Kenwood Stereo in 5KCS problem

[Steve Sherman]

Ameer:

50ma is what I measured as the cuurent coming out of the power antenna lead,
when connected to the two wires that the Bose radio powered when on (believe
one goes to the rear amp and the other to the antenna amp).  I agree with you,
that 50ma is not enough to power much of an amp.  But most amps, at least after
market ones, have an on/off lead that is intended to connect to the likes of a
power antenna lead.  They draw little current on this on/off lead and use it
primarily as a switch input.  I've been assuming that was what is going on
here.  Certainly possible that the meter is off, I will try another.

What I mean by the unit will come up is just what I had found.  In my
experimenting, I found that if I connect the leads for the rear speakers after
the radio/tape unit was up and playing thru the front speakers (making sound),
then the rear speakers would work too; eg sound out of all 4 speakers.
(Although as I mentioned in my previous post there was sufficient current draw
on the leads to the rear amp from the tape unit to heat a series resistor).  If
the rear speaker leads were tied to the rear amp before powering the unit up,
no sound out of any speaker.

My current guess is that the Bose rear amp takes a input signal to ground
without any series cap in the circuit.  If that were the case, then it could
draw considerable DC current (enough to warm the resistor as I found).  I am
planning to experiment some more and will post what I find, just in case anyone
else out ther is trying to use the Bose amp...



Ameer Antar wrote:

> 50mA is not even close to what is needed for an amplifier. Believe me, no
> antenna lead is gonna run an amplifier, well maybe a 1/2W headphone amp!
> Unless the rear amps aren't really amps (maybe crossovers), they'd probably
> need at least 3-5 amps each. What do you mean by: "but since the unit will
> come up with sound playing with the rear amp lead connected to the antenna
> lead but the rear speaker connections cut.."? Where is the sound coming
> from, the fronts only? Well that makes sense. When you connect the speaker
> load to the rear amps, they will cut out as they can't run such a load off
> of 50mA. I'm not sure what you were trying to do w/ the resistor, but I
> guarantee you  can get the whole system working by connecting the 4 Kenwood
> speaker wire ouputs directly to the speakers. If you have separate woofers
> and tweeters, it's ok to test on the woofer only first. For permanent
> design, all you need is a simple coil and cap for each as a crossover to
> separate the high and low frequencies. I wouldn't use chassis ground for
> any speakers and I'd avoid it for high power amps, b/c steel is not the
> best conductor, especially w/ all kinds of coatings like paint and zinc on
> it. Connect everything directly. There is no A.C. power in the car, except
> inside the alternator, but even that's converted to DC all inside the
> alternator. Another test just to see more possibilities, is to just run a
> wire from a 12V supply (battery or there are 12V connections in the
> driver's fuse panel) directly to the amps. Just try one. I guarantee this
> will keep the amp on, unless there's something up w/ the amp or the wiring.
> good luck.
>
> -ameer
>
> At 12:41 PM 7/7/2002, Steve Sherman wrote:
> >Thanks Ameer:
> >
> >I did check (best I could with a cheap digital multimeter) and the
> >current out of the antenna lead stabalizes at ~50ma.  Which I though
> >should be OK.  You may have something in that this meter is too slow to
> >register an inrush current, but since the unit will come up with sound
> >playing with the rear amp lead connected to the antenna lead but the
> >rear speaker connections cut, I tend to think it is something else.
> >
> >One other thing I tried, was to connect the + lead of the rear speakers
> >to the Kenwood through various resistors (from my junk box collection).
> >An odd thing was that even with a 50ohm resistor in series with the rear
> >speaker (to rear amp) lead, the problem did not go away, AND the
> >resistor got very WARM (this was a 1 watt resistor).
> >
> >This leads me to think that the excessive current draw is happening from
> >the kenwood to the rear amp inputs.  I'm not an EE, but it would seem
> >that the BOSE rear amp's inputs are sucking current. Probably need a
> >scope or the like to see if the excessive current draw is DC or AC.  All
> >the more odd in that only one line per channel is being connected (as
> >per archive post).  So the ground/return current path would seem to be
> >to chassis ground...  Perhaps the rear amp uses chassis ground for one
> >signal line, and thus shorts out the Kenwood amp, as one is not supposed
> >to introduce a chassis ground into the speaker wiring.
> >
> >Any thoughts on this?  Do any listers know what the correct input
> >impedance of the factory rear amp is and what a "good" mathching
> >transformer/cap would be?
> >
> >TIA