[Icom] IC-910H heat/fan problem

[Jens Schmidt]

Hi Ron,

I can confirm you have a problem / abnormal operation.
Mine will start the fan at TX start, low speed,
if TX is on for short duration, and fan speed does not increase
fan will stop with TX stop.
If TX continues and heat builds up, then fan speeds up to
second stage, on TX stop fan reduces to first stage speed
and continues a while.
If TX is lengthy with high power then the fan will go from
first stage, through second stage to third stage (loud),
and on TX stop reduce to second stage and continue a while.

I have not had the 910H beyond this, but seem to remember
that the 471H had a fourth stage, where the fan was on high
speed and the TX LED started flashing along with reduced
power out.
(Fifth stage was replacing Finals and sometimes rebuild PSU -:( .)

Good luck, or better, good servicing.

73 Jens    ZL2TJT

p.s. Had lots of trouble with that circuitry on the 471H,
sensitive to internal characteristic's of replacement fan too!

Ron Tivey wrote:

> Hello to all,
>
>         I have a IC-910H with all the option installed.  I haven't had any
> problems till today.  My wife being long winded was talking to a friend
> for several minutes in 2M FM about 40W when the radio cycled off and on
> when she keyed up.  I repeated this when I ran the radio on a dummy load
> for a while.  The problem appears to be heat.  When the radio is
> transmitting the fan will cycle from slow to fast until the PTT is
> released.  Then the fan stops.  Seems to be ambient temp build-up during
> tx/rx cycles.  Shouldn't the radio fan stay running until the temp drops
> below a set point from a thermostat?  I never noticed this before so I
> don't know it this is a problem with just my radio or a design problem.
> Anyone out there with an answer?  I don't what to send this radio to
> ICOM only for them to say it's okay.  I would appreciate if someone with
> a IC-910H could duplicate this test and forward a result to me.
>
>                                 Ron, N4GFO
> ----
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