Members onthee brink Posted December 5, 2016 Members Share Posted December 5, 2016 I have a Roctron Velocity 300 and it looks like the fans aren't turning on to cool it. I opened it up and checked the connection to the fan. The plug was off set and it didn't appear the fans were getting power. I reset the plug into the circuit board and plugged in the fans. The problem is I don't know if I'm getting it hot enough for the fans to turn on when the cover is off. Does anybody know where the temperature sensor is so I can maybe put some heat on it and try to get the fans going? I like to know what the issue is before I take it to a repair guy. Link to comment Share on other sites More sharing options...
Members Mikeo Posted December 5, 2016 Members Share Posted December 5, 2016 Many Digital Volt Meters come with a temperature sensor. http://www.testequipmentdepot.com/bk-precision/multimeters/2706b.htm?gclid=CjwKEAiAvZTCBRDvnoOaoa2j3xISJABxPjN9GFt_sTJlUJDTE6DCOyhyGZgiYBrnHtlWSUCy0hI4VhoConnw_wcB I'd look for one that has a small capacitance bridge on it too. They are good enough for many applications. Link to comment Share on other sites More sharing options...
Members onthee brink Posted December 5, 2016 Author Members Share Posted December 5, 2016 I need to test the sensor built in to the unit. It controls the on/off for the cooling fans. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted December 5, 2016 Members Share Posted December 5, 2016 Theres no way you are going to be able to go in there and bypass the sensors if you don't know what you're doing. Thermal sensors come in all kinds and shapes. Many are variable resistors that change resistance with temperature. The board looks at the resistance changes and turns the fans on depending on what resistance is read. Fans usually go out long before you ever have a problem with thermal sensors. Thermal sensors go bad the unit probably wont power up. Most amps have fans run at low speed when the amp is at normal temp and kick them up to high speed when the heat sink gets to a certain temp. Some even provide a variable speed. If you get no fans when running the amp and the heat sink is hot to the touch, then there might be something wrong. Get the amp checked. The problem may have nothing to do with the sensors. You can have thermal breakers that are open, fuses, power supply, etc. The only thing you can and should look at are the fans themselves. The fans should spin real easy and a with a quick spin they should continue to rotate a few times. If they come to a quick stop the bushings/bearings may be gunked up. Fans draw in dust and the bushings/bearings can get clogged up. Depending on the type they may have a sticker/seal over the shaft end. Sometimes a drop of oil on the shaft end is all you need to get them working again. You can try giving them a spin with power applied and see if they will kick start. Computer fans get gunked up like this all the time. If you can kick start them then a good cleaning can usually keep them running for awhile. Otherwise a replacement may be needed. Fans will act like a generator by the way. If you connect the fan terminals to a love voltage meter, then spin the fan, you should see a voltage on the meter. This may not tell you if the brushes are good or if its got a bad coil in the stepper type but it will tell you if its completely dead. Many of the ones I work with just wear out and replacement is the only option. From this pic it looks like they are those cheap computer fans. They are made of plastic and fail quite often. Google up the part number and find replacements. They should only be a few dollars each. If you cant find anything get be a close up shot on the labels so I can see what type and voltage they are and I'll see what I can find you. I deal with this stuff on a daily basis and may have something that will work around the shop here. Give the thing a good blow gob with a can of air or a compressor too. Dust is an enemy of electronic gear. Keep it clean and it will last allot longer. Link to comment Share on other sites More sharing options...
Members onthee brink Posted December 5, 2016 Author Members Share Posted December 5, 2016 Thanks WRGKMC. I got the schematic and it looks like that little circuit board connected to the fan is the sensor. Due to poor design when you try to put it together the plug slots in between the fins on the heatsink often disconnecting making it very difficult to tell if it's broken or just unplugged. With it open its too far away to test to see if it's working. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted December 7, 2016 Members Share Posted December 7, 2016 There's more then one way to skin a cat. Plug it in while its open and put a hair dryer on it to heat it up. When it gets hot enough the fans should kick on. Link to comment Share on other sites More sharing options...
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