[Amps] re cooling of coils

[Will Matney]

Rich,
What is poor, is those junky 11 meter solid-state "contesting amps" 
floating around with better cooling than any amateur amplifier made now! 
The innards may be junk, but by cracky they do add the fans to them. 
I've seen as high as four 4-3/4" high output muffin fans mounted on a 
1kW model. Take a look at some of these on ebay and you'll see what I 
mean. I've seen some tube models in them with both a blower and a fan on 
top of the chassis too. The thing is, a 4-3/4" muffin fan can be bought 
new pretty cheap these days. Even open type "refrigeration fans" like in 
the SB-220 aren't that expensive. Here, I can buy a new fan motor for 
about $9.00 and the blade for about $1.50.

Another thing these manufacturers look at is the holes punched in the 
chassis. The holes cost so much a hole but on a CNC punch, they're about 
5 cents a hit (I used to design tool and die for a trailer parts 
manufacturer). Now it don't cost much to add an opening. Even a 4-3/4 
inch hole for a muffin fan might cost a whole $1.50 to make. To mount a 
open type fan, just two transformer brackets is all thats needed. They 
cant claim it's engineering cost because I can lay out a complete 
chassis in 1/2 days time, by CAD or on the board.

Also, I've checked the wire size of the inductors in some popular 
amateur amplifiers. What I found, well, was ridiculous. With the RF 
current needed, the size of the wire was too small. Even the hook-up 
wire was too! I wont name any amp names but if all here would 
investigate them like I have, you'll find the same as me. I'm sure you 
have from the website you have up and past articles I've read.

About the only way to really get one that will last and last is to build 
it ones self. Then, Uncle Sam tries to make this extra hard because the 
manufacturers have them in their pocket, along with some other 
organizations which I won't get into here. I would like to encourage 
every amateur to publish any work they've done on any subject. Anything 
to make home brewing easier may make the manufacturers take notice. Any 
drawings, schematics, and pictures of the finished amp would make one 
Jim Dandy webpage. Heck, I took the time (about 1-1/2 days) to write the 
web pages on winding transformers. It's not hard and don't have to be 
pretty. Any info like this is valuable. I'd like to see somebody set up 
a web server where everyone could submit work on amps and amp related 
articles. Especially without making someone to "join" their organization 
and pay for access to the goodies. This makes me question some of these 
organizations who claim information to amateurs should be free. If it 
wasn't for a copyright infringement case, I'd post it all.

Sorry, I'm done spouting off. I will still do all I can to help anyone 
who needs it. If it's a question within my power to answer. Also, a big 
thank you to those on here who have helped me with questions I have 
pondered about.

Will Matney


R. Measures wrote:

>
> On Sep 5, 2004, at 4:31 PM, Will Matney wrote:
>
>> Really, the cooling of the tank circuit can be done numerous ways. 
>> However, amateur equipment manufacturers look at the cost. They want 
>> to build an amp that they can get the most out of with the less 
>> innards. Actually, just sizing the conductors to a large enough value 
>> is all thats needed in most cases.
>
>
> The irony is that it takes little air flow to prevent tank inductances 
> from having heat problems.  As I see it, not directing forced air at 
> tank inductances is not good engineering practice.  Examples of well 
> thought out mechanical designs for an amplifier are the TL-922 and SB-220
>
>> The manufacturers try to get buy with the least sizes over one thing. 
>> cost. Just like Alpha offering a fan for an option. Why not put the 
>> fan in as standard if it's needed?
>
>
> A better fan is not needed in Antarctica?
> t
>
>> The sodium idea was good for transferring heat to the mass of the 
>> head on the valves like was mentioned The molten sodium would flow 
>> due to the differences in temperatures. Sodium becomes liquid has a 
>> low melting point, but higher than what water boils at. Sodium 
>> Hydroxide (Lye) will boil with water at 180 degrees when the 
>> saturation is mixed correctly and is used to blue steel. It has been 
>> used in other industrial applications, including cooling. A 
>> refrigerant could be pumped through a coil to do this too, with a 
>> heat exchanger on the other end with a compressor. Even water could 
>> be pumped through one or the coil be immersed in oil. I think Hal 
>> mentioned the vacuum cleaner hose to route an air flow onto a coil. 
>> If it wasn't Hal forgive me, my mind is short as other things 
>> sometimes. When amps are designed, an experienced designer takes all 
>> this into consideration or should. Some doesn't and is seen in the 
>> final products.
>>
>> Generally, fan cooled amps have better tank cooling than do blower 
>> cooled amps. In my opinion, a fan should be used with a blower to 
>> cool one correctly. Not only does tank components need cooling, the 
>> large HV electrolytic capacitors do too.
>
>
> In 200kW+ amplifiers, the tube, vacuum capacitors and tank inductances 
> are typically water-cooled.  It is not unusual for such an amplifier 
> to have a 100-gallon per minute water pump as well as a centrifugal 
> blower cooling the filament seals.
>
>> Heat is the #1 killer of these. Transformers benefit from an air flow 
>> across their coil. Really, any part subject to heat will benefit. 
>> What's the price of one fan compared to maybe X2 the life span of the 
>> amp? But, if the amp wouldn't wear out, they wouldn't be able to sell 
>> more after a while.
>
>
> Which is why one must build a nearly perfect, no-compromises 
> amplifier.   The good news is that doing so promotes one out of the 
> "appliance operator" category and it for sure beats the hell out of 
> watching "Gilligan's Island" reruns or "reality TV".  .
>
>>
>> Will Matney
>> _______________________________________________
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>> Amps at contesting.com
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>>
>>
> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>
>
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