reference not an endorsement.

Series and Parallel Capacitors | Capacitors | Electronics Textbook

Read about Series and Parallel Capacitors (Capacitors) in our free Electronics Textbook

www.allaboutcircuits.com

 

[n4txf]

Wrong cap. Sorry.

However I did find a 3.5 V 1.5F in stock HERE.

I have two 3.6v, 1.5F caps coming...a little different pin design, but should work. I'll post results.

 

[n4txf]

OK...got the new super caps...same exact value. Different pin pattern, but easy to overcome. Left radio on for over two days to charge the new caps. Got up to 2.96v...just like my working radio. Turned off for 10 secs...OK. Turn off for greater than 10 secs...reset clock. No joy. Back to square one. Still can't justify burning $100 to send to Uniden. Any ideas? Someone else has to had experienced this.

 

[morrisr3nd]

I replaced my small button cell with the LIT2032 yesterday. It's only been charging for about 26 hrs. I'll let you know tomorrow how it works. I also attempted to change the resistors and LED's but couldn't get the solder to melt on those small turds. I'll give it another shot when I find out if my other fix works. My hands aren't as steady as they were at 30.

 

[n4txf]

I replaced my small button cell with the LIT2032 yesterday. It's only been charging for about 26 hrs. I'll let you know tomorrow how it works. I also attempted to change the resistors and LED's but couldn't get the solder to melt on those small turds. I'll give it another shot when I find out if my other fix works. My hands aren't as steady as they were at 30.

Try to snap a shot of your main PCB board. I'm curious to see the difference. Surprised I can't find a pic of any BCD536HP main PCB board anywhere on the web.

 

[morrisr3nd]

Sorry, Pictures are not very clear. I tried to send straight from my phone but of course the file size is too large. Don't know exactly how to fix that but I'll try. I did do my battery modification and it seems to be working. I let it stay on charge for 48 hours. I took it off and left it off for a bit. That's when I took these pics. Plugged it back in and didn't have to reset the time. So far so good.

 

[morrisr3nd]

Does anyone have pics of the inside of a FIXED 436HP with Date/Time Mod? I'd like to see what they changed to make that work. I don't know if I have enough room for another battery in there.

 

[morrisr3nd]

Let's see if this is any clearer.

 

[n4txf]

Sorry, Pictures are not very clear. I tried to send straight from my phone but of course the file size is too large. Don't know exactly how to fix that but I'll try. I did do my battery modification and it seems to be working. I let it stay on charge for 48 hours. I took it off and left it off for a bit. That's when I took these pics. Plugged it back in and didn't have to reset the time. So far so good.



View attachment 137975




View attachment 137974View attachment 137976

 

[n4txf]

Good job. Thanks for the pic. Here's my comparison. Looks like my Super Cap is the big difference on the main PCB. I replaced with same value...not fixed. Either I have another issue...or TWO issues.