Do I want a fan? - Page 2

Johan Potgieter · 13th October 2005, 11:10 PM

Nordic,

Now your first paragraph (air-flow matters) is a most interesting matter - caused me to contemplate for quite a while. Methinks I must adapt my advice re 2 fans somewhat......

I must admit that I had more in mind the kind of set-up where heat generators are distributed, i.e. there will be a gradient in cooling efficiency, being highest close to the fan and worse further on as the airflow diverges. There a "sucking" fan at the other end of the cabinet/duct will even things out. But in this case the air can be blown directly onto the heat generators i.e. the power tubes. Point taken. Two fans both blowing in would have a better effect (but I am not suggesting that Buliwyf's problem cannot be solved by only one fan; getting a bit pedantic, 2 smaller fans side-by-side will blow a broader stream of air....but OK). Good point by you.

But then: I would like to answer your PS question .... but cannot make sense of it!

(Is it the time of night??) Er...what transistors? If you mean the EL84s, I fear I still do not follow. Kindly explain!

(My PS: Greetings to Cape Town - I grew up in Malmesbury.)

buliwyf · 21st October 2005, 02:04 PM

update: I just removed the fans.

last night, after about 15mins of being in "standby mode," (fans running), I turned it on and cranked it up really loud (volume, drive, bass, mid, treble ALL at 10), for "authentic vintageness"

well, the Fuse for the output blew after around 3mins of playing.

could this be because that I cranked the amp up too loud BEFORE the tubes become really hot?

now its acting weird when its still not hot, making strange noises followed by a dive in volume followed by a growing feedback then total silence, then after 2 secs, its gona be normal again.

Bill*B · 21st October 2005, 10:58 PM

Just to mention what you may already know - check the spec sheets - some 24V DC fans will run happily at 12V, and the slower rotation speed at that reduced voltage keeps them quiet. Nelson Pass mentioned this in his DIY A75 sand amp, and I've adopted the practice. Bill.

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13th October 2005, 11:10 PM	#11
Johan Potgieter diyAudio Member Join Date: May 2005 Location: Pretoria, South Africa	Nordic, Now your first paragraph (air-flow matters) is a most interesting matter - caused me to contemplate for quite a while. Methinks I must adapt my advice re 2 fans somewhat...... I must admit that I had more in mind the kind of set-up where heat generators are distributed, i.e. there will be a gradient in cooling efficiency, being highest close to the fan and worse further on as the airflow diverges. There a "sucking" fan at the other end of the cabinet/duct will even things out. But in this case the air can be blown directly onto the heat generators i.e. the power tubes. Point taken. Two fans both blowing in would have a better effect (but I am not suggesting that Buliwyf's problem cannot be solved by only one fan; getting a bit pedantic, 2 smaller fans side-by-side will blow a broader stream of air....but OK). Good point by you. But then: I would like to answer your PS question .... but cannot make sense of it! (Is it the time of night??) Er...what transistors? If you mean the EL84s, I fear I still do not follow. Kindly explain! (My PS: Greetings to Cape Town - I grew up in Malmesbury.)

21st October 2005, 02:04 PM	#12
buliwyf diyAudio Member Join Date: Oct 2005	update: I just removed the fans. last night, after about 15mins of being in "standby mode," (fans running), I turned it on and cranked it up really loud (volume, drive, bass, mid, treble ALL at 10), for "authentic vintageness" well, the Fuse for the output blew after around 3mins of playing. could this be because that I cranked the amp up too loud BEFORE the tubes become really hot? now its acting weird when its still not hot, making strange noises followed by a dive in volume followed by a growing feedback then total silence, then after 2 secs, its gona be normal again.

21st October 2005, 10:58 PM	#13
Bill*B diyAudio Member Join Date: Sep 2004 Location: tampa, florida, USA	Just to mention what you may already know - check the spec sheets - some 24V DC fans will run happily at 12V, and the slower rotation speed at that reduced voltage keeps them quiet. Nelson Pass mentioned this in his DIY A75 sand amp, and I've adopted the practice. Bill.