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Re: [Amps] Heat Dissapating 8877 HV Plate Caps

Subject: Re: [Amps] Heat Dissapating 8877 HV Plate Caps
From: Steve Thompson <>
Date: Sat, 25 Aug 2007 07:53:22 +0100
List-post: <> wrote:

> As someone stated, remove that cap and you will find a pinched-off tube which 
> was used during creation of a vccuum in the tube. The tube just looks nicer 
> with the cap. (the plate cap has nothing to do with the cooling of an 8877). 
> Check out the EIMAC Y-503, 8755, 8767, 8847A, ML8538/8933/8538B,Y-540, Y-654 
> for examples of the pich-off tube process (thas just a few of the TETRODES).  
> If you really want a plate/anode cooling fin look at the 3X600/Y-872.

Just to emphasise a point here - the cap that covers the pinchoff 
is thin metal, with barely any contact onto the rest of the anode 
metalwork. The heatflow into/through it is negligible. It 
certainly does not get hotter than the rest of the anode.

The add on radiator has horizontal grooves - even if there was any 
heatflow through the cap these would not do much in a vertical 
airflow. The cooler will be less ineffective if it's solid.

Even if such a cooler was used in a horizontal airflow, I doubt 
those grooves would do anything useful. They are too narrow. Air 
will go round, not through them unless it's very high pressure and 
applied from a narrow jet very close by.

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