[AMRadio] Screen Modulated 813


david knepper collinsradio at adelphia.net
Mon Dec 11 11:56:05 EST 2006


If you have one tube like aan 833A running slightly cherry and the other is 
not showing any color, then, the latter is a weak tube.  The former has low 
emission, in other words.

Dave, W3ST
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----- Original Message ----- 
From: "Geoff/W5OMR" <ars.w5omr at gmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Monday, December 11, 2006 11:23 AM
Subject: Re: [AMRadio] Screen Modulated 813


> Jack Schmidling wrote:
>> Jim Wilhite wrote:
>>> A bit of cherry red is ok.  Just remember what KYV said, don't exceed 
>>> the plate dissipation of the tubes.
>>
>> Roger but isn't color a function of plate dissipation?
>>
>> In other words, can one use shades of red as real world indication 
>> instead of relying on theoretical calculations?
>
> in short, no.
>
> some tubes 'color-up' at different levels than others.
>
> K5SWK had a pair of 833's in his modulator.. one always showed more color 
> than the other.
>
> Seems I remember a time when there were a pair, and one did -not- show 
> color at all, while the other one did.  He thought it wasn't working, but 
> it was proven that it indeed was.
>
> John/BXO has 4 813's in push-pull parallel in his modulator.. at normal 
> voltage, there's one that always showed 'a little color' when at idle.
>
> No, you can't depend on the color of the tube, to determine output of said 
> tube.
>
> --
> 73, etc
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