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Vintage threads from the first ten years

9/13/1997 1:16 PM
R.G.	Re: AC30 trany layout The whole trick with fans is to keep the fan just turning over, not running at full speed. This means that it runs quiet and still moves enough air to keep the tubes and other things cool. There are two ways to do this. One is to use a DC fan and run it from rectified filament voltage, which makes about 7.5-8Vdc to run a 12Vdc fan, or to use a 240VAC fan running from 120VAC. In both cases, the fan is fed about half or a little over of it's rated voltage and runs very quietly. DC 12V fans are a lot easier to find and come in a larger range of sizes and shapes, but then you have to rectify the filament to get the DC to run it on. The primo way to do fan cooling is to find a place to put the fan where it can evacuate the whole chassis, and then put inlet louvers beside whatever you want to keep cool. This isn't usually necessary for guitar amps, thankfully, as it will fully mess up a good cabinet. you can just put the fan where it will blow across the power parts - the output tubes, the rectifier tube, and the power/output transformers. Even a slight bit of air movement around these parts will get the temperatures down a lot, maybe to the point where you can touch the output tubes with a bare finger! I saw one installation where the fellow just used a couple of L-brackets to mount the fan standing up on the chassis. It was quick and easy, only two small holes, and did the cooling just fine.

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