[Amps] GU-84B Cooling

[Will Matney]

Dick,

I'm not saying it's a bad tube, and dont want none to think that. I just dont want anyone to undercool the tube so it will last. Who knows, the 4CX1500 may have an over-sized radiator too! About the only way to tell about the temp would be to use a thermocouple connected to the anode. Then the temp read under contesting conditions both under SSB and AM using the air flow they recommend. AM/CW creates a good bit more load on one as does SSB transmissions. Then if the temp stays down where it should, one would know it would be ok. I'm like Rich, and what George mentioned, use the largest blower possible. Another thing too is maybe mount and external blower and duct it to the amp. You can set one of these in another room to help kill the sound down if it's a concern. On yours, you may have the right combination by using enough fans both pushing and pulling. Have you measured what the air flow and pressure is on your amp? If so, let us know so we all have a starting point.

Best,

Will

----- Original Message -----
From: PA3DUV <pa3duv at planet.nl>
To: "Will Matney" <craxd at engineer.com>
Subject: Re: [Amps] GU-84B Cooling
Date: Tue, 19 Jul 2005 22:45:03 +0200

> 
> Will,
> In my twin tube GU84B amp one fan is used to pressurize the 
> subchassis and two axial fans to draw the air out.
> With a B+ of 2900 VDC, from the 3 phase PSU the two GU84B tubes 
> generate an easy 6 kW of output. During normal (6 dB compressed) 
> SSB transmissions the exaust air stays below 55 degrees celcius.
> Cheers, Dick Knol
> PA3DUV
> 
> 
> 
> ----- Original Message ----- From: "Will Matney" <craxd at engineer.com>
> To: <amps at contesting.com>
> Sent: Tuesday, July 19, 2005 9:53 PM
> Subject: [Amps] GU-84B Cooling
> 
> 
> > On a webpage somewhere, I cant remember now where, I read about 
> > the GU-84B (4CX1600) having an undersized radiator. I think it 
> > was on a Russian amateur website. What I had read was this tube 
> > was actually designed for running in a missle by the Russians, 
> > and was designed for a 1 time use. So, they undersized the 
> > radiator a good bit because of space limitations. They were 
> > making the comparison to a 4CX1500's radiator size being larger 
> > in the discussion. However the guts of the GU-84B supposed to be 
> > really good. So this brings the delima of how to cool it so one 
> > would get a long life out of it. One way would be add some sort 
> > of extra aluminum heat fins, or some made of brass, with fins 
> > sticking out to catch more air, thus increasing the overall 
> > surface area. The only other way would be to increase the amount 
> > of air flow and volume over the fins that's there. When doing 
> > this though, the noise goes up from the blower. However, if one 
> > is going to dealve into using the GU-84B, I'd s
> > uggest looking into this and compare the sizes between its 
> > radiator and the one for the 4CX1500. Even though the tube is 
> > cheaper than some others, it's still expensive if you have to 
> > re-tube all the time. If I can remember where I seen this, I'll 
> > post the link.
> >
> > Best,
> >
> > Will
> >
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