[Amps] Cooling 77SX

[ros]

Just use a triac and a pot. and you have have a variable speed fan.


Ros




On 5/6/2016 5:18 PM, MU 4CX250B wrote:
> Hi Gary,
> The 77D and 77SX use a lovely mil spec Rotron blower. I've used the
> same model blower in a homebrew 8877 amp for thirty years and would
> love to find another one. Unfortunately, the blower uses an AC
> induction motor, and there's no easy way to adjust the blower speed. I
> use a 24 VAC transformer to reduce the AC voltage to my blower, and it
> kind of works but not very well.  A series resistor won't work because
> it can lead to startup problems and motor overheating, without
> affecting the motor rpm.
>
> 73,
> Jim w8zr
>
> Sent from my iPhone
>
>> On May 6, 2016, at 2:48 PM, Gary Smith <Gary at ka1j.com> wrote:
>>
>> As it sits now, the fan is always on at
>> the maximum amount and other than when I'm
>> on RTTY, the air temp from the exhaust
>> rarely gets over 110 degrees.
>>
>> The fan is noisy from the air turbulence,
>> the motor/bearings are as new. I would
>> like to reduce the fan to a low speed and
>> kick in at a higher temperature. What
>> would be ideal would be for the fan to
>> progressively increase the RPM to match
>> the cooling need and increase as the
>> temperature increases.
>>
>> Perhaps the most reasonable solution would
>> be to have the fan run at a minimum speed,
>> place a thermostat with probe in line and
>> have it kick in at one specific temp and
>> give full RPM at that point but I would
>> prefer a progressive speed:temp solution.
>>
>> I've also thought another option might be
>> to remove the fan & disconnecting the
>> power to the motor, connecting a 20' long
>> 6" duct to the exhaust vent and at the
>> distal end of the duct, have an in-line
>> fan.
>>
>> I can't visualize how to make a
>> progressive speed solution and I'm not
>> sure of a cost effective thermostat that
>> would be small enough to be internal to
>> the amp.
>>
>> Any suggestions, thoughts? I really would
>> like to keep the fan noise down in this
>> otherwise silent shack.
>>
>> 73,
>>
>> Gary
>> KA1J
>>
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