What's this "filter" on a Kenwood Car CD/Radio wire?

[Jeff Wisnia]

I'm helping the kid next door swap radios in his Honda Civic.

He's replacing the factory radio a Kenwood CD/radio someone gave him. He
purchased an adaptor connector and I took care of confirming the
connections and soldering/shrink tuping them for him. It works fine.

The Kenwood had what appeared to be some kind of "filter" in it's yellow
"memory power" lead.(NOT the "switched power" lead.) All the leads
appear to be hard wired to the radio, so this "filter", or whatever it
might be, looks like it must have been put there by the manufacturer.

It's a black plastic thing, about 7/8" square by 1-3/4" long and feels
heavy enough so that it may have an inductor in it. The "memory power"
lead goes in the center of one end and out the other end.

My curious mind wants to know whether this "filter" is likely to have
been put their by Kenwood, and why they had to hang it on the "memory
power" lead anyway.



Thanks guys,

Jeff


P.S. I'm not up on what today's car audio stuff looks like. I haven't
had much to do with that (other than listening to it) since my after
high school job in the early 50s, so Back then I worked for a "Car
Rasio" shop and spent a lot of time standing on my head cramming two
piece aftermarket tube radios under the dashboards of cars. In that era
radios were "optional extras" on most new cars and a lot of folks
declined buying the factory radios because they could have a AM radio
and antenna installed by a shop like the one I worked at for far less money.

--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"As long as there are exams in public schools there will be prayer in
public schools."

 

[Ken]

I'm helping the kid next door swap radios in his Honda Civic.

He's replacing the factory radio a Kenwood CD/radio someone gave him. He
purchased an adaptor connector and I took care of confirming the
connections and soldering/shrink tuping them for him. It works fine.

The Kenwood had what appeared to be some kind of "filter" in it's yellow
"memory power" lead.(NOT the "switched power" lead.) All the leads
appear to be hard wired to the radio, so this "filter", or whatever it
might be, looks like it must have been put there by the manufacturer.

It's a black plastic thing, about 7/8" square by 1-3/4" long and feels
heavy enough so that it may have an inductor in it. The "memory power"
lead goes in the center of one end and out the other end.

My curious mind wants to know whether this "filter" is likely to have
been put their by Kenwood, and why they had to hang it on the "memory
power" lead anyway.



Thanks guys,

Jeff


P.S. I'm not up on what today's car audio stuff looks like. I haven't
had much to do with that (other than listening to it) since my after
high school job in the early 50s, so Back then I worked for a "Car
Rasio" shop and spent a lot of time standing on my head cramming two
piece aftermarket tube radios under the dashboards of cars. In that era
radios were "optional extras" on most new cars and a lot of folks
declined buying the factory radios because they could have a AM radio
and antenna installed by a shop like the one I worked at for far less
money.

Could this be to keep the memory power clean while the car is being
started??? The impact of the starting a car on the battery voltage
might be enough to alter the memory settings without it. It might be a
diode for isolation and a capacitor for filtering???

 

[Jeff Wisnia]

Could this be to keep the memory power clean while the car is being
started??? The impact of the starting a car on the battery voltage
might be enough to alter the memory settings without it. It might be a
diode for isolation and a capacitor for filtering???

That's sort of along the lines of what I was thinking too, thanks.

Except, if there's a capacitor there, there's no return to ground for
it, so I don't see how it could do much good, huh? Perhaps its a diode
in series with a BMF inductor and the cap is inside the radio. That'd
take care of positive and negative spikes on the battery bus.

It may have been a "fix" Kenwood added after the original CD/Radio
design was frozen.

My curiosity wasn't great enough to make me crack the plastic case open,
or even to try and define it through one of those "black box" problems
we used to get in EE lab courses.

Jeff

--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"As long as there are exams in public schools there will be prayer in
public schools."

 

[Ken Weitzel]

That's sort of along the lines of what I was thinking too, thanks.

Except, if there's a capacitor there, there's no return to ground for
it, so I don't see how it could do much good, huh? Perhaps its a diode
in series with a BMF inductor and the cap is inside the radio. That'd
take care of positive and negative spikes on the battery bus.

It may have been a "fix" Kenwood added after the original CD/Radio
design was frozen.

My curiosity wasn't great enough to make me crack the plastic case open,
or even to try and define it through one of those "black box" problems
we used to get in EE lab courses.

Jeff

Hi Jeff...

Nothing more than a shot in the dark, but wonder if
it might not be an ordinary old electrolytic in a
unique case?

The theory there would be that it would charge up
to (about) 12 volts... and hold it for a few minutes,
so that changing a battery or cleaning the contacts or
whatever would be possible without losing the radios
memory?

Take care.

Ken

 

[Ampdoc]

It's an inductor. There is usually a 1600Uf 16WV electrolytic inside the
head unit, some products had the capacitor in the black box, but those had a
ground lead on the box. The yellow wire also supplies power directly to the
audio output and regulators. The inductor is there both to keep noise from
the car from reaching the output, and to keep RF emissions from the radio
from the car's system so the engine computer doesn't have problems. Most
mfr's have one, some place it inside the radio, but on higher end product
where board real estate is at a premium they place the inductor in the power
lead. The turn-on lead (red wire) doesn't need it (an inductor) as it is ran
through a circuit which grounds the PON (Power ON) input at the unit's
micro.


--
Jammy Harbin
J & J Electronics, Inc.
227 S. 4th St.
Selmer, TN 38375
731-645-3311

 

[Jeff Wisnia]

It's an inductor. There is usually a 1600Uf 16WV electrolytic inside the
head unit, some products had the capacitor in the black box, but those had a
ground lead on the box. The yellow wire also supplies power directly to the
audio output and regulators. The inductor is there both to keep noise from
the car from reaching the output, and to keep RF emissions from the radio
from the car's system so the engine computer doesn't have problems. Most
mfr's have one, some place it inside the radio, but on higher end product
where board real estate is at a premium they place the inductor in the power
lead. The turn-on lead (red wire) doesn't need it (an inductor) as it is ran
through a circuit which grounds the PON (Power ON) input at the unit's
micro.

Thanks, I should have picked up on that because the yellow lead (the one
I called "memory power") was a size or two heavier than the red
"switched power" lead.

In defense of my oversight, the original Honda factory Tape/radio the
kid pulled out of his car was playing OK, but not "remembering" anything
because the fuse powering the yellow lead was blown. So, I had a brain
fart and just assumed that the yellow wire only kept the memory awake,
and the red wire was the one "that counted".

I guess I'm guilty of still having my brain stuck back in the pre-hybrid
audio amp, pre-ASICs for everything, and yes, even the pre-"ruin your
hearing" car audio daze. I didn't even think about a "power down" scheme
for the radio circuits controlled by the red lead.

The audiologists must love what the kids are doing to their ears with
that stuff.

Jeff

 

[LASERandDVDfan]

The audiologists must love what the kids are doing to their ears with

that stuff.

Fortunately, bass that you feel doesn't hurt your hearing.

However, a boost in volume means louder noise, not just bass.

"What's that you're saying?" - Reinhart