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-   -   Audiobahn A8002T fan (http://www.diyaudio.com/forums/car-audio/45222-audiobahn-a8002t-fan.html)

Regal1 8th November 2004 07:36 AM

Audiobahn A8002T fan
 
Just installed this amp, and it hits super hard powering 2 12" Alpine Type R's in my Wrangler, after an hour drive last night, it cut off and was hot. I turned it down for about 3 minutes and it came back on. after I got home, I took the cover off and powered it up (smelled hot electronics when it shut down) and the fan does not turn, 0V at the fan plug when the amp is powered up. My question is, is this fan temperature controlled, or should it be on all the time?

Thanks!

mattjk 9th November 2004 07:53 AM

I have the 4ch version, and it stays on all the time.

I don't have it in my car however. It has been sitting in my bedroom for over 6 months... I got bored and hooked it up to my home stereo. It consists of Acoustat 2+2 speakers, Pass Labs X2.5 preamp, and a ZAPpulse digital amp.

Wow, the Audiobahn amp sounds pretty damn good. Very detailed, super smooth, and good soundstaging. The bass is a bit soft, but I am using a weak battery right now -- one of the jump start boxes. It sounds WAY better than the ZAPpulse. :confused:

sdoom 9th November 2004 10:44 AM

Usually car amplifiers equipped with a fan turn on the fan when the unit is powered on. Exceptions are Kenwood KAC-x23 series, they have a regulated fan. I had a 823, 923 and 2 1023 but their fans never turned on :)

but you can check that easily. The fan is always connected to a small power-transistor . you can find the transistor by following the lanes on the curcuit board. If you find the switching transistor you can check itīs base connection. usually that goes to a resistor that is connected to the remote-terminal.

probably the transistor is burned.

Regal1 9th November 2004 06:42 PM

Thanks alot for your replies, I figured it was supposed to be on all the time, the fan isnt burned out, i have tested it with my power supply. There is also 0volts at the plug where the fan connects, i will check the transistor and let you all know what i have found.

Thanks again.

Regal1 16th November 2004 02:55 AM

Alright, the culprit seemed to be, so far, a visible cold solder joint at the fan plug on the bottom of the board. the transistors check out, now there is 12v at the plug, and when the amp is turned on, the fan jumps 1/4 turn, but doesnt seem to spin up. The fan works by itself on a 12v source, and with the fan load in the loop, there is still 12v at the plug, I'm lost. Any suggestions?

sdoom 16th November 2004 10:45 AM

does it turn by itself once you push the fan by hand ?

Regal1 16th November 2004 08:30 PM

no it does not, it just stops. Does anyone know if there is a current limiting circuit that contols the fan?

sdoom 16th November 2004 11:31 PM

usually not. Most amplifiers turn on the fan with a remote-signal follower. Thatīs a small power transistor and a resistor that connects the transistorīs base to the remote - terminal , just like all illumination curcuits do if the amp is equipped with that.

If there is a real RPM-control curcuit , you will also find a transistor that powers the fan. But then the base is not connected (via a resistor) to the remote - terminal . It can be an easy threshold - curcuit ore a more complex current- limiter.

Can you make a picture (front and back) of the curcuitboard of that area where the fan is connected ?

Regal1 18th November 2004 01:51 AM

I haven't yet had a chance to take the amp apart again for pictures. But i can tell you this, the fan motor, though not spinning, is getting extremely hot after it's powered up for about 15 minutes or so. Any ideas on this?

sdoom 18th November 2004 02:13 AM

Hm, this is really strange . If it gets hot, it gets power.

Did you mount the fan to the heatsink/chassis ? Maybe the fan itself doesnīt rotate if it is bended or smthg. Usually the fans installed in car amps are not really high quality parts. So if it is "physically stressed" the bearing inside will block free rotating .

Do you have access to a scope ? With a scope you could see how the voltage really looks. Maybe there is a control /regulating curcuit that causes the trouble and it is sending pulsed signals by fault (instead of a normal 12V DC voltage) ..... a normal DC-voltmeter will only show the RMS - value, thatīs why maybe you read 12V but the fan doesnīt spin.......

I doubt that there are complex kind of curcuits installed. I have fixed a lot of car amplifiers so far and some of them had fan controls , but they all have been rather simple applications. Actually the "tuffest" curcuit had been a double fan layout where #1 fan was turned on with the RMT-signal and #2 fan was turned on by a NTC-resistor.


greets from Germany

sdoom


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