Hum from Pro 163?

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pkivolowitz

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Hi,

I have a new Pro 163 and it has an awful hum. The frequency of the hum changes with the intensity of the backlight (hitting DIM changes the frequency of the hum). It is impossible to use headphones as the hum is too annoying. It doesn't seem to be a grounding problem or interference from a computer.

I have a 164 (portable) with absolutely no hum at all.

Should I bring this 163 back to RS?
 

Bucko

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Most likely your AC adapter that powers your PRO 163, the Power supplies in Wal Warts are not that good sometimes. No need to return the radio, just the adapter.
 

DickH

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Hi,

I have a new Pro 163 and it has an awful hum. The frequency of the hum changes with the intensity of the backlight (hitting DIM changes the frequency of the hum). It is impossible to use headphones as the hum is too annoying. It doesn't seem to be a grounding problem or interference from a computer.

I have a 164 (portable) with absolutely no hum at all.

Should I bring this 163 back to RS?
Did the hum start at the same time as your other problem?
YES, send it in for repair.
 

pkivolowitz

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Hi Dick,

These are two different devices. I purchased a desktop and portable. Both were display units. The desktop (with the hum) came with an alternate brick as the RS folks had lost the brick that came with the unit. The alternative brick is 12V, while the unit is labeled as needing 13.8V. I figured this was OK as the unit can also be car mounted (which I assumed would be 12V).

I really appreciate the responses.
 

DickH

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Hi Dick,

These are two different devices. I purchased a desktop and portable. Both were display units. The desktop (with the hum) came with an alternate brick as the RS folks had lost the brick that came with the unit. The alternative brick is 12V, while the unit is labeled as needing 13.8V. I figured this was OK as the unit can also be car mounted (which I assumed would be 12V).

I really appreciate the responses.
Just sent you a Private Message.
 

nanZor

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These are two different devices. I purchased a desktop and portable. Both were display units. The desktop (with the hum) came with an alternate brick as the RS folks had lost the brick that came with the unit. The alternative brick is 12V, while the unit is labeled as needing 13.8V. I figured this was OK as the unit can also be car mounted (which I assumed would be 12V).
I've been there with display units and they try to throw in an adapter that is not even applicable - all they see is "12V" and think it is good. :)

I'd try an adapter that meets the specs of the radio first. (they have tried to pawn off 12V AC adapters which definitely will cause hum problems), OR they throw in adapters that don't meet the current requirements - sure it's 12V DC at 100ma, but the radio really requires a 500ma current spec. Check the manual to make sure that the wall-wart you need will meet the specs for voltage, DC, and current in milliamps.

Other freebies thrown my way have been CB-type rubber ducks. Not applicable. :)
 

DickH

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Definitely need the 13.8 supply. !2 volt on household current will run it, but just will not provide what it needs to run correctly.That is what is causing the hum.
The voltage of a power supply has nothing to do with hum. The hum is caused by not enough filtering.
 

N8IAA

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If the AC adapter is not providing at least 800ma's, which is the required amount for the radio, it will cause the radio to 'hum'. I would take back the adapter with the manual, and make sure they get you the proper one. Another way to check this, is to use the DC adapter that came with the radio and hook it into your car or a 13.8v power supply. Another consideration, is the fact that it was a display radio. I will shortly be be putting my 163 on a 13.8v DC power supply. The radio will draw the current it needs to operate efficiently and much cooler:)
HTH,
Larry
 

Benzman66

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The voltage of a power supply has nothing to do with hum. The hum is caused by not enough filtering.
Gee, I can't be too wrong if others agree with my viewpoint, or maybe we are all nuts except Dick?
Granted, if the hum is existing when using batteries and NO AC cord attached, then it is another problem, but I know from my own experiences that using a lower powered adapter will cause a hum. Just tried two different adapters again on my one scanner to make sure I wasn't nuts.

If the AC adapter is not providing at least 800ma's, which is the required amount for the radio, it will cause the radio to 'hum'.
I'd try an adapter that meets the specs of the radio first. (they have tried to pawn off 12V AC adapters which definitely will cause hum problems)
Sure fixed my issues quite a few times by using the right adapter, and not just with scanners, but all electronics!
 
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Evert

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Gee, I can't be too wrong if others agree with my viewpoint, or maybe we are all nuts except Dick?
Well, according to that logic, Dick can’t be too wrong either because I agree with him.

……. I know from my own experiences that using a lower powered adapter will cause a hum. Just tried two different adapters again on my one scanner to make sure I wasn't nuts.

Sure fixed my issues quite a few times by using the right adapter, and not just with scanners, but all electronics!
The “lower powered” adapters probably are smaller in physical size and have smaller or no filter/bypass capacitors.

Using a power supply with a current rating less than required by the scanner will cause the power supply to over heat and possibly catch on fire. (It will die trying.)

…… I will shortly be be putting my 163 on a 13.8v DC power supply. The radio will draw the current it needs to operate efficiently and much cooler:)
HTH,
Larry
Power dissipated inside the scanner is voltage times current. Please explain how having a higher voltage and higher current input would make anything run cooler.

The 13.8 volt rating is so that the charging voltage of vehicles will not damage the scanner. The scanner will work with no problem even if the vehicle battery has discharged to less that 12 volts. Since most of the internal circuits operate at voltages much less than 12 volts, the input goes through voltage regulator circuits and more heat will be generated when “throttling down” from 13.8 volts than when throttling down from 12 volts.

The internal circuits(other than the voltage regulator circiuts) will operate at exactly the same level of efficiency and quality when the input voltage is 12 volts as they would if the input voltage is 13.8 volts.

……. It is impossible to use headphones as the hum is too annoying. It doesn't seem to be a grounding problem or interference from a computer.
The earphone connector on the front of these scanners connects the sleeve to ground via a resistor and makes the effects of a poorly filtered power supply worse. You will get a lot less hum from your poorly filtered power supply if you plug the earphone into the speaker jack at the rear of the scanner. You have to be very careful doing this though because the volume in the earphones will be a lot higher at a particular setting of the volume control.
 
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DickH

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Well, according to that logic, Dick can’t be too wrong either because I agree with him.

The “lower powered” adapters probably are smaller in physical size and have smaller or no filter/bypass capacitors.

Using a power supply with a current rating less than required by the scanner will cause the power supply to over heat and possibly catch on fire. (It will die trying.) QUOTE]

Well Evert, you have obviously have had some education and know what you are talking about.
Back in the 50's we had guys who tried to diagnose and fix their own radios (long before scanners), and we used to say, "They know just enough to be dangerous." :) :)
 

Evert

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...... Well Evert, you have obviously have had some education .....

....Back in the 50's ......we used to say, "They know just enough to be dangerous
Back in the 50s I was a crew chief on a F-84F and when my bird had radio problems I would sic the radio guys on it. ;)

Since then I took several EE courses while I was working toward my mechanical engineering degrees. I have always liked things electrical/electronic and have been a ham for about 35 years during which time I built and used a number of transmitters, receivers, and test equipment.

But I do not consider myself as being an expert electronic person – just know enough to be REALLY dangerous. :)
 
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