Mod: Soundcraft Ghost CPS 275 Powersupply Fan Noise

Hi guys,

I would like to mod my CPS 275 Powersupply to make it fanless as its the loudest thing in the studio. Right now it lives in the speaker soffit so lots of room. I can leave the lid of the chassis if I need to add a bigger heatsink. What heatsinks should I use for the regulators, bridge rectifiers, etc?

Here's a pic from a gearslutz thread




Thanks,
Dave

Ummmmm..... There is a HUGE difference between passive cooling and forced air cooling. Pull the model number off the fan and research its CFM, decibels, power, current... etc. I bet you can find a quieter one that flows the same or more

+1 with jwhmca - get a quiet fan.

But I am sympathetic to the "no fans" idea.

If you do go passive, the sink needs to be vertical to generate airflow and the airflow cannot be restricted by the "little holes in the chassis" vent (needs to be open).  Think "smokestacks"

"The rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings".  But it gets complicated with convection (see convection in this http://en.wikipedia.org/wiki/Heat_transfer).  The convective airflow depends upon the heat being generated to drive it.

If you want to do it experimentally measure the heat sink temp near the transistors after some time under load, then change your airflow and do the same thing.

To go convective you probably need to expand the heat sink or possibly add a second heat sink for some of the components (you could remote mount those rectifiers and the TO220 regulators pretty easily).

I tried the silent fan approach. It is still to loud for me. I bugs me... I like the passive idea

I opened her up. So looks like 1 x LM317T, 1 x TL783C, 1 x LM35, 2 x STPS10, 2 x MJ15024 and 2 bridge rectifiers .

Whats a good heatsink for the TO-220, TO-3 and do the bridge rectifiers need a heat sink ?

http://ca.mouser.com/ProductDetail/Aavid-Thermalloy/529802B02500G/?qs=sGAEpiMZZMttgyDkZ5WiusUw%252bQXhbmeCEk%252bB23vakOA%3d

http://ca.mouser.com/ProductDetail/Aavid-Thermalloy/500403B00000G/?qs=sGAEpiMZZMttgyDkZ5Wiui%252b5MbtACYdRXDlXyRX2RRE%3d

Would these work ?

How hot does it get with the fan?

After about half an hour it was running at 50C at idle with the fan. Pretty hot considering so after some web research, I emailed Jim Williams and called Rick from RAL. Nice guys, very informative... I decided to go with the Powerone linear Power Supplies and wire one up.

Found a manual for anyone interested in what this thing puts out.
Max output current
OUTPUTS DC.
Rail Current
+17.5V 5.25A
-17.5V 5.25A
+5V 1A
+48V 0.3A

So really not such a honking supply.

I think you can make it work convectively. 
Just move the TO220 stuff to a big finned heat sink (maybe like the one classicAPI have for their supplies)  take out the fan, turn the supply on it's side so the existing sink is vertical and put holes on both ends of the case so it can vent.

Trench Recordings said:

After about half an hour it was running at 50C at idle with the fan. Pretty hot....

Click to expand...

Hi,
Did you return the top cover of the chassis in the experiment?
It forms the air tunnel from the back to the front thru the heatsink. Usually, the fan is mounted on the heatsink using some rubber standoffs,
what helps in reducing the noise.
Regards,
Milan

Hello, sorry for the necro post but Ive been having the same issue. I finally found this to be the most relavent thread & hate starting new ones when theres already a good thread going.

I’d love to build a whole new linear PSU as mentioned above but its a bit pricey for me right now. Ive found that the Noctua NF-A8 FLX 80mm works amazingly.

I had to drill out the unused holes in the back side of the fan to get the screwdriver through for mounting & couldn't use Noctua’s rubber chassis mounts as the fan mounts directly into the heatsink. I used their corner grommets & should have used a lil silicone grommet between the screw & the fan body but I didnt have anything. Its still extremely quiet. The only time I heard the fan was during testing when I left the fan unplugged to heat up, then plugged it back in. It was a dull hiss w chassis open in front of me; still NOTHING compared to the weedwhacker I pulled out of the thing.

Again, I’d love to build a whole new PSU but for now, this thing works wonders & is completely inaudible during typical use on my 32ch w/ CAL mod.

It’s a cheap alternative. Not sure if quiet fan tech was as good back when this thread was new but this particular fan is a very effective bandaid.

Hope this helps!

———————————————
—————-Update—————-

  Now that its buttoned up & in the rack, the fan is still completely inaudible but when its dead silent in the room, you CAN just barely hear the air passing through the holes in the front of the chassis once the thing gets going. Less than the AC vent but still, just a bit. Absolutely fine for mixing but not perfect in a one room studio like mine w mics & all. Even still, it is a whole HELL of a lot better than what it was before; the old one resonated the rack which this definitely does not. 

  From an annoying whine to a feint whisper for $20; I’d do it all over again twice.