[Amps] Equalising the air flow on Commander 2500 tubes/replacement neoprene chimneys

[Steve Ireland]

Hi Jay

Thanks for the info – much appreciated.  It looks as though the Commander 2500 went through quite an evolution from its introduction to the later stages of production. I think this one is a later vintage from yours.

Vy 73

Steve, VK6VZ

From: Jay Sturtevant 
Sent: Friday, July 27, 2018 11:30 PM
To: Steve Ireland 
Cc: amps at contesting.com ; Phil Hartwell 
Subject: Re: [Amps] Equalising the air flow on Commander 2500 tubes/replacement neoprene chimneys

Steve, 

I have a Commander HF 2500, 1996 vintage, however, there are no chimneys on top of the 3cx800s and I do not have a "solid screen".

The amplifier you're describing may be a later vintage. 

I don't want to waste your time-- curious. 

Thanks!

Jay, K2ZT

On Fri, Jul 27, 2018, 10:13 AM Steve Ireland <vk6vz at arach.net.au> wrote:

  G’day everyone

  A good friend of mine has recently acquired a Commander 2500 which is need of repair/rebuild after a long and hard life.

  On taking the amp apart, he noticed one of the neoprene chimneys on the (two) 3CX800 tubes was more melted than the other.  He then put the amp’s fan on and discovered the tube with the more melted chimney was receiving considerably less air flow than the other, owing to a screen placed between the two tubes.

  A potential solution was to replace the solid screen with a mesh one, but I said it was likely that someone on this reflector had already come up with a solution/modification to solve this problem and I’d ask for him.

  It also occurred to me that someone may know where some suitable neoprene can be purchased, so he can make replacement chimneys for the two tubes.  Any ideas on this would also be approached.

  Vy 73

  Steve, VK6VZ  

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