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Old 11th May 2021, 10:35 am   #1
Malcolm T
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Default Antenna analyzer battery fault

I have just dug out a piece of kit that had been stowed away for several years.
Reason, it failed to work !
But i looked at it and done some basic fault finding and found an SMD fuse had blown.
Not having the correct rated fuse i stripped out a very small diameter length of wire from some flex, almost invisible. Soldered this across the pads and hey presto it works again.
However there remains a mysterious fault of 160ma drain from the power cells when the unit is turned off , the switch is not mechanical like a toggle , it is mounted on the pcb, more like a button.
Does anyone have any suggestions as to what might be the fault on this SMD component board unit.
Would the unit have any reason to draw current even when off . or has something gone a kind of semi short .
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Old 13th May 2021, 8:57 am   #2
Herald1360
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Default Re: Antenna analyzer battery fault

How long is this piece of string?

What exactly is the make/model of the analyser? Have you any circuit information?

What is the normal running current of the device? Is 160mA a large or small amount relatively speaking?

Does the pushbutton switch the supply directly or does it just supply a control signal to an electronic switch?

Are there any components such as capacitors which are directly across the power rails regardless of the ON/OFF state of the unit?

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Old 14th May 2021, 9:55 am   #3
Malcolm T
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Default Re: Antenna analyzer battery fault

Thanks for your reply
Funny you should mention a circuit diagram, sadly not supplied with the equipment , but i have made a note of all the specific active components so should be able to come up with a block diag.
The unit is a WE-030 A, i don't think very many sold , its UK made by water beach electronics.
I was also wondering of the unit is on constant standby but that might be crazy as the battery capacity is only about 4 hours continuous , so i think there is a drain somewhere. As you say capacitor / component across supply i will check that out. Perhaps a cap has developed a kind of semi short ?.
When i plug in the charger it seems to charge up the NiMh batteries fine.
I will check the running current too.
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Old 14th May 2021, 11:35 am   #4
chriswood1900
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Default Re: Antenna analyzer battery fault

Details can be seen here https://www.waterbeachelectronics.com/WE-2705P_data.pdf
160mA seems very high for a small handheld device with only an 1,800 mAh battery and I would expect to see a few micro amps when on standby.
Time for some testing and voltage checks.
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Old 14th May 2021, 12:22 pm   #5
Malcolm T
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Default Re: Antenna analyzer battery fault

Thanks for the info.
Yes testing times i think !.
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Old 14th May 2021, 11:13 pm   #6
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Default Re: Antenna analyzer battery fault

The linked- spec says:

Battery: 3.7V 1800 mAH LiPo 103450
Operational time: > 6 hr continuous

So that would make the operating current < 300mA, and could well be that it's not actually switching-off. And could try measuring the current when it's on, to see if it changes much.
It might be that only the display / backlight is being switched-off and there is a shorted transistor power switch to most of the circuitry.
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Old 14th May 2021, 11:26 pm   #7
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Default Re: Antenna analyzer battery fault

I would contact the manufacturer and ask the questions, hopefully they will provide some info as to possible fault https://www.waterbeachelectronics.com/contact.html
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Old 15th May 2021, 9:13 am   #8
Malcolm T
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Default Re: Antenna analyzer battery fault

Going to have to dig into this further and also contact the manf'r as well then.
Well the power is going somewhere. Just an irritating fault.
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Old 15th May 2021, 9:33 am   #9
Malcolm T
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Default Re: Antenna analyzer battery fault

Never having done any SMD component testing before is there any danger of blowing a chip or microprocessor when using a multi meter for on the board fault finding ?.
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Old 15th May 2021, 10:31 am   #10
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Default Re: Antenna analyzer battery fault

Probably no more than with normal components but a steady hand and some needle probes (or modified scalpels!) won't go amiss. A "tweezer" probe for probing both ends of resistors and other two terminal components simultaneously is also handy.
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Old 15th May 2021, 12:10 pm   #11
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Default Re: Antenna analyzer battery fault

Depends, if the active components operate with a 3.3V rails, then check what the meter puts out on the resistance range, if it's over 3.3v, then yes it can do damage if you probe the wrong places.

If just doing voltage checks, as long as you don't short any pins together it should be fine.
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