[Kenwood] TS-940S Cooling Fan Problem

[John E.Cleeve]

----- Original Message ----- 
From: John E. Cleeve <g3jvc at jcleeve.idps.co.uk>
To: 'Bill Stewart' <bstewart at ipass.net>
Sent: Thu Oct 27 15:48
Subject: Fwd: Re: [Kenwood] TS-940S Cooling Fan Problem



Bill, get an old hypodermic syringe, or similar syringe, and use that 
to inject some very thin sewing machine oil into the fan bearings, 
this is a service recomendation, it applies to both fans on the 
TS940s....do not let that fan stop, or you will lose your TS940 PSU 
series regulator transistors, they go into thermal runaway, and then 
go short circuit, that will make the PA 28volt rail, rise to 40 volts, 
which will then destroy the PA board transistors before the internal 
fuse blows!!!!! A Pair of PA output transistors, cost me 167 pounds 
sterling, plus tax 17.5% UK sales tax, from Kenwood in Japan. I 
learned the costly way.... Now, I always keep a desk fan blowing 
across the back of my TS940, at all times, when the rig is in use, in 
case either the PSU fan or worse, the PA fan ever stops again.....take 
care, John.G3JVC.


On Thu Oct 27 14:25 , 'Bill Stewart' bstewart at ipass.net> sent:

>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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