Rigol DP1308A bulging capacitor problem - Page 1
Forum section: electronics / testgear

author: benst
author_rank: Regular Contributor
timestamp: May 11, 2015, 07:20:51 pm
content: Hello,I opened my Rigol DP1308A to see if I could swap the fan for a less noisy one. As it is only a few years old, I was very disturbed to see a bulging capacitor right next to the connector of the fan. See attached photo. It is a Nichicon 1000 uF 6.3V, so this was very suspect. All the other caps inside look good at first glance. The cap is in parallel to the fan, which is a DC 12V type. To make sure I put it back together and measured the voltage across the cap. Yup, 12.5 V DC. The cap is only 6.3 V!What the f?Did they screw up their QA? If you own one of these, you might want to check this cap and return it under warranty or replace it with a 16 V type.Ben

author: Zbig
author_rank: Frequent Contributor
timestamp: May 11, 2015, 07:34:46 pm
content: Now, that's embarrassing. Makes you immediately wonder what other silly mistakes are there.

author: pascal_sweden
author_rank: Super Contributor
timestamp: May 11, 2015, 08:05:39 pm
content: Maybe that's why it is obsolete now. See picture.BTW: Never believe Marketing

author: taylor12
author_rank: Contributor
timestamp: May 11, 2015, 08:09:55 pm
content: How long do you think the cap would last before it would buldge? 2-4 hours of run time?

author: benst
author_rank: Regular Contributor
timestamp: May 11, 2015, 08:19:00 pm
content: Also, not impressed by the soldering quality. Just look at that LM358. Must have been reworked.I have had this power supply for about 2.5 years now. It is not my only one, but it has certainly been 'on' for more than a few hours. I don't have this size cap lying around so I'm ordering a 1000 uF 16 V (and 105 deg while we're at it). I'll measure the old one, see what kind of ESR it has...Ben

author: SeanB
author_rank: Super Contributor
timestamp: May 11, 2015, 08:29:02 pm
content: Could run for quite a while if the fan is speed controlled, and rarely went above 8V. Most electrolytics will withstand a small overvoltage for a while, especially the lower voltage ones. 12V would probably have taken 50 hours to kill it.Wonder iF I should stick a Fakichon 6V across a current limited 12V rail and see what happens.

author: benst
author_rank: Regular Contributor
timestamp: May 11, 2015, 08:31:11 pm
content: Quote from: pascal_sweden on May 11, 2015, 08:05:39 pmGood one! I guess the 'clean ripple and noise' is what's coming out of the fan. Especially the noise.Ben

author: benst
author_rank: Regular Contributor
timestamp: May 11, 2015, 08:32:41 pm
content: Quote from: SeanB on May 11, 2015, 08:29:02 pmI don't think it is speed controlled. Always runs full tilt. I measured the DC V across the fan while the outputs were idle. Even then it was 12.5 V.Ben

author: benst
author_rank: Regular Contributor
timestamp: May 11, 2015, 08:34:40 pm
content: And maybe the fact that is is a Nichicon is the reason it didn't blow up all this time? Maybe they have a bit more margin.Ben

author: benst
author_rank: Regular Contributor
timestamp: May 12, 2015, 11:48:28 am
content: I measured the cap, and it was around 690 uF, so that is way off. ESR is about 0.18 ohm which really surprises me, the way it looks...Ben