[Amps] Alpha vs Henry

[Paul Christensen]

I've never run into any 160m toroid heating issues with my 70V.  It's runs 
approximately the same class of service as the 77.  However, I did have a an 
RF arc issue that required placing the toroids about a quarter-inch away 
from the mounting surface.

I've never used the AL-1500 but have seen the inside components countless 
times at various hamfests.  Given the marginal quality of many RF 
components, its a testament to the overall design of the AL-1500 since I 
believe few have operation issues.  Still, it pains me to see Airdux coils, 
small ceramic band-switch wafers, sheet metal construction, weak mechanical 
anode cap, low industrial-grade blower, etc.

Paul, W9AC

----- Original Message ----- 
From: "Jim Barber" <audioguy at q.com>
Cc: <amps at contesting.com>
Sent: Wednesday, April 06, 2011 6:33 PM
Subject: Re: [Amps] Alpha vs Henry


> Interesting side-thread. I've been thinking about replacing my
> black-faced Alpha 77 with an AL-1500, primarily because the Alpha
> doesn't have 160 and I don't like the nature of the "upgrade" to put it
> in. (My "yellow-faced" PA77 has the 160 mod but I'm afraid to run RTTY
> or even full-power AM because I'm paranoid about the toroids)
>
> 73,
> Jim N7CXI
>
> On 4/6/2011 3:22 PM, Roger (sub1) wrote:
>> On 4/6/2011 5:05 PM, Al Kozakiewicz wrote:
>>> Can anyone tell me how much power an AL-1500 is rated to produce at a 
>>> 100% duty cycle?
>>>
>>> During RTTY contests and outputting about 1000 watts, the tube side of 
>>> the cabinet gets mighty warm.
>>
>> It should.  Running 100% duty cycle and 1500 watts out at 60% efficiency
>> means you are dissipating 1000 watts.  That is a LOT of heat. The temp
>> of the exhaust air depends on how much air (CFM @ however many inches of
>> H20) the fan can push.  The 8877 is a relatively small tube for its
>> ratings, but it has a fairly efficient radiator.  OTOH that means a
>> blower that can produce a fair amount of back pressure is required to
>> get full output from the tube.
>>
>> As a comparison, when I had an all electric house I heated the basement
>> and ham shack with 4400 watt space heaters mounted in the walls.  In the
>> dead of winter it only took a few minutes to heat the 13 X 21' den to
>> about 70 degrees. After that the heater would only kick on a few times
>> for only a few minutes per hour. That means your amp running under these
>> conditions puts out enough heat to require opening the den door to keep
>> a reasonable temp.  IOW you could heat a good sized room with that amp
>> on RTTY.
>>
>>> The power supply side seems cool - but then, that's with the cover on. 
>>> I don't know how hot is too hot and it would be useful to know at least 
>>> how much continuous power the supply is rated for.
>>
>> If you were running large glass tubes that depend on radiation that
>> cabinet would be too hot to touch.
>>
>> 73
>>
>> Roger (K8RI)
>>
>>> Tube cooling is probably another issue...
>>>
>>> Al
>>> AB2ZY
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>>
>>
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