Fan power issue

**PCBONEZ** · 06-03-2009, 01:54 AM

Re: Fan power issue

It's DC and it does say how many amps it is [indirectly].
Use Ohm's Law and do the math. - Volts and Watts are all you need.
.
Clue:
http://www.angelfire.com/pa/baconbacon/page2.html

**Krankshaft** · 06-03-2009, 02:53 AM

Re: Fan power issue

It is possible that the fan connector is driven using PWM via a switching transistor.

If this transistor failed open you will have no voltage to the fan.

Trace the positive terminal to the transistor and do a diode check test.

If the fan wasn't variable speed disregard the above statement.

If worse comes to worse and you can't find a 5V source you can always find a 12 volt one and install a little TO-92 voltage regulator to get the +5 volts.

You could always tap off the power jack as well.

**stevo1210** · 06-03-2009, 02:57 AM

Re: Fan power issue

I did the math and it's 0.06amps, which equates to 60mA. Should I splice the +5V wires of the CPU fan and connect the positive wire to that line? or is that down right dangerous since I could burn something? The CPU fan is 5V, 0.1A, 0.5W.

**stevo1210** · 06-03-2009, 02:59 AM

Re: Fan power issue

Originally posted by Krankshaft

If this transistor failed open you will have no voltage to the fan.

Trace the positive terminal to the transistor and do a diode check test.

That's what I think happened and I'm quite certain of it. Now even if that transistor is dead, I won't have the appropriate tools to remove it let alone install or source a new transistor.

**stevo1210** · 06-03-2009, 03:04 AM

Re: Fan power issue

Is the CPU fan connector able to handle the secondary fan along with the CPU fan or is that going to blow it?

**Krankshaft** · 06-03-2009, 03:10 AM

Re: Fan power issue

Originally posted by stevo1210

I did the math and it's 0.06amps, which equates to 60mA. Should I splice the +5V wires of the CPU fan and connect the positive wire to that line? or is that down right dangerous since I could burn something? The CPU fan is 5V, 0.1A, 0.5W.

If the CPU fan is variable speed and most laptop ones are.

You have to be concerned about exceeding the current the PWM transistor can supply. You don't want two dead fans.

Look for a 5 volt source on the HDD or DVD drive connecting ports solder the wire directly to the pins where they solder to the PCB. That should be a convenient tapping point.

You do intend to solder a wire right? If you're looking for some easy to tap off wire to splice into I think you're out of luck.

**stevo1210** · 06-03-2009, 03:17 AM

Re: Fan power issue

Yeah I'm going to solder the wire. I think I'll see if the DVD drive has any 5V current to it.

**Krankshaft** · 06-03-2009, 03:19 AM

Re: Fan power issue

I'm sure you can get a pinout for the DVD connector somewhere. Hopefully it will save you some time.

**stevo1210** · 06-03-2009, 03:20 AM

Re: Fan power issue

Hmm.... do any of you guys know where I can get a pinout for the optical drive connector for this laptop? it uses the common optical drive found in Latitude C series and Inspiron 4xxx series laptops.

**Krankshaft** · 06-03-2009, 03:24 AM

Re: Fan power issue

The 2.5 HDD pinout is more standard here:

http://www0.more-solutions.co.uk/support/hardrives.html

Pin 42 for +5V and 43 for GND should do it.

Be sure to test the points with a multimeter just to be sure.

The pin count starts from the right in the picture top row odd bottom even.

Ignore the 4 pin grouping at the far right thats for master / slave selection.

**stevo1210** · 06-03-2009, 03:38 AM

Re: Fan power issue

Originally posted by Krankshaft

The 2.5 HDD pinout is more standard here:

http://www0.more-solutions.co.uk/support/hardrives.html

Pin 42 for +5V and 43 for GND should do it.

Be sure to test the points with a multimeter just to be sure.

The pin count starts from the right in the picture top row odd bottom even.

Ignore the 4 pin grouping at the far right thats for master / slave selection.

Thanks for that. I have one problem though, my laptop HDD connector is like that, but it connects to the motherboard in a different way which is impossible to solder onto. So I decided to go and have a look at the connector which the optical drive connects to and I found like 4x 5V channels on there with the multimeter? I don't even know which one of those channels I should be using? Any ideas?

**momaka** · 06-03-2009, 11:14 AM

Re: Fan power issue

In case you need more options, I think USB ports also have 5v. Most should be able to handle up to 500mA. I'm not sure which pin would be the 5v supply, though, so you'd have to check that.

**PCBONEZ** · 06-03-2009, 11:18 AM

Re: Fan power issue

I think USB would be better.
Putting a motor on power to HDD with no EMI/Noise filters not such a great idea.

**Krankshaft** · 06-03-2009, 04:59 PM

Re: Fan power issue

I just got done crimping a RJ50 to USB data cable for my APC UPSs. No way I was gonna pay 30 bucks for something I can make for 3.

When I was checking the pinouts to make sure everything was right it hit me USB for the 5 volts. Guess you beat me to it PC

.

The USB A pinout is simple pin 1 is +5V and pin 4 is ground.

http://pinouts.ru/Slots/USB_pinout.shtml

Look at the diagram with the A next to it.

If the USB port is surface mount soldered and not through hole you'll just have to solder to the gull wings (the pins that solder to the surface of the board).

**stevo1210** · 06-04-2009, 03:11 AM

Re: Fan power issue

Done and done. I soldered a cable into the +5V line of the USB connector and she seems to be fine now. All fans work. Though I do have one question.... whats a good glue that I can use to stick that cable I just soldered?
I tried hot glue but it doesn't stick very well. I have a tube of Silastic which is a sillicone.... I know this sticks well.... but it is conductive or not?

Thanks.

**stevo1210** · 06-04-2009, 08:06 AM

Re: Fan power issue

Originally posted by stevo1210

I tried hot glue but it doesn't stick very well.

I take that back. My glue gun is crappy and it basically spews everywhere once switched on even without pressing the trigger. I think I'll need to get a new glue gun to do the job properly.... but is hot glue the *correct* thing to use in order to stick stuff to a circuit board? it is conductive? and what is the melting temperature?

**Wizard** · 06-04-2009, 08:07 AM

Re: Fan power issue

I use O2 safe silicone RTV.

Hot glue is NOT suitable! I had TV done with these and they wreak havoc on through-hole solder joints on the PCB in specific areas (where high freq subsonic vibration (like 15.7KHz and bit of heat that makes hot glue creep in first year to few years), and pulling connectors off slopped with this hot glue is a bear.

Hot glue in that said situation broke the solder joint between lead and the solder. It is documented, the same joints that didn't have this glue survived far longer. RTV is correct way to do this and does dampen vibration better and doesn't cold/warm-flow.

Cheers, Wizard

**stevo1210** · 06-04-2009, 08:11 AM

Re: Fan power issue

Originally posted by Wizard

I use silicone RTV.

Cheers, Wizard

My silastic tube says RTV 732.... does that mean anything? does this stuff eat through metals or is conductive or anything dangerous like that?

**Wizard** · 06-04-2009, 08:15 AM

Re: Fan power issue

I either use transmission RTV or ultra black, or clear RTV. Just a little. So you have air flow thru a notebook.

Cheers, Wizard

Fan power issue

Fan power issue

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