Cocoon Culture No.47




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The replacement of the chassis knobs/feet's. :

I removed the crappy plastic knobs from the chassis, and replaced them with shock-absorbing rubber-feet's found on an old refrigerator compressor. I was really lucky here. The mounting kits and everything just clicked right inn.
The results were also satisfactory. The whole cabinet now kind of like float in the air, and is suspended. Vibrations  in the cabinet are dampened. When the CD-ROM spins up the whole thing sways a little, cool. Other benefits are added protection for the HD against shock vibrations from the surroundings. The usefulness of this of course varies with where you live; in a noisy crowded city with passing cars or in a war-zone with falling bombs. Sometimes it's hard to tell the difference.

The construction of the noise box for the hard-drive :

- details to come. further and more targeted insulation. [ work-file ]

An elaboration of the different prototypes of noise traps.
- possibly add some photos of them. (4 different ones sofare)

Testing the system under different CPU clocking/voltage settings.

Note (1) MB clock multiplier set at 1.5 (that is 3.5 for P233-MMX) in all measurements.

Note (2) CPU Fan present on prcessor all the time, even when dissabled. This might have an effect on the air-circulation over the cooling rib. May improve some if removed.

Note (3) : The utillity "CPU Stability Test" v6.0 was used for stabillity testing.

Fan Stability ? Comment
#1 266 75 3.2 ON YES
#2 266 75 3.2 OFF NO System failed after 6 minutes.
#3 266 75 2.9 ON NO ?
#4 266 75 2.8 ON NO ?
#5 210 60 2,8 ON YES Reduction in PSU HF noise.
#6 233 66 2.8 OFF YES
#7 233 66 2.5 OFF NO System Failed on CPU load testing after 4:50 (mm:ss) Using an enlarged cooling rib. Workes OK. sofar on medium/normal load. (50%). Testing started 20:00 ... end ... 21:00. Waterfall running.
#8 233 66 2.5 ON YES Intressting state. Here the Fan actually makes a difference.

Summary : Experimanting with the different settings, showed that the HF PSU noise did change with different settings. I didn't systematically test and record this, but a major improvement was noticed when going from 3.2 Vcore to 2.8 Vcore. The sound was never eliminated permanently at anypoint however. Furthermore the lower power-consumption reduced the PSU cooler fan speed and noise some.


Update on the Hi-Frequency PSU Noise problem.

Searching the net I found a document [ ref.1 ] by Samuel M. Goldwasse, which suggest that the noise stems from the high frequncy coils and capacitors used in the PSU. Based on this information it should be possible to do something about it.

Testing of the Waterfall software cooling utility. (vs. CPU Idle).

All of them worked great. No preferences. Although the shareware edition of CPUIdle (v 5.6) had a more convenient system load meter (LED-like in the sys-tray).

Adding of a separate power-line with switch for the CD-ROM / Floppy drive.

Notes ! Switching power on or off while system is running, may cause som instability. Possibly due to some power-surges or noises, I don't know. I just observerd it. Could add some filter on the swithch in the future to try to solve this minor problem. For the time beeing, I just decide at boot-up wheter I need the devices on that line. And if I find out that I need them when system is running, I take head for that the system migth crash if switched one way or the other.

Creating a tool for locating the noise sources.

Mounted a small plastic tube on a microphone and wrapped the whole thing up with clingfoil and cello-tape. Hope it works.

Other stuff :

  • Further measurements to locate and pinpoint noise hot-spots on HD.
  • Further measurements to locate the noise sources in the PSU.
  • Further measurements to locate the noise sources in the CTR.

Additional attempt and remedies for noise reduction, based on the new information.
HD - The idea is to target the areas making the whining noise ( if they exist that is) and apply special damping or muffling material. The reason for only covering a small area, as opposed to the entire drive, is to allow air contact with drive metal for cooling purposes. Afraid that the heat will build up in the drive and that the damn thing gets to hot and blows up.
I don't even have a complete backup of all my files. I'm on thin ice here.
PSU - Idea is to find some noise absorbing material to swallow the high-pitched noises, or to stop the resonance. One idea is to experiment with some jelly, glue sticky stuff.
[ Glue-gun testing on PSU no.2 etcetera. ]
CTR - Haven't got a clue yet. Maybe go crazy with the gluegun and some marbles. Adding mass and improving stability. <tick tick> Did so. Glued on intuition inside at different spot. Some on grounding shields to make firmer, some on coils and wires. Tighten some screw on the picture-tube (the one holding the print board with components at the end of the tube). Added some marbles. Result : Poor. Not worth the effort.  Didn't manage to wipe the noise out.

Update - The problem with the monitor (as from now refered to as monitor 1) was solved by itself. After anoying me for approximate 2 years, the monitor terminated said good by with a sudden flash. Only a flat horisontal line wisible on the screen. Sendt for repair. Downgraded from 17 " to a 15 " which feels like heaven. See system specefications for details. monitor(2).

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