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Electronics => Repair => Topic started by: 460voltclub on December 11, 2022, 07:07:50 pm

Title: A capacitor on a SMPS failed and I don't know the value.
Post by: 460voltclub on December 11, 2022, 07:07:50 pm
The SMPS ran a medical type fluorescent fixture with two tubes. I want to repair this board because I am too cheap to buy another one but I will if I have to.
If I need to get a new ballast how would I choose one.[attachimg=1]
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: tunk on December 11, 2022, 08:15:54 pm
A photo of the back may help.
Do you know how the capacitor looked like? - e.g. like
the green ones on the left or the red-brownish ones?
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: 460voltclub on December 12, 2022, 12:17:52 pm
Thank you for the reply. The capacitor is a brown film cap. I will get a photo today of the back side. It has a lot of surface mount components.
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: jonpaul on December 13, 2022, 01:30:57 am
resonant cap, likely FETS and other parts blown as well.

Replace ballast perhaps $10 or junk fixtures, use LEDS

J
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: 460voltclub on December 13, 2022, 07:21:16 pm
Thank you for your reply. There are several components I need to check and replace.
I have a lot of test equipment in my man cave. My OCD compels me to fix and use original parts and pieces.
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: 460voltclub on December 13, 2022, 07:25:11 pm
Here are photos of the back.
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: MathWizard on December 14, 2022, 05:27:23 am
It looks like a nice mix of easy to solder/desolder parts. IDK these types of SMPS but if the chips on the back have datasheets, you could find the general layout from that. I don't see the labels on those chips. But if you're like me, I just map out the whole circuit in a simulator, as a way to learn them and keep track of it.

To check SMD caps, I have tweezer probes, but it's still very hard to use them without the part going flying. So I just flow the solder, and flip the cap or SMD part up onto 1 pad. Makes checking them 1000x easier, and plus I don't loose them.

My LCR meter can read some little caps in circuit, but not all.
Title: Re: A capacitor on a SMPS failed and I don't know the value.
Post by: 460voltclub on December 14, 2022, 04:17:47 pm
Thank you for your response.
 I purchased a "Smart Tweezer" from a company in Canada. It will read any components in circuit without desoldering.
I don't know how it works but I'm glad I bought it.

If you need to measure a tiny component use masking tape doubled over and stick it to your bench then stick the component to the tape and it will hold the component in place to measure it. The masking tape wont leave any residue.