TiVo Community
TiVo Community
TiVo Community
Go Back   TiVo Community > Main TiVo Forums > TiVo Series3 HDTV DVRs
TiVo Community
Reply
Forum Jump
 
Thread Tools
Old 06-08-2012, 12:41 PM   #1
Saturn
Lord of the Rings
 
Join Date: Apr 2001
Posts: 11,553
Eliminate TiVo fan noise (S3 and TiVo HD)

Ever notice a constant clicking from your TiVo? It is somewhat faint but can be heard easily in a quiet room such as a bedroom at night. Surprisingly, what you hear is probably NOT the hard drive, but rather the fan.

The TiVo uses Pulse Width Modulation (PWM) to drive the fan. So rather than adjusting the voltage from, say, 7V for low speed up to 12V for high speed, the TiVo sends pulses of 12V at around 32hz to the fan. The longer the pulse (and shorter the pause between pulses), the faster the fan spins. This has many a couple advantages for these types of fans, which I won't go into, but one disadvantage: At low speeds it causes the fan to "click" at that same 32hz.

This is a well-documented phenomenon:


http://www.silentpcreview.com/forums...pic.php?t=9340

This URL actually includes a circuit for fixing it too:
http://ww1.microchip.com/downloads/e...tes/00771b.pdf

However, that requires a capacitor, resistor and a transistor. My solution is much simpler.

Just add an appropriately-sized electrolytic capacitor in parallel with the fan. I've found that "appropriately-sized" is best found through trial and error. My S3 required only 7uF (4.7+2.2 in parallel) but my TiVo HD (with an after-market fan) required 47uF. If you select a value too small it won't do anything. If you use one too large, the capacitor will end up driving the fan while the PWM is off, resulting in a fan that runs at full speed no matter what the PWM is doing. Select just the right value and it "rounds" out the square-ish wave of the PWM signal which seems to prevent the motor of the fan from clicking while still allowing the TiVo to control the fan's speed.

Now, I'm not an EE but I did poke around with a scope to see the effects on the PWM signal, which I've attached for anyone interested.

Standard warnings apply: you will void your warranty taking apart your TiVo, and this is clearly a hack and may have detrimental side effects.

I can tell you that this has been running fine in my S3 for 4 months and my TiVo HD for... about 12 hours.
Attached Images
File Type: jpg Without capacitor.jpg (28.3 KB, 29 views)
File Type: jpg With 47uF Capacitor.jpg (29.8 KB, 27 views)

Last edited by Saturn : 06-08-2012 at 12:47 PM.
Saturn is offline   Reply With Quote
Old 06-08-2012, 02:07 PM   #2
dlfl
Cranky old novice
 
dlfl's Avatar
 
Join Date: Jul 2006
Location: Near Dayton, Ohio
Posts: 5,865
Interesting .... but what puzzles me is why they bother to vary fan speed at all. Why not just let it run at full speed? Hard to imagine they're worried about components running too cool. Trying to minimize air rushing noise? Minimizing power consumption? I would never have imagined any of these factors would justify the cost of the circuitry to control fan speed.
__________________

"It must be swell to be so perfect and odor-free" -- Del Griffith


VideoReDo users: Try
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

pyTivo users: Try
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
dlfl is offline   Reply With Quote
Old 06-08-2012, 02:54 PM   #3
Saturn
Lord of the Rings
 
Join Date: Apr 2001
Posts: 11,553
TiVo fans are pretty loud at full speed. They run full speed when you first plug them in, then sometime during bootup it will slow down (and start ticking).

I believe the S1s were just a 12v fan run at a constant 7V (with - connected to 5+ and the + connected to 12+...in other words, a huge hack), making for a nice quiet fan but they probably got too hot in enclosed cabinets and such.

Last edited by Saturn : 06-09-2012 at 11:23 PM.
Saturn is offline   Reply With Quote
Old 06-09-2012, 12:01 AM   #4
dlfl
Cranky old novice
 
dlfl's Avatar
 
Join Date: Jul 2006
Location: Near Dayton, Ohio
Posts: 5,865
I've never heard any kind of noise from my TiVo HD, including when it is first plugged in. I had an S2DT for 3 years too and never heard anything from it.
__________________

"It must be swell to be so perfect and odor-free" -- Del Griffith


VideoReDo users: Try
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

pyTivo users: Try
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
dlfl is offline   Reply With Quote
Old 06-09-2012, 11:08 PM   #5
Saturn
Lord of the Rings
 
Join Date: Apr 2001
Posts: 11,553
If you have a TiVo in your bedroom and your house is very quiet, the fan is very audible.
Saturn is offline   Reply With Quote
Old 06-09-2012, 11:54 PM   #6
steve614
what ru lookin at?
 
steve614's Avatar
 
Join Date: May 2006
Location: Dallas, TX
Posts: 10,722
I will corroborate with what dlfl says about the TivoHD. I have one in my bedroom and I don't notice any fan noise at all.

I have an unsubscribed Premiere that is a different story.
When booting up, the fans sounds like a jet engine powering up.
Once it calms down, I notice clicking noise you describe.

Does the capacitor(s) have to be electrolytic?
__________________
The Man Prayer: I'm a man ...... I can change ...... If I have to ...... I guess.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

F*CK CANCER!
steve614 is offline   Reply With Quote
Old 06-10-2012, 12:01 AM   #7
Saturn
Lord of the Rings
 
Join Date: Apr 2001
Posts: 11,553
Quote:
Originally Posted by steve614 View Post

Does the capacitor(s) have to be electrolytic?
I dunno. I didn't try any others. Give it a try and report back.

I think you'll have a hard time finding a large enough non-electrolytic capacitor to make a difference though. Digging through my box of parts the largest mylar capacitor I have is 1uF which I can pretty much guarantee won't do squat.
Saturn is offline   Reply With Quote
Old 06-11-2012, 06:12 PM   #8
unitron
Registered User
 
unitron's Avatar
 
Join Date: Apr 2006
Location: semi-coastal NC
Posts: 13,323
Quote:
Originally Posted by steve614 View Post
I will corroborate with what dlfl says about the TivoHD. I have one in my bedroom and I don't notice any fan noise at all.

I have an unsubscribed Premiere that is a different story.
When booting up, the fans sounds like a jet engine powering up.
Once it calms down, I notice clicking noise you describe.

Does the capacitor(s) have to be electrolytic?
The reason capacitors with a lot of capacitance (big uF number) are almost always electrolytic is that's the only way to get that many microFarads in that small a space.
__________________
(thisismysigfile)


"I am altering the deal. Pray I don't alter it any further."

Darth TiVo, 14 February, 2011
unitron is offline   Reply With Quote
Reply
Forum Jump




Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Advertisements

TiVo Community
Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
vBulletin Skins by: Relivo Media

(C) 2013 Magenium Solutions - All Rights Reserved. No information may be posted elsewhere without written permission.
TiVoŽ is a registered trademark of TiVo Inc. This site is not owned or operated by TiVo Inc.
All times are GMT -5. The time now is 11:31 PM.
OUR NETWORK: MyOpenRouter | TechLore | SansaCommunity | RoboCommunity | MediaSmart Home | Explore3DTV | Dijit Community | DVR Playground |