Inactive lurker here, been so busy with my day job as a software guy, I haven't done electronics for a while.
Just in time for Christmas, the DC fans in my Sanyo Z4 projector broke down.
It's too old to be worth a paid repair job, so I'm going at it myself.
I need to replace two hard-to-find 70 mm 12V DC 3-wire fans.
They are called fan 1 and fan 3 (FN901 and FN903) in the service manual.
Both are NMB-MAT 2810KL-04W fans, but have slightly different specs.
Fan 1. 2810KL-04W-B39 2.28W 0.19A Sanyo part 645 078 8390
Fan 3. 2810KL-04W-B49 2.40W 0.20A Sanyo part 645 078 8383
I have not found these parts anywhere, and I would really prefer to change them for something better anyway, since they are very noisy.
The challenge is that 3rd wire is used by the projector, to verify that the fan speed is "not too low" -- as told in the service manual.
The projector shuts down immediately if it is not pleased with the fans' 3rd wire signal.
Here's the diagram for the fan control circuit.
Another diagram shows that the desired fan speed is a linear function of temperature, and there are three temperature sensors around the unit for this purpose.
Is there an easy way for me to fool this circuit that the fans are running well? A pulse generator of some sort?
I am willing to power the fans externally, and so would settle for a suggestion of how to please this circuit without even connecting these two fans to it.
Edit: I have found good alternative fans of the correct size, but lacking the 3rd wire.
If I understood this correctly, the fan 3rd wire signal must "match" the factory fans specs.
I'm guessing this is a linear map of expected pulses per second to PWM duty cycle. Is it really so?
As I mentioned above, I'm willing to use 2-wire fans and power them externally with manual speed control.
I guess I'm looking for a way might be to override or please the rpm and fan status part of above circuit.
I need to keep the temperature shutdown mechanism though, don't want to cook it.
I would love to have some help on this.
Ideas much appreciated!
Thanks.
Just in time for Christmas, the DC fans in my Sanyo Z4 projector broke down.
It's too old to be worth a paid repair job, so I'm going at it myself.
I need to replace two hard-to-find 70 mm 12V DC 3-wire fans.
They are called fan 1 and fan 3 (FN901 and FN903) in the service manual.
Both are NMB-MAT 2810KL-04W fans, but have slightly different specs.
Fan 1. 2810KL-04W-B39 2.28W 0.19A Sanyo part 645 078 8390
Fan 3. 2810KL-04W-B49 2.40W 0.20A Sanyo part 645 078 8383
I have not found these parts anywhere, and I would really prefer to change them for something better anyway, since they are very noisy.
The challenge is that 3rd wire is used by the projector, to verify that the fan speed is "not too low" -- as told in the service manual.
The projector shuts down immediately if it is not pleased with the fans' 3rd wire signal.
Here's the diagram for the fan control circuit.
Another diagram shows that the desired fan speed is a linear function of temperature, and there are three temperature sensors around the unit for this purpose.
Is there an easy way for me to fool this circuit that the fans are running well? A pulse generator of some sort?
I am willing to power the fans externally, and so would settle for a suggestion of how to please this circuit without even connecting these two fans to it.
Edit: I have found good alternative fans of the correct size, but lacking the 3rd wire.
If I understood this correctly, the fan 3rd wire signal must "match" the factory fans specs.
I'm guessing this is a linear map of expected pulses per second to PWM duty cycle. Is it really so?
As I mentioned above, I'm willing to use 2-wire fans and power them externally with manual speed control.
I guess I'm looking for a way might be to override or please the rpm and fan status part of above circuit.
I need to keep the temperature shutdown mechanism though, don't want to cook it.
I would love to have some help on this.
Ideas much appreciated!
Thanks.
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