CurtPalme.com Home Theater Forum

enricho21 · Joined: 05 Dec 2007 Posts: 7 Location: Australia

Howdy, I've got an NEC 9PG and I've just replaced the three fans with quieter GlacialTech fans which run at a much slower speed of 1600 rpm & have a more ‘efficient’ blade/design. I’m now getting the message ‘Warning fans have stopped” 15 seconds after starting the projector and it is shutting down. I’ve got all 3 wires connected including the control wire. I’ve done some testing and determined that if I swap 1 fan for the new fan it still works but if I swap 2 or more of the fans for the new type the projector turns itself off.

How can I bypass the fan sensor circuit OR make the projector get the signal that it would receive from the original fans. Is the control wire based on voltage or ‘clicks’ from a fan rpm sensor. Thanks in advance for your replies & assistance.

kschmit2 · Posted: Sat Aug 30, 2008 6:42 pm Post subject:

I use a separate thermo control PCB with the stock fans. There are no "more efficient blade designs". The NMT or Sanyo fans are already efficient. You need a given RPM rate to achieve a desired volume per minute.

The thermo control board features 12 V fan init phase to securely start fans and reduce dust accumulation, has a voltage range from 5 to 12 V, linear voltage adjustment between 30° C and 50° C, and load stabilized output to be able to use it with almost any DC fan up to 2.5 W.

The 30° C to 50° C range is excellent imho. It ensures that as long as the temperatures are very moderate the fans will run slow, but once the temperatures rise, they'll run faster to take stress off components. 50° C for maximum speed is a reasonable temperature in that case.

Link to the thermo control PCB: http://www.noisemagic.de/pdf/thermocontrol/nmt-2/ver02/an_de-eng_screen.pdf

There's also a version of that controller that has a range of 28°C to 42° C.
http://www.noisemagic.de/pdf/thermocontrol/nmt-2/ver02/an_3_stecker_de-eng_screen.pdf

Kai

enricho21 · Joined: 05 Dec 2007 Posts: 7 Location: Australia

Thanks for the info. I've checked out the thermal fan controllers and in hindsight they would be by far the best option. Just to clarify the efficiency comment, what I meant was the db vs air volume, where I've noticed that some fans are louder than others for the same amount of air volume. The ones I've got are 35CFM, 19db at 1600rpm, which is a lot less volume than the originals but also quieter & slower than some other models for the same CFM. It’s also highlighted that I’ll need to keep a close eye on the operating temperature to make sure I don’t overheat the projector with less airflow.

I'd still like to try the slower GlacialTech fans that I've fitted which brings me back to the original question of how to either bypass the fan sensor circuit OR make the projector get the signal that it would receive from the original fans. Is the control wire based on voltage or ‘clicks’ from a fan rpm sensor.

rpruen · Posted: Sun Aug 31, 2008 12:53 pm Post subject:

The fan speed is 'clicks' as you put it. There may be more than 1 pulse per revolution of the fan, depending on the fan manufacturer.

The detection curcuit will be looking for a fan to be going at a resonable speed. It may be that your slow RPM fans are not going fast enough, and the projector sees this as fan failure.

If you have drawings of the fan detection circuit, then you may be able to modify it to be happy at a lower speed. Fan detection circuits can use many different possibilities. Ranging from digital (i.e. the controer brain looks at the pulses directly, or pulses from a devider more likley), to a simple frequency to voltage converter, and level sensing circuit.

All of these can likley be modified to work with lower RPM. For the devider example, the devider could be set to devide by less. For the voltage type you could change the voltage that triggers a fan failure signal.

Disabling the failure feature is not such a good idea, as stuff would likley die if a fan fails. However that should be easy, you may need to cut a wire/track on the board, and maybe add a pull up/down resistor to hold the line at the right voltage to say everything is ok.

If the fan RPM is fed direct to the controller, then you may not be able to do much, other than build an ocilator that pretends to be a working fan. You could then gate that ocilator with a simple fan detection circuit of your own, so that it shuts down when a fan fails.

Richard

Mark_A_W · Posted: Sun Aug 31, 2008 1:49 pm Post subject:

The fans NEC use are different to a PC fan.
It's a locked rotor detection, not a RPM detection, if I recall correctly.

Put the stock fans back, and add two or three slim fans to the deflection board.

PGs run too hot as it is - changing to less capable fans is a recipe for disaster...

kschmit2 · Posted: Sun Aug 31, 2008 4:05 pm Post subject:

rpruen · Posted: Sun Aug 31, 2008 5:43 pm Post subject:

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Each fan has 3 connectors. Pin 1 is 15v source through a 22 ohm resistor. Pin 3 is gnd. Pin 2 is the fan stop signal. It draws 5v standby through a 4.7 k resistor then clipped through a diode then off to the system board. Comes in the system board through SVC(24) then to driver ic 8283 then to CPU 8201. Good luck trying to manipulate that signal line. Laughing

**AnalogRocks** · Posted: Sun Aug 31, 2008 7:33 pm Post subject:

That just shows you how much engineering is in these things.

rpruen · Posted: Mon Sep 01, 2008 7:37 pm Post subject:

kschmit2 · Posted: Tue Sep 02, 2008 6:17 am Post subject:

Guys, the thermo controller I linked to works just fine and leaves all internal protection circuits fully intact. So why mess with the PJ and potentially fry it?

enricho21 · Joined: 05 Dec 2007 Posts: 7 Location: Australia

Hi, I read another post that indicated a 220uf electrolytic capacitor between the signal wire and the ground wire would stop the projector shutting down. I’ve tried this, having to put a capacitor on each fan lead, although there seems to one circuit for all three and some cumulative effect after the first two were done.

Despite the fact that I’ve got the slower fans working now and bypassed any safety I may have had with the fans stopping I still take the first reply that the air flow from the slower quieter fans will be less. I’ve done some calculations that show the original fans based on specs for the same size and type motor (Sanyo Denki 109 series motor, molded case, 2100rpm, 12 volt, medium speed) has 37.6CFM based on the spec of 1.04m/3 per minute. The new fans are rated at 35.8CFM which isn’t that far behind at 1.02m/3 per minute. I’ve also had confirmation from a PC magazine article that suggests the specs that the manufacturer published for the slower fans, at least for some of their other sized models are correct.

An hour before I did the comparison above I was ready to remove the slower quieter GlacialTech fans and replace them with the original Sanyo Denki fans and order the thermal controllers from Germany at about $100 AUD for the 3 including postage. Based on the comparison of air volume I’m going to go with the slower quieter fans and run the projector with the lid off for a while to see how it goes. I appreciate all the posts and I’ll let y’all know if it catches fire.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Ok. Let me try this one more time. When I said "Good luck trying to manipulate that signal line" , it was meant to be a deterrent, meaning dont try it. I know for a fact the signal can be manipulated but you must know exactly what needs to be done to keep the protection intact. And thats providing the replacement fans have the cooling capacity the projector requires. If you disable the protection and 1 fan fails, you end up with a boat anchor. Kia's post for thermo control is interesting but he's not indicating if he is still using the fan protection circuit. If not then I wouldn't recommend it either. The projector shuts down for a reason when a fan stops. Keep it that way unless your trying to blow it up so the wife will let you get a newer and bigger projector... Laughing