[Amps] Quieting a Henry 2K Classic X

[Donald Fox]

 Another thing that K7EM did was to install a step start circuit in the plate transformer primary circuit. The no longer obtainable (from Henry anyway) 1214 and 1171 plate transformers are scary expensive, and should have this (or a similar SS circuit) to protect them. The cost is minimal, and it is so much better not having the console thump loudly when first turned on. Henry began to include them in later production, which should have been from the get -go.

Don N8ECH
     On Friday, November 1, 2019, 9:49:04 PM EDT, Martin Sole <hs0zed at gmail.com> wrote:  
 
 Dennis,

I have here two of this exact amplifier, actually the export model but I 
believe transformer differences aside they are the same. I agree the 
blower is indeed quite noisy, though airflow I find is rather weak. 
Someone else obviously thought the same and cut a rough hole in the rear 
panel to install a 4 inch muffin exhaust fan. This does keep the amp 
cabinet to a reasonable temperature but just adds to the noise of 
course. Here in the 50Hz world our problems are somewhat compounded by 
the slower operating speeds of AC motors, around 20%. What that does is 
probably what you are suggesting in terms of reduced speed and it might 
be okay but I can tell you the cabinet does get mighty hot, certainly 
far too hot to touch the top of the cabinet even shortly after a 
transmission period. I'm not keen on that and have considered ways to 
increase airflow rather than reduce it. I recall someone used to say, 
air around a tube is a good thing and the only time you have too much 
air is when the tube will not stay in the socket!

You might look at the website of K7EM here:

https://www.qsl.net/k7em/henry_amplifier/henry_5k_blower.htm

Steve was likewise unimpressed by the noise coming from his amplifier 
and did some good work to improve it.

The amp is a 5k but apart from the tube and socket much of the rest of 
that amplifier is similar. It certainly uses the same blower. Steve used 
an anti-vibration tray with three mounts to support an EBM blower which 
uses a split capacitor arrangement to handle speed control driven by a 
thermal switch in the exhaust. All in all the mods Steve did look to be 
a good way to approach the 2K Classic X heat and noise.

I presume your amplifier, like mine uses the Johnson sockets for the 
3-500Z tubes. I think these are better suited to amplifiers with a 
lateral airflow like the SB-220 and L-4B whilst the Henry which is blown 
from under the base would be better suited to the Eimac recommended air 
system sockets which would seem to allow a much increased air flow 
around the base and tube envelope. I'm not an expert in any of this so 
maybe the increased turbulence caused by the more restrictive Johnson 
sockets helps base pin cooling? I am fairly certain that the Eimac 
recommendations for airflow are based around their suggested air system 
socket and not the Johnson one. Perhaps someone else can comment if 
changing the bases to improve airflow  and reducing the air might be a 
good move.

It will be an interesting project whichever way you go so do keep posting.

Martin, HS0ZED





On 02/11/2019 01:24, Dennis W0JX via Amps wrote:
> I have acquired a Henry 2K Classic X (domestic model) amplifier.  It uses a pair of 3-500Z's with chimneys. The very loud Dayton blower is driving me nuts. The Dayton blower is a model 2C915A, 3020 RPM, 230 volts and 140 CFM. This same blower is used when the larger Plate transformer of the Export model is installed. I suspect that this blower is much larger than required when operating at 1500 watts on CW or SSB.
>
> The standard blower in the 2K Classic was a Redmond 80239, 110vac unit. I cannot find the specs but I suspect it was around 90 CFM.
>
> I have researched several articles on about using a pair of 3-500Z's and the reference material shows a need for about 13 cfm per tube or 26 cfm total. Likewise, a 3-1000Z requires 4 cfm. I am aware that back pressure requirements play into this also.
>
> I read somewhere that it is possible to slow down a blower during standby periods by using a "split-capacitor" motor. Perhaps I have the phraseology wrong, but what I would like to do is have a blower slow down in speed significantly during listening periods and come up to speed during TX.  I operate mostly CW, little SSB, and do not use break-in/QSK so I could switch relays to do this.
>
> My other alternative is to install a smaller blower and risk shortening tube life. I do not contest very much nor operate continuous modes such as RTTY and FT8 at full power.
>
> Your ideas are welcome!
>
> 73, Dennis W0JX
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