Randall, Randy wrote:
> That was a stupid design. Did the blower use two windings or two caps to
> change the speed or just a resistor? In the resistor type just shorting out
> the resistor would provide the same functionality AND provide a fail safe
> mode. If the switch failed at least the fan would be providing air to the
> system. K.I.S.S. is the way to go here.
>
> Randy AB9GO
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Bill Coleman
> Sent: Tuesday, September 08, 2009 10:30 AM
> To: Carl
> Cc: David J Windisch; amps@contesting.com
> Subject: Re: [Amps] 3CX800 and blower
>
> Carl wrote:
>
>> Yes, according to the Eimac spec sheet.
>>
>> It also sounds like a good reason to install a 2 speed switch as is in a few
>> commercial amps with that tube.
>>
>> It can be as elaborate as a thermal switch that runs the blower full speed
>> when necessary, to a simple toggle switch and a resistor.
>>
>> Carl
>> KM1H
>>
>> ----- Original Message -----
>> From: "David J Windisch" <davidjw@cinci.rr.com>
>> To: <amps@contesting.com>
>> Sent: Monday, September 07, 2009 10:26 AM
>> Subject: [Amps] 3CX800 and blower
>>
>>
>>
>>
>>> Does a 3CX800A7 require airflow any time the filament is lit, like, say,
>>> 3-500Z glass tubes with tender seals and 70-watt filaments?
>>>
>>> I'm thinking of leaving the (unobtanium) blower turned off, to lower wear
>>> and tear, until I need the power.
>>>
>>> Yep, I'm aware of the potential hazard of a senior moment: I have in mind
>>> a no-blower-no-operate interlock scheme.
>>>
>>> Tia & brgds,
>>> Dave, W8FGX
>>> _______________________________________________
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>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
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>>
>>
>>
>>
> A quick story regarding a 2-speed switch... I had a 1st generation
> TenTec Titan (pair of 3CX800s), its 2-speed fan switch is located on the
> power supply. I regularly operate wearing headphones & one day was
> running RTTY. I set the switch to high speed with my toe as the power
> supply was on the floor under the op table. A while later after many
> contacts I went to change bands, grabbed the bandswitch on the Titan to
> find it extremely hot, the case of the RF deck was too hot to touch.
> Yep, mid-way on the HI/LO fan switch was NO fan.
>
> This never happened again as I wired around the switch to force high
> speed all the time. I was very lucky, the amp is still around and the
> tubes still going after 20+ years.
>
> I still wear headphones all the time because my present amps make lots
> of noise but both are protected by air flow switches. The switch in
> one is a simple microswitch with a long actuating arm & a brass vane. No
> big deal to fabricate.
>
> I'm not a 'fan' of two-speed fan switches!
>
> 73, Bill N2BC
>
>
>
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>
Cheesy rocker style switch that would easily sit mid-throw.... OFF!
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