398-No Problem?

398-No Problem?

Post by Rick W 9 » Mon, 23 Mar 1998 04:00:00

Is it possible that a higher than normal voltage in my area could be causing my
problem? (Interference scrambling sideband signal)
I measured the voltage off my old un-regulated adapter and it was
8.04 volts. The new "regulated" adapter measures at 6.50 volts and does not
create interference on the sidebands. What is the maximum allowable voltage?
I'm thinking that maybe the AC is to high in my area and causes the
"un-regulated" adapter to pass along more voltage, thus screwing up the
sideband on the radio. I have been trying to find a bad ripple cap inside the
radio. Maybe the 398 doesn't have an internal ripple filter cap. and doesn't
expect such a high voltage at the ac adapter jack. Thanks for listening.
Any thoughts on this?
Rick

 
 
 

398-No Problem?

Post by Jim Bowli » Mon, 23 Mar 1998 04:00:00


This is possible but I think it is very unlikely.  You really need to test
the voltage output of the unregulated adapter under load.  Either look at
the voltages inside your radio with the adapter pluged in or create a
dummy load.  The adapter is rated for 300 mA at 6 volts.  This calls
a 20 Ohm load resistor.  But be careful.  That resistor will be disapating
almost 2 Watts.  On the other hand, they rate battery life using a typical
power consumption of 50 mW.  This corresponds to a (roughly) 600 Ohm load
resistor.  So I would suggest measuring the output of the adapter when it
has a 600 Ohm resistor across its output.  You may want to add a capacitor
as well.  500 uF would work.   But I really don't think that this is your
problem.

-- Jim Bowlin


> Is it possible that a higher than normal voltage in my area could be causing my
> problem? (Interference scrambling sideband signal)
> I measured the voltage off my old un-regulated adapter and it was
> 8.04 volts. The new "regulated" adapter measures at 6.50 volts and does not
> create interference on the sidebands. What is the maximum allowable voltage?
> I'm thinking that maybe the AC is to high in my area and causes the
> "un-regulated" adapter to pass along more voltage, thus screwing up the
> sideband on the radio. I have been trying to find a bad ripple cap inside the
> radio. Maybe the 398 doesn't have an internal ripple filter cap. and doesn't
> expect such a high voltage at the ac adapter jack. Thanks for listening.
> Any thoughts on this?
> Rick

 
 
 

398-No Problem?

Post by Rick W 9 » Mon, 23 Mar 1998 04:00:00

Yes, not likely.
Rick

 
 
 

398-No Problem?

Post by Jerry Bianch » Mon, 23 Mar 1998 04:00:00


> Is it possible that a higher than normal voltage in my area could be causing my
> problem? (Interference scrambling sideband signal)
> I measured the voltage off my old un-regulated adapter and it was
> 8.04 volts. The new "regulated" adapter measures at 6.50 volts and does not
> create interference on the sidebands. What is the maximum allowable voltage?
> I'm thinking that maybe the AC is to high in my area and causes the
> "un-regulated" adapter to pass along more voltage, thus screwing up the
> sideband on the radio. I have been trying to find a bad ripple cap inside the
> radio. Maybe the 398 doesn't have an internal ripple filter cap. and doesn't
> expect such a high voltage at the ac adapter jack. Thanks for listening.
> Any thoughts on this?
> Rick

Unregulated Adapters are just that.  Notice that they are rated at a
specific voltage and current.  If you try to measure the voltage without
the rated load, the voltage will be high.  The voltage is not your
problem, it's the filtering.  Most regulated supplies have both a
voltage regulator to maintain a constant voltage along with filter
capacitors to smooth out the ripples.

If noise is a problem, get a regulated supply or filter the old Wall
Wart, but placing a cap on the output.  Start small and increase until
the hum is acceptable.  Too much capacitance will load the unit.

Good Luck

Jerry B

 
 
 

398-No Problem?

Post by CW » Tue, 24 Mar 1998 04:00:00

When checked with a voltmeter an unregulated power supply will always read

will deliver 6.5 volts when connected to a load that draws 250 ma. If the
device draws less current ( such as your voltmeter ) the voltage will be
higher.It also works the other way around, more current draw, lower
voltage. When using an unregulated supply, get one that is rated for the
voltage and current that the radio is rated at. The regulated supply keeps
the voltage constant regardless of current  draw up to the rated capacity
of the supply. The reason you have no interference problems when using the
regulated supply is that regulated supplies are made with more criticle
applications in mind, consequently the are filtered better.
--
CW
KC7NOD



Quote:> Is it possible that a higher than normal voltage in my area could be
causing my
> problem? (Interference scrambling sideband signal)
> I measured the voltage off my old un-regulated adapter and it was
> 8.04 volts. The new "regulated" adapter measures at 6.50 volts and does
not
> create interference on the sidebands. What is the maximum allowable
voltage?
> I'm thinking that maybe the AC is to high in my area and causes the
> "un-regulated" adapter to pass along more voltage, thus screwing up the
> sideband on the radio. I have been trying to find a bad ripple cap inside
the
> radio. Maybe the 398 doesn't have an internal ripple filter cap. and
doesn't
> expect such a high voltage at the ac adapter jack. Thanks for listening.
> Any thoughts on this?
> Rick

 
 
 

398-No Problem?

Post by Rick W 9 » Tue, 24 Mar 1998 04:00:00

I just discovered something. You know that when you have the 398 running off
the adapter and you un-plug the adapter and the radio starts to run off the
batteries? Well mine doesn't do that anymore. Now when I unplug the adapter, it
shuts off and says low battery. If the adaper plug is in the jack and there is
batteries in the radio, it won't power up with the batteries. You have to
un-plug the adapter from the side of the radio before it will run off the
batteries. Does that sound like a bad cap?
Rick

 
 
 

398-No Problem?

Post by Sky Kin » Tue, 24 Mar 1998 04:00:00

Rick,

I don't think you're going to find a ripple cap in the radio. The radio
mfg usually relies on the adapter to provide smooth DC and does not design
in additional filtration in an effort to keep production costs down.
Anybody out there in the news group able to givi a better explanation on
'ground loop effect' than I can? This is sounding more and more like the
radio is using the ac line to provide a ground, with hash on the line
getting into the signal. The regulated adapter provides a bit more
isolation from the ac line than the unregulated one.. :)

I have one outlet in my house that gives me a ton of hum on my portables,
and they all use different adapters. *laughs* yYa know, the hum actually
gets worse when I turn on a certain incandescent light... Go figure!

I hope you can get to the bottom of your problem, Rick!

Ken

 
 
 

398-No Problem?

Post by Howard N. Lu » Tue, 24 Mar 1998 04:00:00



Quote:>>>Is it possible that a higher than normal voltage in my area could be causing my
>>>problem? (Interference scrambling sideband signal)
>>>I measured the voltage off my old un-regulated adapter and it was
>>>8.04 volts. The new "regulated" adapter measures at 6.50 volts and does not
>>>create interference on the sidebands. What is the maximum allowable voltage?
>>>I'm thinking that maybe the AC is to high in my area and causes the
>>>"un-regulated" adapter to pass along more voltage, thus screwing up the
>>>sideband on the radio. I have been trying to find a bad ripple cap inside the
>>>radio. Maybe the 398 doesn't have an internal ripple filter cap. and doesn't
>>>expect such a high voltage at the ac adapter jack. Thanks for listening.
>>>Any thoughts on this?
>>>Rick

Hi Rick,
You're on the right track tho' if you measured the voltage "no load" the
readings will be abnormally high on some types of Ps's. The radio DOES
have internal filter(s) BUT they cannot/will not filter completely out-
of-range AC on the DC line IN. I would do the following to insure the
quality of any "wall-wart"...split the leads, place a 500-1000mfd 16v
electrolytic cap across them before using it on the YB...or any other
portable for that matter.
friend,
Lute

--
Howard N. Lute,
aka. "Lute"
Electronics Instructor, Terrible Mechanic, Worse Plumber