>
>> Why would the electrolytics in the AL-1500 require any special airflow
>> since
>> they are 105* C computer grade and meant to operate in a warm enviroment?
>> You once claimed that those caps were a special order of the highest
>> quality.
>
> The fact they say "105C* has NOTHING to do with being safe to run at 105
> or even being "meant" to work at 105. 105C is the absolute maximum
> temperature to fall within factory MTBF specs.
I never said that they should be run at that temperature. The fact that
Ameritron was smart enough to buy that extra overhead compared to cheaper
85* C caps is a big plus.
>
> Anyone working with electrolytics should be aware that the single most
> damaging thing to electrolytic life is ambient temperature. This is true
> for all electrolytics of that general material. There is a large decrease
> in life as temperature is increased. While voltage is a linear life
> shortening progression, temperature is a cube law effect.
Thats been well publicized for decades and holds true for old technology in
particular.
QUALITY caps specifically designed for switching supplies and other high
ripple use are amazingly long lived under adverse conditions.
Have you ever measured the temperature at the caps in the AL-1500?
In all the AL series of amps Ive worked on Ive never noticed excessive heat
in the PS area.
> The air system in the AL-12 series amplifiers (82,1200,1500) have 40-50
> watts total of bleeder heat above the electrolytics plus 35 watts of
> filament transformer heat dissipation, and it is important to not let that
> heat collect in that area.
All of the heat goes up. A bit of ventilation in that section of the cover
might help it from becoming trapped.
I like the idea of taking the tube heat straight up thru the rubber chimney
and out thru a low restriction mesh. It would reduce the RF component heat
somewhat. My 3CX1000A7 144 and 222 MHz amps are built that way and there is
no tuning drift which was quite noticable before adding the exhaust
chimneys.
Dennys LK-800A RF components run a comfortable warm with the 3 chimneys in
use. A big change from the DTR-2000L layout with the 8877 blowing right at
everything horizontally.
Carl
KM1H
> 73 Tom
>
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