Dynaco ST-410 fan running way too fast. How to slow it down?

lowpoke · 7th April 2010, 02:29 AM

I just acquired a Dynaco ST-410 solid state amplifier that's working a treat, EXCEPT for the fan which is making waaay too much noise. The amp has been converted to operate on 240v and I'm wondering whether this has affected the fan speed. It looks to be the original fan which is meant to have two speeds, but seems to operate on an extremely high speed only.

I'm looking for suggestions on the best way to slow this thing down so I can actually hear some music.

lowpoke · 30th April 2010, 02:17 AM

OK, an update:
Fan is 230v AC brushless Rotron muffin fan. I was just about to install a series capacitor and a couple of 100K resistors in parallel to slow things down (as per quasi's post in another thread here) when I noticed what looks like a decent rheostat going cheap on ebay. I seem to recall reading that a rheostat won't work with a brushless motor. Can someone confirm whether this is the case?

(Rheostat is rated at 50W max, 2500 ohm. Fan is rated at 14W.)

7th April 2010, 02:29 AM	#1
lowpoke diyAudio Member Join Date: Mar 2009 Location: Australia	Dynaco ST-410 fan running way too fast. How to slow it down? I just acquired a Dynaco ST-410 solid state amplifier that's working a treat, EXCEPT for the fan which is making waaay too much noise. The amp has been converted to operate on 240v and I'm wondering whether this has affected the fan speed. It looks to be the original fan which is meant to have two speeds, but seems to operate on an extremely high speed only. I'm looking for suggestions on the best way to slow this thing down so I can actually hear some music. __________________ Show us what ya got at Homebuilt Hi-fi

30th April 2010, 02:17 AM	#2
lowpoke diyAudio Member Join Date: Mar 2009 Location: Australia	OK, an update: Fan is 230v AC brushless Rotron muffin fan. I was just about to install a series capacitor and a couple of 100K resistors in parallel to slow things down (as per quasi's post in another thread here) when I noticed what looks like a decent rheostat going cheap on ebay. I seem to recall reading that a rheostat won't work with a brushless motor. Can someone confirm whether this is the case? (Rheostat is rated at 50W max, 2500 ohm. Fan is rated at 14W.) __________________ Show us what ya got at Homebuilt Hi-fi

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