I have a Crown comtech amplifier. Fan runs at full speed. My other comtech fan slows down according to heat. This one wont, and its loud can I add a resistor to bring it 1/2 Speed?
Possibly, but the amplifier may overheat if you do. There may be an internal fault
causing excessive heating, and the need for full fan speed.
causing excessive heating, and the need for full fan speed.
DC4.5V~35V 6V 12V 24V 5A PWM Motor Controller Speed LED Regulation Dimmer 20khz | eBayI use one of tho bring down the fansped in a tube amp.
There could be a problem with the fan speed circuit. Maybe its designed go full speed if something fails.
No the amp rarely builds up any heat at all something in the amp circuit control went out read the amps service manual no mention,
Thanks for the speedy relies!
its a 120 volt AC motor
Thanks for the speedy relies!
its a 120 volt AC motor
Then check the other amp, on computers the fan is DC, and you have an option to control fan speed, which is done by PWM, or others.
Those fans have 3 or 4 leads, 2 for power, one for sensor and 4th for PWM if the fan itself has PWM inside.
It may be that a previous repair person decided to put an AC fan...
Thing is, DC fans have a circuit to convert DC to AC, then turn a regular solid shaft motor (like a squirrel cage for example).
The circuits fail, or maybe they did not have a DC fan handy, might be that it was done at the factory.
You could use a series capacitor, 0.1 uF 400 volts plastic potted, not the aluminum can ones, to reduce the speed, it works. dont let the speed go too low, could blow fan if current is excessive.
This one may be in parallel to the mains supply, not through a control circuit.
And AC fans give more flow, that also may have influenced the decision.
If needed, lube it up, there is a small rubber cap under the sticker, put a little grease and engine oil, work the shaft in the shaft direction, cap up, clean off excess lube, and put the sticker back in place, or use tape to keep the cap in place.
Those fans are pretty quiet, could be a dry bearing.
And do keep us updated.
Those fans have 3 or 4 leads, 2 for power, one for sensor and 4th for PWM if the fan itself has PWM inside.
It may be that a previous repair person decided to put an AC fan...
Thing is, DC fans have a circuit to convert DC to AC, then turn a regular solid shaft motor (like a squirrel cage for example).
The circuits fail, or maybe they did not have a DC fan handy, might be that it was done at the factory.
You could use a series capacitor, 0.1 uF 400 volts plastic potted, not the aluminum can ones, to reduce the speed, it works. dont let the speed go too low, could blow fan if current is excessive.
This one may be in parallel to the mains supply, not through a control circuit.
And AC fans give more flow, that also may have influenced the decision.
If needed, lube it up, there is a small rubber cap under the sticker, put a little grease and engine oil, work the shaft in the shaft direction, cap up, clean off excess lube, and put the sticker back in place, or use tape to keep the cap in place.
Those fans are pretty quiet, could be a dry bearing.
And do keep us updated.
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For long life, and quiet, sleeve bearings work OK, but they can fail in short circuit when the bushes wear out.
I stick to ball bearing fans, noisier but safer than a blown controller.
And the 4" fans run quieter than 3" fans.
Have fun
I stick to ball bearing fans, noisier but safer than a blown controller.
And the 4" fans run quieter than 3" fans.
Have fun
Your other one speeds according to heat, but the "bad" one is on full all the time? Rather than adding stuff to slow the fan down, why not try to find out what is driving the fan to full speed in the first place? The amp may not be running hot, but the fan could be responding to something else, or the fan drive circuit could have a problem. The fan can't tell the difference between a overheated amp and an amp with a bad heat sensor.
@Enzo...
It is a 120 V AC fan, and a controller for that is not easy.
I think somebody changed the fan from 12 / 24 V DC to mains, for whatever reason.
Please let him check the other 'good' one and update us.
To put a triac or SCR based fan speed controller in a consumer unit is pretty unusual, it will be controlled by a temperature sensor of some kind.
Let the OP tell us what is going on.
It is a 120 V AC fan, and a controller for that is not easy.
I think somebody changed the fan from 12 / 24 V DC to mains, for whatever reason.
Please let him check the other 'good' one and update us.
To put a triac or SCR based fan speed controller in a consumer unit is pretty unusual, it will be controlled by a temperature sensor of some kind.
Let the OP tell us what is going on.
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Step less fan regulators use BT 131 /136 /139 Triacs fired by a diac, the control is through a pot.
In this application, the pot is substituted by a temperature sensor, and that means a circuit with mains voltage inside the unit.
That high voltage unit needs to be shielded from unwary repair people with metal tools.
And you have DC supply available, safer to use a DC system, the variable speed system for CPU fans has been on motherboards for about 20 years.
He mentioned a 120 volt fan, which was unusual.
Let the OP tell us after checking the other unit what has been going on.
Either somebody rigged a fan through the main switch, or the circuit has failed to short circuit rather than open.
In this application, the pot is substituted by a temperature sensor, and that means a circuit with mains voltage inside the unit.
That high voltage unit needs to be shielded from unwary repair people with metal tools.
And you have DC supply available, safer to use a DC system, the variable speed system for CPU fans has been on motherboards for about 20 years.
He mentioned a 120 volt fan, which was unusual.
Let the OP tell us after checking the other unit what has been going on.
Either somebody rigged a fan through the main switch, or the circuit has failed to short circuit rather than open.
A little clarification...
I meant fans as in room ceiling fans, later the changes to the regulators were to using a switch with fixed resistors to control the triac, instead of the pot.
Later still a set of 400V capacitors was used in place of the triac circuit, it wastes less energy, and in some fans the hum created by the triac was eliminated by the capacitor design.
The capacitor design is simpler, just a switch and capacitors, so much cheaper to make.
By DC fan I mean a low voltage 12 / 24 V DC fan, sometimes 48 V are also available. In computers, the CPU and sometimes chassis fan are controlled by circuits on the motherboard.
That is an easy solution for the desired result of controlling the amplifier temperature, compared to a mains voltage circuit.
Of course the simplest would be a thermostat in series with a mains operated fan...
I meant fans as in room ceiling fans, later the changes to the regulators were to using a switch with fixed resistors to control the triac, instead of the pot.
Later still a set of 400V capacitors was used in place of the triac circuit, it wastes less energy, and in some fans the hum created by the triac was eliminated by the capacitor design.
The capacitor design is simpler, just a switch and capacitors, so much cheaper to make.
By DC fan I mean a low voltage 12 / 24 V DC fan, sometimes 48 V are also available. In computers, the CPU and sometimes chassis fan are controlled by circuits on the motherboard.
That is an easy solution for the desired result of controlling the amplifier temperature, compared to a mains voltage circuit.
Of course the simplest would be a thermostat in series with a mains operated fan...
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I guess one channel fan broke, probably the controller which is complex and must be "understood", so Plan B to keep the amp working was to fit the simplest fan of them all: a 120VAC fan which works on it own.
Of course, **fixed speed** , but better than nothing.
That fan is not designed for speed regulation so don´t waste time trying, doubly so because such regulation MUST track heat sink temperature.
Forget it.
Eiher stand the fan noise or grab schematic and troubleshoot fan circuit, there is not an intermediate solution.
Of course, **fixed speed** , but better than nothing.
That fan is not designed for speed regulation so don´t waste time trying, doubly so because such regulation MUST track heat sink temperature.
Forget it.
Eiher stand the fan noise or grab schematic and troubleshoot fan circuit, there is not an intermediate solution.