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Re: [Amps] Equalising the air flow on Commander 2500 tubes/replacement n

To: "Jay Sturtevant" <k2ztdx@gmail.com>, "Steve Ireland" <vk6vz@arach.net.au>
Subject: Re: [Amps] Equalising the air flow on Commander 2500 tubes/replacement neoprene chimneys
From: "Carl" <km1h@jeremy.qozzy.com>
Date: Sat, 28 Jul 2018 09:51:24 -0400
List-post: <mailto:amps@contesting.com>
Is that a Command built or Palstar built amp? A very visible Palstar change is the air holes added to the front face of the RF chassis to cool the PS board which was easily fried and a royal PITA to access..

Palstar made many changes to the RF deck but what you describe is one I have not seen in the many amps Ive serviced....especially the no chimneys version. That sounds more like a Hammy Hambone job.

Carl


----- Original Message ----- From: "Jay Sturtevant" <k2ztdx@gmail.com>
To: "Steve Ireland" <vk6vz@arach.net.au>
Cc: <amps@contesting.com>; "Phil Hartwell" <vk6gx@yahoo.com>
Sent: Friday, July 27, 2018 11:30 AM
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@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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