asked Jan 19, 2006 at 8:55am
Hp HP LaserJet 5SI

HP LasetJet 5si Making Noise

Dear FYOP,

I have a customer that has a laserjet 5si that is making a high pitched 'dog whistle' noise.
When it's powered on, the lights come on, they gears cycle then stop, then a the noise starts. It lasts for about 3 to 5 seconds, then stops.
I KNOW it's not anything in the gears, because it doesn't happen while the gears are actuating. I KNOW it's not the mirror carousel, because it doesn't make the noise while it's printing. I KNOW it's not the toner cart, cause it took it out and still get the noise with no cart in the printer.
I pulled off the back cover, thinking it might be something(?) in the power supply, but I just can't locate the noise.
Customer says it does this every time it comes up from sleep mode, or when power is cycled.


I replaced a couple of delivery assemblies with a loud sqeaking noise. Do you think it could be coming from there?
by Anonymous on Jan 19, 2006 at 9:02am Add comment
No, it's not from the top of the printer. It's really hard to spot exactly where it's coming from. Almost sounds like the very center. Once it warms up, it cruises along just fine.
by unknown on Jan 19, 2006 at 9:25am Add comment
There's a fan up there, could be coming from that. You do realize, we can only guess since we're not there. Only way to find it is to take covers off and bypass door interlocks and listen where you think it's coming from.
by moe on Jan 19, 2006 at 9:34am Add comment
Have you tried manually rotating the fuser?
by Anonymous on Jan 19, 2006 at 9:35am Add comment
Dear Moe,

Yes, I do realize you can only guess, I just wanted someone else to help me think this one out.
I'm researching the service manual right now as well, and I'm beginning to lean towards a fan somewhere as well.


by unknown on Jan 19, 2006 at 9:36am Add comment

Replaced the two innermost fans on the printer with no change.
After having the printer powered off for 5 minutes, I unplugged one of the fans and powered up. No Noise! I did get the fan failure message, but not the high pitched 'dog whistle'. This has got me to thinking it may be the dc controller board.
Any opinions on this one?
by unknown on Jan 24, 2006 at 7:22am Add comment
fuser bearings make this noise.remove the fuser and rotate it manually. Of course wait til it cools down.
by JWB on Jan 24, 2006 at 12:21pm Add comment
dc controller is only that a controller. It does not make noise. The fan you unpluged is most likely the culprit. My guess it is the fan next to the laser/scanner because that is the one which usually goes. Keep in mind that the item which is making the noise may not have even fired due to the fan being disconnected. Sometimes a critical error will cause other items not to function.
by dmzcompute on Jan 24, 2006 at 2:23pm Add comment
Visited the customer today for a different printer, but asked about the 5si.
Turns out, it had something to do with where the printer was sitting. They moved the printer 10 feet towards the door and the noises stopped!
Go figure....
by unknown on Mar 9, 2006 at 2:57pm Add comment