Kenwood car amp power connections

[smackoj]

hi gents; I picked up a car amp listed as 'not working'. I have done visual and smell inspections, no burns. I believe the problem is not understanding the power connections. Could someone look at this diagram and tell me if I can run this without having a 12 vdc 'Center Control' device like a graphic eq or CD player?  I have a good regulated 12 vdc power supply.

thanks   

[sluckey]

Could someone look at this diagram and tell me if I can run this without having a 12 vdc 'Center Control' device like a graphic eq or CD player?

You will need some kind of signal source. This is just a couple power amps. Each power amp has an input sensitivity control to set depending on the output signal level of your source device. What do you plan to connect to it?

[shooter]

'Center Control'

Might even be able to use a guitar, if I read right you need 300mV, so hot pickups should do it, although I'd start like Sluckey said CD player, etal

[smackoj]

Sorry for the wrong idea with my explanation. I'm just trying to get the amp to power up. It's not coming 'on' with the 12 vdc plus and minus hooked up which I have tried. It appears that the 3rd power connection pole is to connect power from some type of device i.e. graphic eq or cd player etc. (I'm not sure if it pulls power or sends power) that lets/tells the amp to power up. I have been successful at getting some other car amps to power up by using a resistor from the 'Remote' connector to the plus pole. That didn't seem to work with this amp bur maybe I didn't have the right amount of resistance? It's a little confusing because most car amps label their 3rd pole on the power connectors as 'Remote'. Kenwood uses the term 'Power Control Terminal' and it's asking for a connection from the 'Power Control Lead' off of the eq or cd or other piece of equipment.

thanks,  jack d

[sluckey]

The power control terminal on your power amp is an input. A control voltage from your control device tells the power amp to turn on/off. Hard to say if that control terminal should be a positive voltage or a ground. Since you were unsuccessful using a positive voltage try connecting it to the ground terminal.

Probably a google search would tell you how to connect it.

[PRR]

The amp turns-on with a "power antenna" feed. Some fancy cars had whip antennas that retracted unless they got power from the radio (harder for the punks to bust-off, also sleeker in the driveway). Most trunk-amps use the same scheme so you do not need high-power switching. They want a fat permanent wire to battery, and the small "ANT" feed from the radio which enables them.

That's what the "power control lead" is. Goes hot when the head is turned on, but not intended to carry the many-many amperes of a trunk-amp.

Since this is not a whip-retracting motor, and very likely a transistor switch, first try a 1K resistor from +12V to "power control". If right, it will turn-on. If wrong, no smoke. However I am 99% sure you would just run a no-Ohm feed from 12V. Through radio/head in car, with clip-lead on the bench.

If you are on the bench, a large power-amp may not turn-on well with a small 12V supply. They use a switching buzzer to transform 12V to +/-40V. At turn-on this must charge-up some fair-size caps. A small 12V supply may collapse and foil the power converter. The safest bet is a tractor/cycle/ATV battery, backed-up with a charger for extended testing. Even this will not hold-up if you sine-test the full 320 Watts output, but should work for short very-loud music testing.

[smackoj]

Excellent; Yes, I am trying to bench test this amp. I have a pretty stout regulated power supply but I'm sure you're right that it won't stand up very long at 320 watts. I'll try to figure out something to control the volume while testing. Maybe I should get one of the big magnet sub woofer speakers and not put any music signal thru the amp, just listen for the obvious hiss? I don't have a signal generator. I will report back after further testing.

thanks,   

[sluckey]

While testing don't forget that it really may be a 'not working' unit. 

[smackoj]

After some pretty thorough testing, I cannot get it to power up. I used my current limiter and tried numerous ways of hooking up power including the 1k R from 12+ pole to the 'Power Cntrl' pole, I tried using the Neg. pole to the Pwr Cntrl pole, and eventually I tried a 2nd 12 vdc pwr source straight into the Pwr Cntrl post with only this to report;  In most cases the amp lights up the current limiter too bright and stays there without dimming down and hearing any speaker hiss (unlike some car amps this one doesn't have an on-off light on the chassis). When I tried the separate 12 vdc on the Pwr Ct post, the current limit bulb slowly flashes on then off again. Not what I want to see of course. I would try to bypass the 3 post Power Hookup panel but I'm not sure how to do that with the on-off being controlled by the low current 12 volts to the Pwr Cntrl connection. I hate to throw the amp out because it is made in Japan with quality parts and workmanship, but may have no other option. I'll give it another visual inspection and hope for the best.

 

[PRR]

Open it up, see what you see (or smell).

It likely is not made to be repaired, so don't struggle too hard.

Such amps are not terribly expensive. The cheapest Watts in the audio world. Performance is generally fault-free.

[sluckey]

Your current limiter (I'm assuming the lamp limiter we use for testing line operated amps) is totally wrong for a 12V DC device that wants 25 amps!

[smackoj]

"least expensive watts in the audio world"  yes indeed, that's why I like to attempt to make 'em work. cost is close to zilch.

Point well taken SL about the light bulb limiter. I'll try something different and see how it reacts.  thanks

[smackoj]

Finally powering up after getting the lamp bulb limiter out of the power supply. I do get music through the amp but it pulses on and off apprx. once per second. Don't know what that means but I'm probably not going any further to save it from the bone yard.

thanks amigos,   jack d

[PRR]

> wants 25 amps!

I figure over 40 Amperes for FULL power sine test.

Since it is sold for speech/music purposes, where average is far below peak (even at atrocious overload), 25A fuse is probably a dividing line between "working hard and OK" and "sick/shorted".

The *idle* current ought to be 10X lower. 2 to 4 Amperes. Maybe more. Especially with MOSFETs (I didn't notice).

Even so, 2-4A is a lot for a non-car bench supply. I'd really try it on the lawn-tractor battery.

These things have some smarts. If it turns-off constantly, it may have a good reason.

[smackoj]

I'll see if I can scare up a battery and give it a shot.  thanks

[smackoj]

I had to purchase a lawn tractor battery and still waiting for it to arrive. I will update when I get to run the amp on batt. power.

[shooter]

I had to purchase a lawn tractor battery

My wife's car was always a good place to find 12vdc

[smackoj]

Final notes about this Kenwood Japan car amp. Testing done with battery and no better results. I re=sold it at a 5 buck loss and put it on the bus to some other aspiring tech. I guess the wise old timer SL was spot on again, "sometimes a not=working amp really is not-working"  and some times the old ways are the good ways to quote my friend Jim Varney aka Ernest.

thanks to all who contributed to my continuing education.

jack