[Amps] LK500 Question from New Subscriber‏

[Charlie Young]

Thanks to all who have responded so far to my query about the noisy LK500 fan and the cooling requirements for the tubes with transverse airflow. 

 

In case you think I am just sensitive to loud blower noise, this is not the case.  Besides this LK500ZB, in my shack at the moment there is a AL-1500, AL-82, LK-800A, Alpha 76PA, and a SB-220.  Although some of these have fairly loud cooling fan/blower noise, none of them bother me at all during operation. This LK500 fan is much louder than any of them. I don't have a sound level meter, but I would guess the LK500 is anywhere from 3 to 6 db louder than the Ameritron, and perhaps more.  I suspect a bearing problem or a fan blade out of balance. 

 

Based on the cooling requirements for the 3-500Z tubes using a blower and pressurized chassis with chimneys, and some info I found online about the airflow movement through a TL-922, which also has transverse cooling, my thoughts are that 50 CFM might be sufficient. 

A friend of mine has a new Papst TYP 4600X fan, rated 47 CFM at 85 volts and 54 CFM at 115 volts, which should bolt up in place of the present NIDEC TORIN fan.  The price is right also: free.  I am going to get this fan, power it up outside of the amplifier, and if it is quieter than the present fan will install it in the amplifier. 

 

If anyone thinks that 54 CFM might not be sufficient for transverse cooling of a 3-500Z pair, I would appreciate a heads up.  I have no problem buying a fan with higher capacity, if one is needed. 

 

Thanks again for the help, and I will advise the results of this swap if it is made in the LK500.

 

73, Chas N8RR    

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