Lexmark 654dn power supply dead fans on part # 40x4355

[Jluxster]

Hey all,
Working on another failed Lexmark LVPS power supply. The printer gradually had more and more trouble making it to the post screen until finally no power on at all. I'm replacing the two large caps, and the one small 100uf 35V cap that shows a small bulge. That is the only visible cap issue, but I hear a faint fast clicking that tells me caps are probably the issue.

Have a look at this board and let's make predictions about what's wrong with it, I'll post my repair results and we can see what the issue was.

Thanks!

[budm]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

Bad caps may show no sign of bulging but they can have high ESR. It sounds like you have bad startup/running caps (typical small value 47 ~ 56 uF 50V) in the HOT side, they are for filtering the Voltage for the VCC pin of the SMPS IC's.

[Jluxster]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

Hmmm, OK, this board has a ton of 35V and 50V caps on it. Perhaps one of them is the culprit.

[budm]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

ton of Lytics cap?
https://www.badcaps.net/forum/attach...2&d=1564777195
I see C501, C801, but the third one I cannot see in that picture.

[R_J]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

I see that one bulged cap and would bet C106 is also bad

[budm]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

I see that one bulged cap and would bet C106 is also bad

Good eyes!
https://www.badcaps.net/forum/attach...0&d=1564777195
Time to recap as a set.

[CapLeaker]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

replace all caps that are near a heat source. big or small, doesn't matter much.

[Jluxster]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

Well, last night I replaced the bulged cap and the two large caps, and the unit now functions with no problems. Startup and post.

Good prediction in naming the small cap as the likely culprit.

[Jluxster]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

Here are the images after repair.
Thanks for all the posts.

[CapLeaker]

Re: Lexmark 654dn power supply dead fans on part # 40x4355

glad to hear that you got it going again!