[Kenwood] TS-940S Cooling Fan Problem

[Garey Barrell]

Bill -

The problem is that the motor is drawing too much current at start-up.  
The supply voltage is applied through a series resistor and the excess 
current drawn because of the gummed up bearings is high enough to drop 
the supply voltage too low to start.  The correct fix is to replace the 
motor.  East Coast Parts has them but they are expensive, ~$30.   You 
might be able to find a hobby motor that will fit, if you look long enough.

A "temporary" fix is to put an 18V Zener diode across the motor dropping 
resistor so that if the voltage drop across the resistor is more than 
18V, the Zener conducts, supplying enough voltage to start the motor.  
Once the motor starts, the voltage across the resistor drops below 18V 
and the Zener is out of the circuit.  BUT this is only a temporary fix!  
If the motor freezes up, the 940 WILL overheat significantly.

73, Garey K4OAH
Chicago


Bill Stewart wrote:

>I have a TS-940S, s/n 6040XXX, which has a sluggish cooling fan (on left, facing front, behind the power trans.). Sometimes it will not start. I have shot WD-40 in it and tried to get oil to go down the shaft but sometimes it still won't start and if it does start, it turns slowly & erratically. I measured the voltage to be around 18VDC with the fan disconnected and connected, a fluctuating .5 to 1.5VDC with the erratic rotation.
>Questions: 1. Is this no-load to load voltage drop normal?
>                 2. Does the voltage and fan speed increase with temp. rise?
>                 3. If the above is a problem, are there any mods. to replace this fan or maybe make the fan run all the time?
>The fan runs ok if it gets beyond the low start-up point (on a seperate DC supply).
>Any comments will be appreciated, thanks...Bill K4JYS
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