[Amps] Quieting a Henry 2K Classic X

[Dennis W0JX]

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