Rhys Goodwin's Weblog
I AM the system administrator. Who do I call?
Fibreglass CPU Duct for a Quiet Home Theatre PC
May 20th
New Zealand Freeview has just launched it’s high definition DVB-T TV service and my existing HTPC was nowhere near up to spec for decoding the high def streams. It was also too noisy for a computer that lives in the lounge so it was time for a rebuild. I was pretty excited; this is my first brand new PC in about 10 years the last one was a Pentium 120 when I was still at school! Of course I’ve had plenty of second-hand and hand-me-down gear between then and now.
The two main requirements for the new build were enough power to decode high definition video and quiet enough not to drive me crazy. Quiet means efficient cooling, I.e. good air flow.
I wanted to run the fan at very low RPM while maintaining good air flow across the CPU and video card; the idea is to pull air past the passively cooled video card, though the CPU heat sink and vent it straight out the back of the case.
I could have hacked a duct together with cardboard and tape but that would been just too easy, besides I wanted to try my hand at some fibre-glassing. After much research, trial and error Here are the basic steps I went though.
Materials (Fibre glass bare essentials can be had for about NZ$50)
- Polyester resin
- Methyl ethyl ketone peroxide (MEKP – The catalyst used to harden the resin)
- Fibre glass re-enforcing Chopped strand Matt (CSM)
- Polyvinyl alcohol release agent (Used so you can separate your part from the mold)
- Release wax
- Acetone (For cleaning up)
- Cheap bushes
- Mixing containers
- Latex gloves. (Keep the nasty chemicals from burning your skin, Box of 100 – you have to change them often)
- Stirling sticks
- Respirator mask
- Casting plaster to make the mold (Not used in the end. See trial and error!)
- Wood, plywood, tape, misc tools, sandpaper, etc etc
Thanks goes to NZ Fibreglass. They were very helpful; they sell in small and large quantities and took me though exactly what I needed to get started so if your in Auckland and need fibreglass gear it’s the only place to go check them out at:
http://www.nzfibreglass.co.nz/
1. Make a mold from wood (and masking tape!).
2. Coat the mold with resin and some fibreglass re-enforcing where strength and shape is needed, around the corners and over the masking tape.
3. Sand the resin coated mold very smooth
4. Wax the mold with release wax; about 6 coats, till it’s very shiny.
The guy at the fibreglass shop was very kind and gave me the last of a tin of wax they had in their workshop; saving $30
5. Brush on polyvinyl alcohol release agent. This stuff is great, it forms a sort of plastic bag-like skin so you can release from the mold. It should really be sprayed on evenly with a proper spraygun but this will have to do.
6. Now ready for the first layer of fibreglass. Mix up the polyester resin with the hardener. Soak the resin into the glass with a dabbing action too much brushing and the fibres will start to be dragged around with the brush. The glass should be saturated and become transparent.
The first layer is done!
7.Now the moment of truth; separate the part from the mold?
Note the PVA film has formed a barrier between the resin and the mold.
At this point I’m wondering if the wax was really necessary.
The part released reasonably cleanly
8.Add more re-enforcing and a top coat of very thin glass tissue. (My homemade roller helps get out air bubbles)
9. Clean-up (sand), add holes for top of heat sink
10. Add bottom sections
11. Lots of sanding to get it nice and smooth and ready for painting
12. Into the “spray booth”….
…Prime and paint
13. Done!
Full System Specs
- Motherboard: Intel DP35DP Media series
- CPU: Core2Duo E8400 3.0Ghz 45nm
- RAM: 4GB Crucial
- Video: Passively cooled Nvidia 8600GT (Gigabyte SilentPipe II)
- Hard drive: Seagate 320GB SATA
- Power supply: Enermax liberty 400(watt)
- Case: Lian li PC61 (Big thanks to Chris for this very nice all aluminium case)
- CPU Heatsink: Thermalright Ultra 120 Extreme
- CPU Fan: Yate Loon D12SL-12 (700RPM @5 volts)
- TV Cards:
- Satellite (DVB-S)
- Technisat SkyStar 2 (PCI)
- Technotrend S1500+CI Module (PCI)
- Terrestrial (DVB-T)
- Hauppauge HVR-2200 Hybrid Dual Turner (PCIe)
- Analog
- Hauppauge PVR-150 (PCI)
- Hauppauge HVR-2200 Hybrid Dual Tuner (PCIe)
- Satellite (DVB-S)
SPDIF KeepAlive for Home Theatre PC
May 10th
After building a new Home Theatre PC I’ve discovered that the onboard IDT audio has a problem with the SPDIF output, or at least my Sony receiver has a problem with it! Every time a sound is played it causes the SPDIF input on the receiver to initialise which takes about 500 milliseconds, after the sound has finished the SPDIF goes back to sleep. As a result the first 500ms is lost off every sound that is played; not really a problem if you’re watching a movie but for applications that have little blips as you navigate around these sounds tend to get missed altogether; such is the case in MediaPortal the HTPC application I use.
My old motherboard with Nforce sound didn’t have this problem the SPDIF remained “active” all the time.
After much searching I did find a few other people with the same problem but no solution so I’ve written a small .NET application called SPDIFKeepAlive. It does just that. It sits in the system tray and continuously plays a silent wave file to keep SPDIF port active.
Hope this is helpful for others, leave comments for bugs / feature requests etc
Version History
Version 1.0
- Initial release
Version 1.1
- Added new output options
Version 1.2 (Current Version)
- Fixed auto play on startup
- Added auto-restart option
(.Net 2.0 Required)
Deny yourself access to a Group Policy
Mar 9th
When clicking too fast you accidentally denied “Full Control” to “Authenticated Users” for a Group policy you were working on. Since deny takes precedence over allow the results are that you are now denied the ability edit the GPO at all. This includes editing permissions to remove the blundered Access control entry! In the Group Policy management console it Looks like this:
Components of a Group Policy Object
A GPO is made up of two parts; a set of files in sysvol and an Active Directory object. When correcting GPO permissions you must modify the ACL on the AD object using DSACLS (included in the w2k3 support tools) and the sysvol NTFS permission.
The following dsacls command will remove the offending deny ACE from the ACL, in this case “Authenticated Users” from the AD object. The object is named by the GUID that can be seen on the inaccessible object in the GPMC.
dsacls “cn={3EE757FE-B5A4-4D23-937D-A3AF5G7F0CEA}, cn=Policies, cn=System, dc=wordpress, dc=com“ /R “Authenticated Users”
If successful this command will return a full list of the permissions for the object
Next up you need to remove the deny ACE from the policy’s NTFS folder ACL. Again the GUID of the policy is used to name the folder:
\wordpreessSysvolwordpress.comPolicies{3EE757FE-B5A4-4D23-937D-A3AF5G7F0CEA}
At this point your GPO will be accessible within the GPMC and the permissions will be consistent across AD and Sysvol. All that’s left to do is to add “Authenticated Users” back to the GPO. Do this by editing the GPO with the group policy editor; doing so will apply permission changes to both the AD object object and the Sysvol policy folder.
Just thought this might help someone, not that it’s ever happen to me! ;-p