BC-780xlt lightning strike

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kb0npw

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It has been a crappy evening. The most used piece of equipment in my hamshack took a lightning hit tonight. I heard the pop as the flash lit up the sky. The display on the 780 immediately started blinking on and off. I realized quickly that it was actually rebooting over and over.

If I turn the scanner off for a bit, I can turn it on and it will work fine for a short period of time. The characters on the LCD slowly begin to dim, and about 20 or 30 seconds after being powered up, the display goes blank, and it reboots. It then does this rebooting about once every 5 seconds.

I've taken it apart and I don't see any bulging caps or anything unusual. Does anyone have any ideas on where I should start? Is there a schematic available?

I checked the wall wart, and it is fine. I have hooked the scanner up to two other reliable power sources, and get the same results.
 

sjlamb

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It has been a crappy evening. The most used piece of equipment in my hamshack took a lightning hit tonight. I heard the pop as the flash lit up the sky. The display on the 780 immediately started blinking on and off. I realized quickly that it was actually rebooting over and over.

If I turn the scanner off for a bit, I can turn it on and it will work fine for a short period of time. The characters on the LCD slowly begin to dim, and about 20 or 30 seconds after being powered up, the display goes blank, and it reboots. It then does this rebooting about once every 5 seconds.

I've taken it apart and I don't see any bulging caps or anything unusual. Does anyone have any ideas on where I should start? Is there a schematic available?

I checked the wall wart, and it is fine. I have hooked the scanner up to two other reliable power sources, and get the same results.
If you lack the service manual and the expertise to do the work, I would suggest that you save yourself alot of time and trouble and simply send it off to Uniden for a "flat rate" repair.
 

kb0npw

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I think I will do that. The more I mess with it, the more confusing it gets. It seems as if the voltage which drives the LCD is dropping off. When first turned on, it runs fine for up to one minute. As it's scanning, the letters on the LCD begin getting dimmer and dimmer. The light stays bright. Eventually, as the letters get almost too dim to read, the unit basically reboots. After this first cycle, it then repeats everything about once every 5 seconds.
 

sjlamb

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I think I will do that. The more I mess with it, the more confusing it gets. It seems as if the voltage which drives the LCD is dropping off. When first turned on, it runs fine for up to one minute. As it's scanning, the letters on the LCD begin getting dimmer and dimmer. The light stays bright. Eventually, as the letters get almost too dim to read, the unit basically reboots. After this first cycle, it then repeats everything about once every 5 seconds.
Symptons indicate an internal short condition which is pulling down voltage to ground. Voltage regulator IC? Reverse Polarity diode? Zener diode shorted? One of 1,000 or better SMDs? Without a schematic and test point detail, you could ponder and guess all year and still get nowhere. Off she goes....
 

rmosier

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Sounds like a capacitor got cooked. Probably on the PCB board. As Sjlamb said, You'll need the service manual. If you don't have the test equipment, you'll need a tech that does.
 

DesertRatt

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Surge Protector

First, I'm not an employee of the Grove Enterprises. Second I have one of these between my scanner station and my outdoor antenna. Its a small price for some piece of mind. While nothing is 100%. This is better than nothing.

Surge Protector
 
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kb0nly

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Impulse Suppresors | Arrestors

One of the best out there... I have seen repeater sites take a direct hit and turn the ICE box into a baby rattle and the connected equipment keeps going like nothing happened.

Polyphaser units cost a LOT more but they are ok... I have seen to many of them fail when they shouldn't. In the commercial industry they replace them annually regardless of testing good. Ever wonder why you see all those used Polyphasers on eBay? They are maintenance pulls. I've talked to guys in the cellular industry, i was told about the box of used units in the shop. I offered them a case of beer for them so i could sell them on eBay for spare cash... LMAO

I have these.. Mainly due to lower cost than the ICE units. But i will be swapping them out, maybe one at a time as i can afford to, for the more robust ICE units.

Jetstream

The Jetstream units are the same as the Alpha Delta or Diamond models, just a gas discharge arrestor.

Also make sure you antenna is grounded well, the tower or mast and support as well. A nearby strike shouldn't have killed it that easy if it was properly grounded and protected. Could have been a power surge also, was the wall adapter plugged into a surge arrestor?? I power all my scanners and radios off the whole shack DC supply and battery backup. The AC power to which is surge protected. I also have a whole house surge arrestor installed at my service panel, and UPS's on the computers and my bigscreen tv.

We get our share of brownouts and surges here. I also have a generator for those really bad days... LOL

Ok... Enough of that... As for the condition the scanner is in now....

I had an old scanner that took a surge do something similar, after being on a while the regulator would get hot and output would drop off and the voltage would get low enough for it to shut off or cycle off and on. Turned out to be a bad filter cap that would draw too much current for the regulator and then the voltage would drop. If i was troubleshooting it i would start at the power jack and trace my way in from there, caps and regulators along the way. Turn it on and see if anything gets hotter than normal, etc.

Have you tried powering it with something other than a wall adapter with a fuse inline? The reason i ask is the wall adapters don't have an inline fuse and the voltage sags if you pull more current than its rated for. Plug it in to a larger supply with an appropriate rated fuse, i think the wall adapter on my 785D is a 500ma, so get a half amp fuse, does the fuse pop? If it does then its definitely a power problem as its pulling too much current. Or if you have an ammeter check to see what the scanner is drawing for current also.
 

DaveIN

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I wouldn't waste any money on a diagnosis for repair. I'd really be surprised if it can function correctly even if a few components could be replaced. If the CPU has damage, it's all over. You may be able to get some cash for parts however. This is based on past experience with a direct lightning strike.
 
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kb0nly

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I dont think the CPU is at fault though... And if it was a direct strike i suspect he would have lost other stuff in his shack as well.
 

DesertRatt

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First, I'm not an employee of the Grove Enterprises. Second I have one of these between my scanner station and my outdoor antenna. Its a small price for some piece of mind. While nothing is 100%. This is better than nothing.

Surge Protector
I should also add that I have a grounding block outside with a 8' grounding rod in the ground.
 

kb0npw

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Thanks for the continuing comments and advice. It's much appreciated. I have been tinkering with it more, and have found that if I swap out the original wall wart for one with lower voltage, the LCD lettering stays crisp, and it no longer has the rebooting problem.

Since posting this, I have discovered that the scanner will no longer connect to Proscan, so it's com port capabilities have been fried. I've also noticed that it seems to have issues with opening the squelch on some channels. Overall,it just acts squirrelly. I hope the flat rate repair at Uniden covers everything that is wrong with it, because it looks like this baby needs a handful of parts.

I have made up my mind to pull the plugs on everything when it storms until I can get my grounding system up to snuff. My tower has an 8' ground rod, but it is not tied to the electrical service ground. I know I need to accomplish that ASAP. Until then, I'm playing russian roulette with mother nature and her fury.
 
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