Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

[tom66]

I got this monitor for free. Caps are bad. Does anyone think the caps could cause this problem? The monitor will switch on and display an image but quickly the image goes bad. Or, it won't switch on at all and the power LED blinks. Or sometimes, there is not even a power LED lit up. Should I replace the 220u (smaller one) too? Monitor manufactured in 2005, but has been in garage for a lot of that time.

http://www.youtube.com/watch?v=-DhTFSTRwA8



Interesting thing about this supply. It looks like whoever designed this actually did a good job: the supply has only 5V and 12V rails, and uses 25V caps on the secondary side everywhere. A general rule is a halving in supply voltage increases lifespan by 10x. Unfortunately, the purchasing department decided that "xunda" caps would be good enough, and obviously, they have given up eventually...

Another thing, notice the zener and the fuse. The 6.2V zener protects the 5V rail it seems. So when the supply goes above about 6.2V, the fuse blows, protecting the monitors electronics. Now, on a later revision, here (from this post):



there is no zener. So more cost cutting. The zener is probably less than 1 cent in quantity. The engineer(s) probably wanted to build a reliable device, but management wouldn't let them.

[PlainBill]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

1. With the exception of the 100uF, 450 volt cap, replace ALL the electrolytic caps, even those that appear to be good. I suggest Panasonic FR, FM, or FC series.

2. Don't post pictures inline. They seriously inconvenience those with a slow connection, and annoy the rest of us. Use 'Manage Attachments' instead.

PlainBill

[tom66]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

Okay, sorry about the inline images.

I used 470u 25V United Chemi-Con low ESR caps. These seem to work well, and the monitor is now working... or so I thought. I avoided replacing the 220u as I didn't have that cap at hand. Now it isn't turning on fully. It will switch on but then after a few seconds switch off. The backlight sometimes flickers, which makes me wonder if I have a CCFL problem. (However, flashlight test fails, there is no image.) And it makes a whining sound from inside. I might have to replace the 220u. What do badcaps members think?

[seanc]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

I'm confused, are those pictures of you monitor or not?
Some are bulged in one picture but not the other.

What series of United Chemicon capacitors did you use and where did they come from?
Yes replace the 220uf cap, especially if it is bulging.

[tom66]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

I'm confused, are those pictures of you monitor or not?
Some are bulged in one picture but not the other.

First is my monitor, the second pic is a curiosity from someone else's monitor. Noting that the zener was dropped from a later revision.

What series of United Chemicon capacitors did you use and where did they come from?
Yes replace the 220uf cap, especially if it is bulging.

I need to double check the cap but the 220u is not bulging. I used "KY" type. Datasheet here.

[Th3_uN1Qu3]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

Whining sound = PSU in protection. Replace the 220uF too, if it still won't work, make sure you didn't make any solder bridges.

[tom66]

Re: Xerox monitor, doesn't turn on some times, or turns on and picture goes funky

Whining sound = PSU in protection. Replace the 220uF too, if it still won't work, make sure you didn't make any solder bridges.

The monitor works perfectly if left to stand for a few minutes. Cap problem it seems to me. Maybe the 470u's were enough to keep it stable for a while, but then it died after the 220u drops too low/ESR increases too high due to temperature. I've ordered some Panasonic FC.