[Repaired (mostly)] Broken Rigol DS1054Z - Blown PSU - Page 1
Forum section: electronics / repair

author: Paciente8159
author_rank: Newbie
timestamp: September 21, 2016, 01:28:29 pm
content: Hi there everyone.I had a freaky accident with my Rigol DS1054Z. I accidentally pulled the probe cables and dragged the scope from the desk to the floor. It dropped with the screen facing down. My home differential protection circuit kicked in so I knew some sort of a short happened in there. The fuse was totally blown. I shacked the scope to listen for any damage and a piece of plastic fell of from inside. So i opend the scope and found that the internal PSU shorted a pin of the big electrolytic cap shorted against the metal cover.I found the broken component, but I need help identifying it (don't know if it is a varistor or a capacitor of some sort) so if someone could help it would be great. I know I should also check the big cap but I have no ESR meter.Any other advice? Should I make this scope a proper funeral after this event??I've attached a picture of the scope inside and signaled the broken component.Thanks in advanced.

author: silverlego3
author_rank: Contributor
timestamp: September 21, 2016, 02:30:48 pm
content: Hard to tell from the picture but it looks like it used to be a ceramic capacitor.

author: Orange
author_rank: Frequent Contributor
timestamp: September 21, 2016, 02:44:14 pm
content: Maybe it is an NTC to limit the rush-in current. if so they usually have values from 5..10 ohms.Does the tear down video of Dave give you a clue ?

author: OE2WHP
author_rank: Regular Contributor
timestamp: September 21, 2016, 02:51:02 pm
content: Here is a picture of how it should look...http://www.experimental-engineering.co.uk/wp-content/uploads/2015/08/IMG_20150821_134257.jpg

author: singapol
author_rank: Frequent Contributor
timestamp: September 21, 2016, 04:36:29 pm
content: The broken component is an NTC.Hope someone with the same model will be kind enough to give you the resistance value. Just be sure to get the right size or diameter, of course you can fit in a bigger one if the hole fits the lead. Replace the big cap and check if other components have failed. The power supply should be repairable and work again.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 21, 2016, 05:03:36 pm
content: One should check the input side rectifier too. Chances are that it is only that poor little NTC that worked as a fuse.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 21, 2016, 05:05:55 pm
content: Quote from: Kleinstein on September 21, 2016, 05:03:36 pmI was just going to post that. Just replace it, even if it measures ok you can be sure it's not what it was before the accident.The cap will be ok.

author: Paciente8159
author_rank: Newbie
timestamp: September 21, 2016, 05:12:48 pm
content: Thanks guys.After reopening scope my suspicions are that itwasthe NTC. The piece of plastic that felt from the had the letters "D-" on it like these.If anyone could supply the correct value/reference it would be sweet.Here is a better picture of what used to be an NTC.There is the back picture of the point of contact too. I clipped the cap pins to give it more room.

author: SeanB
author_rank: Super Contributor
timestamp: September 21, 2016, 05:27:59 pm
content: Just grab the one out of the nearest dead ATX power supply, it will be around 10R cold resistance ( generally) and will work fine there. Also change out that bridge rectifier, it will have had a massive stress event from the single cycle of current that blew the side off the NTC, and the donor PC power supply one likely will still be fine ( normally the caps die on those cheap ones) do is a good fit in item.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 21, 2016, 06:36:11 pm
content: The component is an NTC.It Reads NTC 10D-11.I can't see why it would have shorted even if dropped... Perhaps a nasty angle?

author: Paciente8159
author_rank: Newbie
timestamp: September 21, 2016, 08:39:22 pm
content: Quote from: Assafl on September 21, 2016, 06:36:11 pmThank you Assafl.Has I said the legs on that cap were left too long. Probably they were almost touching the metal frame. The oscillation from the fall was enough to allow an electric arch.Thanks you all. I'll try to fix it and post the results after.

author: bitseeker
author_rank: Super Contributor
timestamp: September 21, 2016, 10:51:15 pm
content: Wow, that was quite a fall to bend the PCB enough to short the filter cap. I guess the leads were pretty long. Hopefully, the screen and encoders on the front panel are still OK.Looking forward to your update once you get the power supply working again.

author: Paciente8159
author_rank: Newbie
timestamp: September 27, 2016, 11:14:06 pm
content: Quote from: Kleinstein on September 21, 2016, 05:03:36 pmYou were right.The bridge rectifier was bad. Actually I could see it in circuit with the DMM.I replaced the original (GBU 408) with a KBL406G salvaged from a dead PC PSU. I got a almost identical NTC (a 10D-9) from a broken laptop transformer.The cap measured 136uF (~-10%) (I don't have an ESR meter to check the cap ESR), so I left it in place.Replaced the fuse and the Rigol is now alive.There is some noise/distortion that changes when I change the DC offset.I haven't changed the 150uF cap. I'll probably order the correct components to see if it fixes the distortion, but giving that the scope is alive I'm happy.