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Fan on Amp Unbeatable

So, I have an older amp from the 70s. It's a solid state amp and the fan is so loud it's distracting. It's my first largest solid-state amp. I've been using tube amps for the last 15 plus years. I can't imagine fans are supposed to be overwhelming Lee loud. Has anybody else ran into this kind of issue and if so, how did you fix it?
pawlowski6132
don_c55
1,025 posts
 
Fans in SS power amps are because the designer was cheap when it came to heat sinks.

That is why there are so few with fans.
timlub
2,043 posts
 
I have had a few Pure Class A amps that got extremely hot and had fans.  I replaced the fans with high speed quiet fans,  then used resistors to slow them to a tolerable point for noise.  My amps lasted and lasted.  You might try that. 
sleepwalker65's avatar
sleepwalker65
832 posts
 
If the junction temperature exceeds 90 degrees C, your output transistors will have very short lives. You could monitor their case temperature with an inexpensive (read somewhat inaccurate but close enough for this purpose) IR non-contact thermometer. Refit with better heat sinks and use computer grade thermal compound. 
erik_squires
16,607 posts
 
You know, fans are quieter, especially when new now. :) Cheap too.
mijostyn's avatar
mijostyn
8,570 posts
 
You may be able to replace the fan with a fan exactly the same size that is quieter. Digikey and Parts Express have hundreds of them. Measure the voltage on the fan leads it is usually 110 VAC or 25 VDC. If 25 VDC you can wire a pot to it to adjust the speed then as Sleepwalker suggests track the temp on the heat sinks. I have had several amps like the Krell KMA 100 that had fans you couldn't hear.  
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