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Pro-668: Potential battery killer!!!

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aggie72

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I picked up a PRO-668 from a seller on Amazon complete with box and all accessories. The SIMM looks like it had been formatted so I didn’t have the OEM software but easy to get off the web. Anyway, I loaded brand new NiMH batteries making sure the switch was set to the same in the battery compartment and everything was working fine except I noticed that the battery indicator was only showing about half charge. I checked the batteries and they were fine. I figured something had to be wrong so I took it to the work bench and found out that even when the scanner was off the battery drain was around 280 mA! I opened it up and didn’t notice anything unusual. I knew something had to be getting warm so feeling around on the circuit boards I noticed a warm spot on the underside next to the speaker. It was had to see so I had to pull the board out and noticed a rather large surface mount cap had turned into a piece of charcoal and it was the culprit for sure – very warm to the touch. It appears that this cap is connected directly across the battery terminals. There is no indication what the value is but I suspect it to be an electrolytic. I can only surmise that someone installed some batteries incorrectly which caused the cap to fail. Diode protection probably saved the rest of the scanner. Unfortunately the cap turned into a big resistor that was pulling current from the batteries. I removed the cap and left it off. I don’t see any need for it since USB power is very well regulated.

There was an additional problem I had to deal with. When I took the boards apart there were several quick connects – a large multi-connector and two power connectors. One of the power connectors was missing the ground pin – there was probably enough ground connectivity with the other connectors that it didn’t interfere with the scanner but I wanted to fix that problem. I removed what was left of the old connectors and just solder wire connections.

There was another issue that I thought might be a problem. The keypad used a flat flex connector that inserted into a socket on the board. When I removed it to work on the scanner there was small bits of white plastic all over the place. It looks like very bad quality stuff and I was afraid that it might cause some continuity issues. I cleaned it up the best I could and so far no problems.

Once it was back together I measured the vitals again and got:

2 mA – scanner off
7 mA – scanner on and idle
200 mA – scanner in search mode
230 mA – scanner locked on station and receiving

I also measured the charge circuit: 8 volts @ 45 mA. This may take a long time to charge completed discharged batteries so I would use a dedicated charger for NiMH batteries. When the switch is in alkaline position no charge is applied.

Anyway I wanted to point this out in case anyone else is noticing poor battery performance on their Pro-668.


I hope this helps.


John
 

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SCPD

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#2
So the purpose of this is to show you bought a bad scanner with Pc board damage or
That we should remove Capactor C401 so that ours doesn't end up charred???Thank you for the pictures.
 

16b

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#3
So the purpose of this is to show you bought a bad scanner with Pc board damage or
That we should remove Capactor C401 so that ours doesn't end up charred???Thank you for the pictures.
Did you actually read the post or just look at the pictures? You can figure out the purpose of the post if you read it.

To the OP: thanks for writing up your findings and including high quality images. I do not own one of these scanners but have benefited from many similar posts about different products, some that were posted many years ago. I am sure it will help others who are having the same problem.
 
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#4
So the purpose of this is to show you bought a bad scanner with Pc board damage or
That we should remove Capactor C401 so that ours doesn't end up charred???Thank you for the pictures.
. I understand his post. I may buy a 668 in the future but I will use an external charger as well. I agree, nice pics too.
 

SCPD

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#5
yes

Did you actually read the post or just look at the pictures? You can figure out the purpose of the post if you read it.

To the OP: thanks for writing up your findings and including high quality images. I do not own one of these scanners but have benefited from many similar posts about different products, some that were posted many years ago. I am sure it will help others who are having the same problem.

Although I didnt benefit from your post,I may have did from Aggie72's......
I am asking if the capacitor in question is better off not being put back? Yes or no?
I am asking this because it says it still draws current with the scanner Off.
 

aggie72

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#6
Although I didnt benefit from your post,I may have did from Aggie72's......
I am asking if the capacitor in question is better off not being put back? Yes or no?
I am asking this because it says it still draws current with the scanner Off.
Having the cap connected directly to the battery has the potential of shorting the battery supply as it did in my unit. I would feel better if the cap was behind a switch but in this design I feel safer removing the cap all together. I really don't see a need for it. If you wanted some common mode rejection then maybe a 0.1 uF but not anything bigger than that. That's just my 2 cents worth.

John
 

SCPD

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#7
thanks

Having the cap connected directly to the battery has the potential of shorting the battery supply as it did in my unit. I would feel better if the cap was behind a switch but in this design I feel safer removing the cap all together. I really don't see a need for it. If you wanted some common mode rejection then maybe a 0.1 uF but not anything bigger than that. That's just my 2 cents worth.

John
Thanks so much John,I appreciate the reply!
I really like the Pro-668 and I plan on holding onto them.
 
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#8
:eek: WOW, interesting post. Could I surmise that alkalines were inserted while the switch was in Ni-MH (rechargeable) position? Am almost curious to open mine up and look for similar 'damage' or potential problem in these areas. Already recharging all my Ni-MH's OUTSIDE the radio, as there are enough posts demonstrating the poor quality results from the built-in charger. :eek:
 

SCPD

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#9
I can tell you I had a set of 2400Mah duracels only last 1 year exactly from charging inside the scanner.
 

DonS

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#10
2 mA – scanner off
7 mA – scanner on and idle
200 mA – scanner in search mode
230 mA – scanner locked on station and receiving
Are those numbers battery drain or draw from an external supply?

I ask because the drain from the batteries, no external supply connected, scanner off, should be on the order of a few microamps (I just measured mine at ~9 uA), not 2 milliamps.

Also, the "7 mA - scanner on and idle"... are you missing a zero? It should be about 60 mA with no backlight. The CPU and uSD card take that much (could vary +/- 20mA or more depending on the uSD card). In any case, 7 mA seems suspect.

Here's how I tested (WS1088, but it's the same as a PRO-668):
* batteries in external holder (from a PSR-500)
* battery holder connected to scanner battery terminals
* Fluke 289 in series
* power on...
* powered on, at main menu, all backlights off = 59.4 mA
* press/hold power button to power down = 8.79 uA
 

aggie72

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#11
Are those numbers battery drain or draw from an external supply?
I'm glad someone is checking those numbers. I used a bench supply and these figures are the same with batteries. What ever blew the cap probably did some damage to the power supply/charging circuit. If you are certain on those numbers then I'll have to dig into the scanner a bit more which is a pain considering it's mostly not serviceable :(
 

SCPD

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#12
if

I'm glad someone is checking those numbers. I used a bench supply and these figures are the same with batteries. What ever blew the cap probably did some damage to the power supply/charging circuit. If you are certain on those numbers then I'll have to dig into the scanner a bit more which is a pain considering it's mostly not serviceable :(
If you give up on it,can I have a crack at it?I love fixing stuff.:D
Used to work at a place that fixes stuff other places cant,they also fixed stuff for Best Buy's and other chain stores.
 
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