Photo and fan mod of a BK Precision 1785B - Page 1
Forum section: electronics / general

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 04:48:55 am
content: After watching EEVblog #8, I also wanted to have a PC controllable PSU from BK Precision, but a linear one. So I bought the1785B. Nice unit, but the fan (NMB 2410ML-04W-B40) kicks in quite fast and is annoyingly loud. So I modded atemperature controlled fan regulatorinto it:The black box in the lower left is the fan regulator, the sensor is the grey blob above the "Burn-in Pass" sticker. Noise is better now!

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 16, 2011, 05:58:01 am
content: Be careful to check temperatures after this mod so you dont burn your power supply

author: saturation
author_rank: Super Contributor
timestamp: December 16, 2011, 11:25:08 am
content: That's a great idea. Are you still using the same noisy fan? What temp did you use as the turn-on for the fan? You can find quieter fans that have the same cfm that run continuously but without the temp control.

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 11:57:33 am
content: Quote from: hacklordsniper on December 16, 2011, 05:58:01 amI measured 36 °C on the heatsink after running a load of 5 V and 1 A for some time.

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 12:00:13 pm
content: Quote from: saturation on December 16, 2011, 11:25:08 amYes.Quote from: saturation on December 16, 2011, 11:25:08 amThe PSU itself turns on the fan. I just made it go slower.Quote from: saturation on December 16, 2011, 11:25:08 amI'm a bit sceptical about this, but I think I'll try this when silencing my Rigol 1052E/1102E.

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 16, 2011, 12:51:28 pm
content: Rigol is proven to whitstand lower airflow

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 12:53:57 pm
content: Quote from: hacklordsniper on December 16, 2011, 12:51:28 pmThe voltage regulator supposedly getting quite hot makes me a bit nervous.

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 16, 2011, 01:12:36 pm
content: Quote from: sonic on December 16, 2011, 12:53:57 pmI did the mod on quite alot of units, nobody complained until now and the oldest one sold is more than year old

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 01:19:19 pm
content: Quote from: hacklordsniper on December 16, 2011, 01:12:36 pmDo you have specifics or a link?

author: saturation
author_rank: Super Contributor
timestamp: December 16, 2011, 02:53:57 pm
content: Look specifically for low noise fans; old cheap ones are noisy, I think the new ones have special bearings to make them quieter. If you reduce the fan speed to make it quieter, you'll reduce the airflow and thus, the rate of cooling. It may help to take temperature readings at full load, with the default full fan speed and see what happens if you change it. Always better to be cool and noisy than hot and quiet.You may have something similar in your country:http://www.acousticpc.com/index_quiet_computer_fans.htmlEnjoy your moddings!Quote from: sonic on December 16, 2011, 12:00:13 pm

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 16, 2011, 05:37:16 pm
content: Quote from: sonic on December 16, 2011, 01:19:19 pmSure, this is the fan i used in all units:Revoltec AirGuardVeli?ina : 60x60x20mmNivo buke: 19.99 dBAProtok zraka: 12.31 CFM / 20.92 m3/hBroj okretaja: 2500 RPMKonektor: 3-Pin MolexRadni napon: 7 V - 12 V DCUlazna struja: 0.08 ALežaj: HysintŽivotni vijek: 50.000 hoursYou can see how it looks herehttp://www.hacklordsniper.com/Arhiva_projekata/Projekt_(16).htmlI posted a english topic here some time ago about it too. With this fan the Ds1052 becomes completly silent

author: sonic
author_rank: Regular Contributor
timestamp: December 16, 2011, 08:03:18 pm
content: Quote from: hacklordsniper on December 16, 2011, 05:37:16 pmThanks, but since I'm a fan of temperature control, I ordered anebm-papst 612 NGMI. I'll report when I have built it in!

author: Unknown
author_rank: Unknown
timestamp: December 16, 2011, 08:53:29 pm
content: If you want to claim that the fan the manufacturer used is too loud, you should also test at its max. operating temperature, not just in an air-conditioned office. Some equipment may be designed for high density rack-mount operation, requiring even more airflow. They may also try to keep the temperature down to reduce drift and noise.There's a fairly strong correlation between air flow and noise for a constant fan size, so two fans of the same size that move the same amount of air tend to be fairly close in noise, at least for the common axial fans. Bearing noise can make a difference, especially if one of them has really bad bearings, but this tends to be fairly minor compared to the turbulence noise. The fan blades an also be adjusted to trade off pressure for air flow. Most of the fan replacements that decrease noise tend to boil down to decreasing air flow.There's a quite good treatment of this topic onSilentPCReview.com. They first try to choose more efficient components to lower the amount of heat they have to get rid of, decrease the impedance the fan sees so more air gets moved at the same speed, increase the internal temperature so the larger temperature gradient allows them to move more heat in the same volume of air, and the last thing is choosing a large, low speed fan with the least bearing noise. You'll also see is that the specs of many fans offered to retail customers tend to be flat-out wrong.

author: sonicj
author_rank: Frequent Contributor
timestamp: December 17, 2011, 10:43:41 pm
content: i did this over a year ago to my rigol. i took before and after dB measurements, but i misplaced them then forgot about it. i'm usually done long before i notice any increase in fan rpm.-sj

author: sonic
author_rank: Regular Contributor
timestamp: June 30, 2013, 03:45:58 pm
content: Quote from: sonic on December 16, 2011, 08:03:18 pmAfter the warranty expired, I finally did it. It's a little bit less loud, but unfortunately it isn't exactly silent yet.