Power/Charging Circuit Fried

[davidmc36]

I sort of hi-jacked another thread talking about this so I thought it would be apporpriate to do a new thread.

I recently did the firmware update to my BC246T. After I was done it would not accept power from the wall-wart. I confirmed by using a meter that there was power and even tried another wall wart "just to be sure".

Although it had nothing to do with the firmware itself, I think that the process of how you get into and out of update mode caused my problem. At one point it seemed like it was just coincedence but upon reflection I believe that is not the case.

When you have finished uploading the update the update program pops up a screen that says "Turn off power and disconnect your scanner" or something to that effect. If you press the power button in the normal way to turn it off, nothing happens. So you need to pull the power plug. I foolishly pulled the plug out of the scanner instead of pulling the wall wart out of the wall. I will bet a truck-load of money that is what fried something inside the scanner. I should have known better expecially after recently installing an Xplornet dish and the instructions in there specifically tell you to unplug from the wall, NOT THE MODEM, to do a power cycle. You can get quite a spark at the plug when you pull it out.

Too bad the updater screen that pops up did not say something like that as a little reminder to not get hasty and take the time to stoop down and pull it out of the wall.

Oh well, live and learn. At least it still runs on batteries. I was using an external charger 90% of them time anyway while travelling.

 

[kellykeeton]

there have been a lot of power issues lately with the 396/246 was there any change to the power inthe updates?

So here was my experience, I flashed the firmware and didnt plug it in, did from batt's when it was done I had a blank screen and cant use the power button so I pulled a battery. radio boots up just fine

I just recently charged my radio and after charging the next morning the radio was hot, I have never had the radio feel hot when charging (OEM batteries and switch is on nmhi)

my radio still seems to work fine with batts no batts wall wart no wall wart (for now)

I hope there isnt a rash of firmware related power transformer crashing going down.

anyone try downgrading to see if firmware is related?

 

[davidmc36]

I never tried a downgrade but UPMan replied in the other thread and said there was nothing in the firmware to do with the power circuit.

 

[Viper43]

Firmware shouldn't affect the power in the 396T at all, I'd look at:
The age of the batteries
The walwart - make sure it's outputting 6v 800Ma

V

there have been a lot of power issues lately with the 396/246 was there any change to the power inthe updates?

So here was my experience, I flashed the firmware and didnt plug it in, did from batt's when it was done I had a blank screen and cant use the power button so I pulled a battery. radio boots up just fine

I just recently charged my radio and after charging the next morning the radio was hot, I have never had the radio feel hot when charging (OEM batteries and switch is on nmhi)

my radio still seems to work fine with batts no batts wall wart no wall wart (for now)

I hope there isnt a rash of firmware related power transformer crashing going down.

anyone try downgrading to see if firmware is related?

 

[slicerwizard]

I foolishly pulled the plug out of the scanner instead of pulling the wall wart out of the wall. I will bet a truck-load of money that is what fried something inside the scanner.

And you would lose that truckload of cash. You jump to conclusions based on, well, as near as I can tell, a poor understanding of how things actually work. You ignore the fact that the equipment was designed to be used that way and that thousands of users do use it that way every day without incident. The more plausible explanation - that some internal component (like a solder joint on the power jack, for example) just chose that moment to fail - doesn't even register on your radar.

The 246T's power circuit is robust enough to run the scanner on input voltages ranging from 6 volts to at least 12 volts, but it can't handle removal of power at the jack? That turkey ain't gonna fly.

 

[davidmc36]

And you would lose that truckload of cash. You jump to conclusions based on, well, as near as I can tell, a poor understanding of how things actually work. You ignore the fact that the equipment was designed to be used that way and that thousands of users do use it that way every day without incident. The more plausible explanation - that some internal component (like a solder joint on the power jack, for example) just chose that moment to fail - doesn't even register on your radar.

The 246T's power circuit is robust enough to run the scanner on input voltages ranging from 6 volts to at least 12 volts, but it can't handle removal of power at the jack? That turkey ain't gonna fly.

Already had the power jack removed and re-soldered onto the board and no change. Even tried soldering wires straight to the board when I was in there and no dice. As near as I can tell you are jumping to conclusions based on a poor understanding that other people may be as intelligent as you and in some cases more intelligent. You are ignoring the fact that as I explained, some equipment specifically tells you NOT to unplug from the unit but go to the wall. The more plausilble explanation that I was simply trying to pass along something might help somebody avoid a possible pitfall does not even register on YOUR radar!

 

[davidmc36]

The 246T's power circuit is robust enough to run the scanner on input voltages ranging from 6 volts to at least 12 volts, but it can't handle removal of power at the jack? That turkey ain't gonna fly.

Looks like you have a poor understanding of how things work. Did you miss the lable on the back of the 246 PRINTED IN RED no less, "......12V or incorrect polarity will damage the scanner"

 

[UPMan]

Simply unplugging an AC adapter from the radio will not harm it. I would mark this event in the "unfortunate coincidence" column (whatever component failed, happened to fail at just the right time to make it seem there was an association with the update...).

 

[davidmc36]

Simply unplugging an AC adapter from the radio will not harm it. I would mark this event in the "unfortunate coincidence" column (whatever component failed, happened to fail at just the right time to make it seem there was an association with the update...).

As I clarified in the OP, I do not believe it was associated with the "update" per se, but the physical act of pulling the plug out with no other power source in the scanner to buffer the curent surge as the plug comes out which can cause a spark, I have seen it happen even with low voltage things like that wall wart and that surface mount stuff is REALLY tiny, and designed to run on very small current draw, hence the ability to make things very small and low draw on the batteries.

It VERY plausible that pulling the plug like that caused it.

 

[MarkEagleUSA]

some equipment specifically tells you NOT to unplug from the unit but go to the wall.

I don't recall seeing that advice anywhere in the 246 documentation.

Simply unplugging an AC adapter from the radio will not harm it.

About as expert as you can get.

As I clarified in the OP, I do not believe it was associated with the "update" per se, but the physical act of pulling the plug out with no other power source in the scanner to buffer the curent surge as the plug comes out which can cause a spark

The 246 likely has the proper "buffering" in its power/charging circuit. If I remember correctly, the 246's wall-wart in non-regulated (most wall-warts aren't) so it doesn't provide stable voltages to begin with.

I have seen it happen even with low voltage things like that wall wart and that surface mount stuff is REALLY tiny, and designed to run on very small current draw, hence the ability to make things very small and low draw on the batteries.

Just because SMT devices are very small doesn't mean they aren't robust.

It VERY plausible that pulling the plug like that caused it.

It is plausible, though I wouldn't say "very". I'm not an electronics expert, but I don't think the standard DC power plug and jack can short during insertion or extraction. The one question in my mind is are you sure you used the proper wall-wart?

 

[davidmc36]

I don't recall seeing that advice anywhere in the 246 documentation.

About as expert as you can get.

The 246 likely has the proper "buffering" in its power/charging circuit. If I remember correctly, the 246's wall-wart in non-regulated (most wall-warts aren't) so it doesn't provide stable voltages to begin with.

Just because SMT devices are very small doesn't mean they aren't robust.

It is plausible, though I wouldn't say "very". I'm not an electronics expert, but I don't think the standard DC power plug and jack can short during insertion or extraction. The one question in my mind is are you sure you used the proper wall-wart?

Yes using the original wall wart. I didn't say that the 246 manual had that warning in it, I said some devices, one of which is the Xplornet dish that I just set up, and I have seen others. Yes Surface mount devices are inhernetly robust but anything can get fried by over current and the small current that they are designed to run on would naturally mean that the current reqd to fry them is that much smaller. I am not disputing UPMan's expertise, I just think it is possible that it happened the way I think. "Very" was a bit of an exaggeration. As I said I have seen sparks jump with these type of wall warts. All I wanted to pass along was that it is probably a good practice to go to the wall instead of the unit. I don't see how that bit of advice can be disputed. No question it could be coincedence that it failed just then.

 

[Viper43]

I have 75+ wall warts and never saw any of them spark removing them or plugging them in. I'd look for a failed diode in the power circuit though, most likely any voltage spike came through the poerlines and it would be a trillion to one unpluggng the wal wart would do anything.

V

 

[davidmc36]

I have 75+ wall warts and never saw any of them spark removing them or plugging them in. I'd look for a failed diode in the power circuit though, most likely any voltage spike came through the poerlines and it would be a trillion to one unpluggng the wal wart would do anything.

V

Are you speaking of a diode in the rectifier of the wall wart? Are you thinking enough reverse voltage could cause you some grief? It never occured to me that it could have been it. I checked the output of the wall wart and it was about 8.2 volts no load which seemed reasonable to produce 6v at 500ma, without calculating anything out. That was on a digital meter. I should dig out an analog one and see if there appears to be any ripple.

 

[MarkEagleUSA]

Are you speaking of a diode in the rectifier of the wall wart?

The diode is in the charging circuit of the 246. It's primary purpose is to protect against incorrect polarity.

 

[davidmc36]

The diode is in the charging circuit of the 246. It's primary purpose is to protect against incorrect polarity.

IC so if it were gone then no power through. Problem is, it is not really practical for me to try and do anything about it. It was a tricky job with my smallest soldering iron to remove and re-install the power jack. Surface mount diodes, caps, resistors and the like are nearly impossible by hand. If I did have a schematic I could take it to the guys in the avionics shop with their microscopes and tools they use while looking through them, but I am sure a schematic is unattainable. I am willing to live with the external charging solution since that is what I do 90% of the time with it on the road. I just thought I would share my experiences in case it may save sombody else some grief.

 

[slicerwizard]

Looks like you have a poor understanding of how things work. Did you miss the lable on the back of the 246 PRINTED IN RED no less, "......12V or incorrect polarity will damage the scanner"

Do you still have a working 246T AC adapter? Measure its output voltage.

IC so if it were gone then no power through.

No. If it were "gone" (failed open) you would lose the reverse polarity protection.

If it failed shorted (which is what it would do), you wouldn't be able to get any external power into the scanner. And you'd severely stress your AC adapter.

 

[davidmc36]

As I said 3 posts above 8.2 volts, no load. Without doing the actual calculations, I expect that should work out to 6volts at 500ma.

Ummmmmmm.......wouldn't that be the other way around, failed open will not allow flow in either direction and failed shorted will allow flow both directions?

 

[slicerwizard]

As I said 3 posts above 8.2 volts, no load. Without doing the actual calculations, I expect that should work out to 6volts at 500ma.

Well there's your problem - unregulated adapters don't drop a mere volt or two when you fully load them. An unloaded 246T AC adapter (model AD-0008) puts out 11.5 volts (and 8.8 volts while powering an unsquelched backlit scanner). If yours is only feeding 8.2 volts to your multimeter, it's toast. If you want to verify it, strip a bit of insulation off both conductors and measure the voltage as you try to power up the scanner (or some other 20 to 30 ohm load). I recommend making the incisions close to the AC adapter so as to keep the rest of the cord (which is the only useable part of your adapter now) in good shape. Make the two nicks an inch apart to avoid any shorts.

Once you've verified that your AC adapter is a basket case, build yourself a 5 to 9 volt supply (4 alkaline or NiMH AA cells in a holder will do fine) and use the cord from your AC adapter to power up your 246T. Just cut the cord a few inches from the dead adapter and wire it in to your battery stack. Verify the polarity at the plug with your meter before you power your scanner. Remove the batteries from the scanner and hook up your external supply. It will show whether your 246T's power circuit is working or not.

Ummmmmmm.......wouldn't that be the other way around, failed open will not allow flow in either direction and failed shorted will allow flow both directions?

Nope. Both ends of the diode are connected directly to the DC jack.

 

[davidmc36]

Well there's your problem - unregulated adapters don't drop a mere volt or two when you fully load them. An unloaded 246T AC adapter (model AD-0008) puts out 11.5 volts (and 8.8 volts while powering an unsquelched backlit scanner). If yours is only feeding 8.2 volts to your multimeter, it's toast. If you want to verify it, strip a bit of insulation off both conductors and measure the voltage as you try to power up the scanner (or some other 20 to 30 ohm load). I recommend making the incisions close to the AC adapter so as to keep the rest of the cord (which is the only useable part of your adapter now) in good shape. Make the two nicks an inch apart to avoid any shorts.

Once you've verified that your AC adapter is a basket case, build yourself a 5 to 9 volt supply (4 alkaline or NiMH AA cells in a holder will do fine) and use the cord from your AC adapter to power up your 246T. Just cut the cord a few inches from the dead adapter and wire it in to your battery stack. Verify the polarity at the plug with your meter before you power your scanner. Remove the batteries from the scanner and hook up your external supply. It will show whether your 246T's power circuit is working or not.


Nope. Both ends of the diode are connected directly to the DC jack.

That's not the adapter that I have. I have P/N AD-1017, switching power supply. I tried it out on a partially charged 4 cell NiMH and it drops to about 5 volts, 5.1....5.2.....5.3......5.4...... after watching it for ten or fifteen seconds.

Are you saying that the diode is across the neg and pos terminals of the power jack? So if it were shorted the power goes through the diode instead of the scanner, just as if you fwd biased it in a reverse polarity situation?

 

[davidmc36]

Once you've verified that your AC adapter is a basket case, build yourself a 5 to 9 volt supply (4 alkaline or NiMH AA cells in a holder will do fine) and use the cord from your AC adapter to power up your 246T. Just cut the cord a few inches from the dead adapter and wire it in to your battery stack. Verify the polarity at the plug with your meter before you power your scanner. Remove the batteries from the scanner and hook up your external supply. It will show whether your 246T's power circuit is working or not.
QUOTE]

Tried a four cell pack and no dice.

Tried a 7.2 sub-C ni-cad pack too, no joy. I'm not gonna screw with it any more. Next thing you know it won't work at all. Just have to be happy with external charging.

The one queer thing is that it will still go into firmware upload mode using the original wall wart.