CurtPalme.com Home Theater Forum

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

Hello All I just thought I would contribute something to help all out there that would like to quiet down the marquee.
This makes it easy to install regular 12v pc fans into a marquee. I installed and running in my marquee without any rise in temps. It has been running for about 2 years no problems, and is whisper quiet. If you have any questions feel free to ask.

Happy modding

John

1031 · Joined: 22 Mar 2006 Posts: 657 Location: Finland

I have done fan mod (many many versions...) And i must say that best way (safest) is to use 24v fans. Same 24 volt goes to gonvergence section and if you put 3*12v fans on belly and use regulator to drop 24v down to 12v . That fan/regulator combination takes allmoust twice mucs amps that tree 24v fans takes. Also magnetic shielding is something that you should look, cheap fans for computermodding are not shieldet good. Those belly fans are quite close to focusyokes and you all know that focusyokes are used also for rastercentering. That rotating magnetic field can make rasters quite unstable.
Right now i got still some unstablenes, even that i got good Papst fans, that is probably because that higher current draw (i havent tested that yet) . Before papst i used Silenx (older/never models etc..) then i ordered those Papst (4412F2GL), sadly those 12v versions. That was my bad, i measured that current draw after..If i must do fan mod from beginning, i defenitly go for 24 volt versions.
Also that db rating, those papst are rated 26 db, sounds loud.. No, those papst was more silent that 14db silenx fans...

That was my case, many others have done fan mods without problems.

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

honestly i have been running it for a long time an my raster is stable. if you look on the avs site in the archives you can see the reviews by people who did the mod.i did this mod even before the pics i took it apart because some people wanted pics. I know of about 15 people who use this mod. as long as the ground is proper you will not have excess draw. Also it actually takes less power than you think. to half -24 to -12 you are using slightly more than half of the total current of the fans in this case approx .25 amps at -24 volts the stock fans use more than this. so you are actually saving on the power. I know they are not the quietest fans out. But the flow of air at pressure is as good if not better than the stock fans.

I do understand this may not be for everyone just something for people who like to tweak.

1031 · Joined: 22 Mar 2006 Posts: 657 Location: Finland

Yes i know that many has done fan mods without any similar problems that i got Question

Maybe there are difference (lvps versions) that how much those can give current on that-24 volt line.
I really never ment to say that "your fan mod is bad"or nothing like that.

That was just my case, and its still little mystery why i got that "raster unstableness" its not so bad that you can see it to viewing position, but closer to screen that is visible. Maybe i must test to run those belly fans with external powersupply.

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

no no i never took it that way. we could see if you have a different power supply version to rule one thing out. I am at work at this time but when i get home i will post the part numbers and revisions of my lvps for bolth projectors. you could also check your connections on the boards as well as reseat the boards. I have found they have a tendancy to loosen up on the marquee especially if it is hanging. one of the first things i do is clean every contact with contact cleaner to make sure that they are totally clean and free of dirt. just make sure you let them dry very well before reassembly.

Joust · Posted: Sat Jan 26, 2008 2:58 pm Post subject:

May I recommend putting two 12v fans in series thus making the pair 24v. put series pairs in parallel.
you get the best of both worlds.
The only drawback is, if one fan fails they both do. So I would put an LED for each pair to sense fan failures. this would give you a warning light.

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

that does work however if you get a fan fail you could possiably overvoltage the second fan which will then fail and possiably ground the 24v rail using the vreg is will just fry and pop if you have a ground fault. I tried it with the fans in series and one fan died just a bad fan and the other fan overvolted and caused a ground fault. nasty atleast if the vreg fails you will know it you will hear a pop then the lvps will go into protect. When the fan failed it made no noise and just went into protect that took time to diagnose. what a pain GRRRR

Plus if you have enough knowledge you can filter the vreg out of the 24v rail so no feedback. just a thought.

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

really this is just one way to do it I have seen so many ways they all work and they all have problems including mine this whole forum is about the joy of tweaking that is why i love the hobby!!! Mr. Green

Joust · Posted: Sat Jan 26, 2008 3:29 pm Post subject:

fireanimal · Joined: 17 Jul 2007 Posts: 231 Location: Stayner, ON

If you want to regulate 24 to 12, I would use a switching regulator if anything, they are more efficient then a liner one. I have a switching regulator that I designed, on a PCB and all. It will allow 6-30 VDC input and has dual outputs @ 12 VDC. Max draw is around 1 amp. It is fuse protected as well.

I will if I can get some pics of it, probably a better solution for this type of fan mod.

1031 · Joined: 22 Mar 2006 Posts: 657 Location: Finland

About that two 12v fan in series i must say that when i changet lvps fans (new silenx models->older 120mm models ) i tested that what happens if one fan stops. I stopped other fan and voltage across other didnt raised much (volt or something..) so i connected those series.. Maybe other fans behave different.

Here is how i dropped that -24 volt to lower for tree belly fans
I used 1ohm fusible resistor then 100uF cap and 7915reg. that gives -15 volt, after that there is four 1n4007 diodes series and little two position switch witch selects voltage after two diodes or after four diodes (about -12 & -13,5v)
So i got "summer" position, if room temperature is hot i can run those belly fans little higher voltage.
Actually i got four 12v papst here.. only tree is in marquee, one is waiting that i got inspiration to get marquee down and modify that fan tray for four fans..Btw its really PITA change those fans when projector is ceiling mounted.

Btw. Mine lvps is 10-000-229-02p iss.1

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

now that is a nifty mod looks like fun. looks like you even buffered the voltage very cool

fireanimal · Joined: 17 Jul 2007 Posts: 231 Location: Stayner, ON

Here is a pic of the swithing reg. that I was talking about.

Joust · Posted: Sun Jan 27, 2008 4:37 am Post subject:

Nice little module. what do they go for? I could use a few for various projects.

fireanimal · Joined: 17 Jul 2007 Posts: 231 Location: Stayner, ON

They are small footprint as well aprox. 2"x2". Probably be around $50 each, which is way less than usual price.

voodoo7869 · Joined: 19 Oct 2007 Posts: 193 Location: Chicago, IL USA

that is really nifty hmmm now where to get them?

fireanimal · Joined: 17 Jul 2007 Posts: 231 Location: Stayner, ON

Propritary, designed by myself.

Gino · Posted: Mon Jan 28, 2008 2:09 am Post subject:

are you able to design one for use for the belly fans so that i can use 4 x 12v fans there? i'd buy 2 of those from you and also 2 of the other one you designed for the lvps Smile

fireanimal · Joined: 17 Jul 2007 Posts: 231 Location: Stayner, ON

If I do some testing to ensure the amperage load, the current design will work for 4 fans. The circuit can currently work with up to 2 amp draw with no cooling. Any more than that there would have to be heatsinks installed on some of the components. If you were to tell them amperage rating of the fans that you intend on using that would help.

I belive though that most fans to not draw that much wattage.

Joust · Posted: Mon Jan 28, 2008 3:14 am Post subject:

typical fan is 1/4 amp.
if the thing is ceiling mounted a nice squirrel-cage fan would be best. with good bearings they are quiet. only drawback is they are not small