EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: iDandelions on October 08, 2015, 06:13:21 pm

Title: Rigol MSO2072A Power Supply
Post by: iDandelions on October 08, 2015, 06:13:21 pm
The power supply just let go on my MSO2072A. It was just sat on the shelf on standby with no other connection other than the power lead. It's not been used for days. Loud pop and then some magic smoke.  :--

I've removed the power supply and the source of the smoke can be seen. Capacitor C117 is no more. I've removed the associated 2SK3569 transistor and it looks like it has failed. I've ordered a new one but no idea what value capacitor to use. Any suggestions appreciated?

(http://www.dropbox.com/s/rfw5yh6iky81skf/IMG_3135.jpg?raw=1)

Thanks
Title: Re: Rigol MSO2072A Power Supply
Post by: iDandelions on October 09, 2015, 02:09:31 pm
Thanks for the picture, Peter.

I've replaced the cap and transistor but it seems more than those two components have failed. I'm going to try and get a new power supply from Rigol :(

Do you know the voltages/pin-out of the power supply connector? I might try and power up the scope to see if it's ok.
Title: Re: Rigol MSO2072A Power Supply
Post by: SeanB on October 09, 2015, 05:59:31 pm
Standard switching supply. Change the other transistor as well, and check all the low value resistors and diodes connected to the transistor base, along with the high value resistors that provide a start up voltage to the circuit, along with the capacitors there. Basically all on the primary side will need checking. the high value resistors are very prone to flashing over, as they are not really mains rated.
Title: Re: Rigol MSO2072A Power Supply
Post by: wraper on October 10, 2015, 01:00:07 am
When mosfet fails, often driver IC (+some components between them) fails too. Therefore I would suggest to change TEA1750T and check all components which are connected to gate of the mosfet.
Title: Re: Rigol MSO2072A Power Supply
Post by: iDandelions on October 10, 2015, 02:46:10 pm
Thanks to everyone who has posted.

The driver IC has blown (I've removed it and there's a hole in the bottom). The other MOSFET, SPA11N60C3, has also died along with both capacitors and diodes next to the MOSFETs. Some of the other passives and diodes also look suspicious. I've ordered replacement parts for the IC and MOSFETs but as I don't have a circuit diagram/schematic I don't know what the values should be for the other components.

If I can find a circuit diagram I'll attempt a repair otherwise I think I just have to hope Rigol can supply a replacement board.

Thanks for the updated voltages Peter. I'm going to try and power the scope up later.

Thanks again for your help.