Panasonic Microwave. Poping fuse. - Page 1
Forum section: electronics / general

author: PeterG
author_rank: Frequent Contributor
timestamp: April 02, 2013, 01:30:39 am
content: Our Panasonic Microwave oven blew its fuse the other day. It is an old Dimention4 model. The oven powers up fine whith a new fuse but as soon as i start cooking i hear the mot hum loudly and it pops its fuse after a couple of seconds.Could there be a simple fix for his?I would like to repair it if possible as it was built to last and it is a decent size.Regards

author: lowimpedance
author_rank: Super Contributor
timestamp: April 02, 2013, 01:58:51 am
content: So this is not an inverter style, but the good old transformer type then?.Perhaps there is a leakage path from the magnetron heater to the case.Use your meter to check, but be absolutely sure the HV cap is discharged.(although they are supposed to have an internal disharge resistor these do go open cct,thus no longer removing the charge quickly!!).Unfortunately it may well be 'quicker' to get a new oven.LowZedit: forgot to mention, remove the leads to the magnetron before checking for shorts to case

author: oPossum
author_rank: Super Contributor
timestamp: April 02, 2013, 02:28:25 am
content: Bad capacitor in the doubler is a common failure that will behave as you have described.

author: PeterG
author_rank: Frequent Contributor
timestamp: April 02, 2013, 05:14:28 am
content: Many thanks for your help. However, the wife has now decided she needs a new microwave oven. This means the old oven was scrap so i now have a nice heavy MOT to play with.........Regards

author: Psi
author_rank: Super Contributor
timestamp: April 02, 2013, 06:48:29 am
content: Yeah, it was likely a failed capacitor which was shorting the high voltage. I've seen that many times.Be careful with your new MOT, ~1.5kV @ 0.5A is many times more dangerous than the 110/220V mains.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 02, 2013, 06:59:04 am
content: Has Photon been around your place mate?

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 02, 2013, 06:59:48 am
content: Quote from: PeterG on April 02, 2013, 05:14:28 amOr maybe you should invite him 'round.

author: PeterG
author_rank: Frequent Contributor
timestamp: April 02, 2013, 07:07:13 am
content: Quote from: Ed.Kloonk on April 02, 2013, 06:59:04 amPhoton is most welcome to visit ...Regards

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: October 05, 2016, 12:58:06 pm
content: HI, I know this is an old thread but I have the same problem and may be someone can help please.Someone mentioned a faulty capacitor but the it was somewhat unclear.Is this the big capacitor connected to the transformer or a capacitor on the mcu board?Thanks in advance.nico

author: SeanB
author_rank: Super Contributor
timestamp: October 05, 2016, 05:35:31 pm
content: The big capacitor, typical value is between 0.9uF to 1.2uF, it will cause this if it goes short circuit. If it is short circuit replace it and the high voltage diode along with the fuse.If it is blowing the 8-10A fuse in the power side ( typically on the input filter board) then your door switches are more likely the culprit, there are 3 switches there, so arranged that 2 of them close as the door is closed, and the third is there to both provide power to the transformer when closed, and to short out the supply and blow the fuse if the other 2 fail as closed. If so replace all 3 switches, and check the alignment of the door and latch.