ins_anmy@jhunix (Norman Yarvin) (04/25/89)
When I was shopping around for fans, I was told to look for a ball bearing AC fan, as those were the most reliable. The fans I ended up with (yes, I put two of them in -- and am wondering whether to pull one out) were Pamotor model 8506D. These are 110V AC fans with a rating of 36 cfm. They were a bit thicker than the existing fan, so the grate on the inner side of the fans could not be replaced: any dangling wires inside the case should be tied down (existing wires are all tied down). The difference in quality between the new and old fans is apparent: the new fans are all metal construction and weigh about twice as much as the old; they take about a minute and a half (in open air) to spin down after power is removed (the old ones stop very quickly). The two fans in my machine are close enough in frequency that they put out an audible beat (i.e. the sounds go in and out of phase). I have been running my system fairly continuously for about 9 months with these fans. These fans were more expensive ($26/fan) than Radio Shack's AC fans, but they should be worth it. I got my pair from a local distributor (who will probably ship orders COD from the looks of the invoice I have next to me): Almo Electronics 8309B Sherwick Court Jessup, Md 20794-9632 (301) 953-2566 For those just tuning in, the reasons to replace the fan in your Unix PC are the following: 1) The existing fans are very unreliable, and if they fail, your machine will literally melt. 2) The machine, as distributed, runs very hot; the air coming out of my machine is much cooler than that coming out of stock 3b1s (I did a side-by-side comparison). 3) By moving from a DC fan to an AC fan, you reduce the load on the power supply. There is only one disadvantage: your machine will run more loudly. I have accepted this as a necessary consequence of having more airflow. Of course, I accept no responsibility for anything you do to your machine and make no guarantees of the correctness of the information above (what little there was of it) Norman Yarvin (seismo!umcp-cs | allegra!hopkins) !jhunix!ins_anmy "I can't really represent the size of the sun on the blackboard, but this should give you a good idea."
gil@limbic.UUCP (Gil Kloepfer Jr.) (04/29/89)
In article <1567@jhunix.HCF.JHU.EDU> ins_anmy@jhunix (Norman Yarvin) writes: >When I was shopping around for fans, I was told to look for a ball bearing >AC fan, as those were the most reliable. The fans I ended up with (yes, I >put two of them in -- and am wondering whether to pull one out) were Pamotor >model 8506D. These are 110V AC fans with a rating of 36 cfm. They were a >bit thicker than the existing fan, so the grate on the inner side of the >fans could not be replaced: any dangling wires inside the case should be >tied down (existing wires are all tied down). > Norman Yarvin > (seismo!umcp-cs | allegra!hopkins) !jhunix!ins_anmy I agree with Norman that one should replace their DC fans in the 3B1 with an AC fan *before* the fan fails -- ie. as soon as possible. Unfortunately the fan is a necessity for the machine to stay alive. One thing -- although it may seem like a good idea, keeping 2 fans going is unnecessary and not a good idea. First problem is that it tries to suck more air through the case than it was designed for -- thus pulling lots of dust through the floppy drive (and could damage the drive, if not make it unusable until cleaned). Second, there is really nothing on the left side (viewing the machine from the front) that needs to be cooled. One fan is plenty for cooling -- even with 3 expansion boards in the machine. One other side benefit of an AC fan is that they usually get *very* noisy before they actually fail. If your fan is constantly making a rattling noise (an indication that the bearings are failing), the fan is about to break and should be replaced. ------ | Gil Kloepfer, Jr. | ICUS Software Systems/Bowne Management Systems (depending on where I am) | {decuac,boulder,talcott,sbcs}!icus!limbic!gil or gil@icus.islp.ny.us
jallen@uxrd14.UUCP (Jon Allen) (05/01/89)
Maybe the reason for the two fans is a backup. Since the reliability
of the DC fans is reported to be low, maybe they decided to put two in
to save the machine from a meltdown in case one fails. :-)
Jon Allen
ARPA: jallen@acpy01.att.com
UUCP: {backbone!}!att!acpy01!jallenwtm@neoucom.UUCP (Bill Mayhew) (05/02/89)
The fan on the left side (the side where the floppy disk is) doesn't seem like all that swift of an idea. If anything, it assists in sucking dust in through the floppy dirve slot. If the fan on the right poops out, the power supply is probably going to get too hot anyway, as the left fan isn't going to pull a whole lot of air from the right rear of the machine; it'll favor the floppy slot. Threre is thermal protection on the power supply in *my* 3b1, but I suppose that isn't the case for all machines. Now, mind you, repeated short on/off cycles, isn't going to do a whole lot of good for the integrity of the file system as the power supply repeatedly cools and heats. It could also be that the thermal protection doesn't invoke soon enough to prevent deformation of the case due to the heat build-up. I've thought about either using a thermistor probe or an air flow switch and an external controller to cut power when things get out of hand. A termistor would be fairly simple to implent. The termistor could be placed in series with a latch-up relay that would prevent power cycling. It might be possible to select a thermistor and relay that wouldn't need any transistors, etc to drive the relay. If I get anywhere with the project, I'll post the results. I don't think there is enough of a static pressure drop in the Unix PC case to make using an *inexpensive* commercially available pressure sensor practical; one might be able to use a vane air flow switch mounted outside the case with the fan blowing on it. Bill wtm@impulse.UUCP
smikes@hound.UUCP (S.MIKES) (05/06/89)
Bill, Tell you what I did with my second fan. I reversed the direction of air flow by turning the fan around. This creates the effect of an air tunnel; one fan sucks in cool air, the second blows out the warmed air. I used to have thermal problems until I did this. By the way, if you are having thermal problems severe enough to cause your plastic casing to deform, you have a serious fan problem. You should probably replace the fan and make sure that it is always blowing directly on the power supply side. I do a lot of repairs to 7300's and this is a common problem. Usually the fan's main bearing wears out; this can be detected by an unusually noisy fan. If you replace the fan and want a high volume, low power, quiet one, use a Boxer Hi-Fi of comparable power requirements. (Usually available for about $10.00.) Hope this helps, good luck.
rjg@sialis.mn.org (Robert J. Granvin) (05/07/89)
>Tell you what I did with my second fan. I reversed the direction of air >flow by turning the fan around. This creates the effect of an air tunnel; >one fan sucks in cool air, the second blows out the warmed air. I used to >have thermal problems until I did this. By the way, if you are having >thermal problems severe enough to cause your plastic casing to deform, you >have a serious fan problem. You should probably replace the fan and make >sure that it is always blowing directly on the power supply side. [...] Ummm... Again, I'm sure someone will correct me if I'm wrong, but I recall a lot of discussion in the past that described this as a Very Bad Thing To Do. While blowing air directly onto the power supply may seem like a good thing to do, and certainly isn't a bad thing to do, it completely defeats the air-flow design of the 3b1 (7300). The 3b1 has grills along the front, side and top right which sucks outside air into the machine, and blows it out through the right side fan. The effect is that all major components of the machine: motherboard, RAM, drive, floppy _and_ power supply are cooled adequately. As a matter of fact, covering the top right vents has, in numerous occasions, resulted in warped casing from overheat of the power supply. That much alteration in the air flow is Very Bad, and if you're seeing that kind of problem, check your vents. (Some people have been surprised to find that there are indeed vents on the top of the machine, even though it looks like there should be. NEVER cover these!) Reversing the fan to blow _into_ the machine may keep the power supply happy, but the rest of the airflow won't operate the same. Air will stagnate and escape through a different path, and the air, being forced to escape through a wider area, will cause the airflow to actually diminish. The other components of the machine will not only see less airflow, but will have to contend with the air heating from the air that blows across the power supply. This of course is for the one fan method of 3b1 cooling... How this actually interacts with two fans, one blowing in, one blowing out, is a different matter, but I would suspect that the airflow, especially at the front of the machine would be at least as bad, since there would already be a high amount of air in the machine, not allowing air to enter from the front. Has anyone actually determined what would happen in this case? -- ________Robert J. Granvin________ INTERNET: rjg@sialis.mn.org ____National Computer Systems____ CONFUSED: rjg%sialis.mn.org@shamash.cdc.com __National Information Services__ UUCP: ...uunet!rosevax!sialis!rjg
gmark@ihlpf.ATT.COM (Stewart) (05/08/89)
In article <3053@hound.UUCP>, smikes@hound.UUCP (S.MIKES) writes: > > Tell you what I did with my second fan. I reversed the direction of air > flow by turning the fan around. This creates the effect of an air tunnel; AND, so as to help with the issue of dust being blown into the drive, I put a foam filter in front of the fan. The unit I got was from Radio Shack, and a bit thinner than the stock unit, so the filter fit fine. Soon as you see dust on the filter, vacuum it. Now everybody's happy. > If you replace the fan and want a high volume, low power, quiet one, use a > Boxer Hi-Fi of comparable power requirements. (Usually available for about > $10.00.) What is a "Boxer Hi-Fi"? TIA. - Mark G. Mark Stewart ATT_BTL, Naperville, Ill. ix1g266 ihlpq!gms (312)979-0914
smikes@hound.UUCP (S.MIKES) (05/10/89)
I know it may not be recommended, and it may even be defeating the cooling design of the 7300, but nevertheless, I reversed the fan in mine 3 years ago and it still runs fine with no side effects today. I have not had to replace any component in my machine and it stays up 24 hours a day, every day. Maybe I'm just lucky? Steve
smikes@hound.UUCP (S.MIKES) (05/10/89)
In article <8434@ihlpf.ATT.COM>, gmark@ihlpf.ATT.COM (Stewart) writes: > > What is a "Boxer Hi-Fi"? > This is a brand name and model of a very high performance and virtually silent fan. You should be able to get these from any decent electronics store. They are also used to cool professional audio equipment, as in recording studios. Steve
dca@toylnd.UUCP (David C. Albrecht) (05/10/89)
In article <1611@neoucom.UUCP>, wtm@neoucom.UUCP (Bill Mayhew) writes: > > I've thought about either using a thermistor probe or an air flow > switch and an external controller to cut power when things get out > of hand. A termistor would be fairly simple to implent. The > termistor could be placed in series with a latch-up relay that > would prevent power cycling. It might be possible to select a > thermistor and relay that wouldn't need any transistors, etc to > drive the relay. If I get anywhere with the project, I'll post the > results. I don't think there is enough of a static pressure drop > in the Unix PC case to make using an *inexpensive* commercially > available pressure sensor practical; one might be able to use a > vane air flow switch mounted outside the case with the fan blowing > on it. > I considered replacing the DC fan in my 3b1 with an AC one until I did a conversion job on my girlfriends 7300 to full height and at the same time did a refit of the two DC fans two one AC fan for additional 12v capability. The AC fan was not only louder it also had louder vibration modes in the case which I wasn't really able to figure out how to completely damp. I'm not too keen on loud fans to begin with, buzzing cases are right out. I figured if I really want to protect my 3b1 from melting down what might do the trick is a thermal fuse in line with the AC supply (Radio Shack has a 139 degree C and 226 degree C model). Now, 139 degrees C is pretty hot but if I can mount it somewhere appropriate it would probably do the trick. The only other problem other than choice of mounting location is how to attach to it since it comes with wire leads and it might be difficult to solder to without blowing it. However it gets done, though, its likely it will require case disassembly and a little replacement work should it blow. Since this should be a fail safe device an awkward to replace component doesn't seem to be as bad an idea as it might be otherwise. David Albrecht
jep@oink.UUCP (James E. Prior) (05/10/89)
In article <3059@hound.UUCP> smikes@hound.UUCP (S.MIKES) writes: >In article <8434@ihlpf.ATT.COM>, gmark@ihlpf.ATT.COM (Stewart) writes: >> What is a "Boxer Hi-Fi"? >This is a brand name and model of a very high performance and virtually >silent fan. ^^^^^^^^^ ||||||||| I'm a big fan :-) of quiet fans. But, I'm suspicious of any claim using the word virtually. Virtually silent means that it makes noise anyways. How quiet is it? dB? I've heard a great many fans, and none of them is quiet enough to please me. I, and I expect many others are interested in quiet fans, and would like to know more about the "Boxer Hi-Fi". -- Jim Prior jep@oink osu-cis!n8emr!oink!jep N8KSM
gwr@nz8r.UUCP (Gregory W. Ratcliff) (05/11/89)
Ok Gang here it is... Want to make you unixpc create less noise.
As it turns out the leading edge of the fan blades on the
unix pc (normal fans) pass VERY close to the plastic grate.
This allows the noise to come into the room rather than going
out the inside (honest) I noticed a very SIGNIFICANT decrease
in noise level just by making a box for the outlet holes and
taping it in place. Try it, it takes about 5 minutes. Mine
is perfectly square, made from old punch cards and duct tape.
(its on the back, it doesn't need to be beautiful) And it
really really works.
Let us know if you try it, and like it.
gwr
--
Gregory W. Ratcliff, {osu-cis}n8emr!uncle!nz8r!gwr
ham radio,aviation,tcp-ipsmikes@hound.UUCP (S.MIKES) (05/13/89)
In article <20@oink.UUCP>, jep@oink.UUCP (James E. Prior) writes: > I'm a big fan :-) of quiet fans. But, I'm suspicious of any claim > using the word virtually. > > I, and I expect many others are interested in quiet fans, and would > like to know more about the "Boxer Hi-Fi". Jim, Boxer Hi-Fi fans are manufactured by the Boxer Fan Company [Boxer, Corp.]; they are the originators of the small square cooling fans we all love to hate. The Hi-Fi is their quietest model and is designed for use in home audio equipment and cabinets. At two feet you can't hear it in a quiet room, unless you are a bat or an elephant. (Let's just say it's QUIET!) It's output is between 70-110 CFM and < 30 dBa; it is an AC fan. You should look in your local yellow pages under stereos/hi-fi and try to find a dealer who does custom installations/repairs, they are likely to carry the fan. Also, most *good* electronics supply houses may carry the item as well. Last time I got one they were about $22.00. Steve [The opinions expressed herein are mine, not those of my employer.]