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**momaka** · 08-24-2020, 11:05 AM

Re: Wise Wing F199 19'' LCD monitor - recapped

So all in all, I figured the recap and modding done on the monitor at this point felt complete enough for putting it into service. The monitor just needed a stand. I've been keeping an eye for one on Craigslist throughout the years, but never found one that was compatible and/or cheap/free or close by… so I made my own with scrap wood:

A little basic, but it works.

I upgraded the monitor on my parents' desktop machine (the old one was a 17” Dell) - good enough for the occasional use they put it through (mostly just when they need to print something.)

The monitor worked nice and dandy until I came to do some SW upgrading and maintenance on their desktop one day. As I was using the PC, I noticed there were wavy diagonal lines running across the screen. Reading through posts on BCN suggested this may be a mains cap issue. After all, I didn't change the original primary cap, which was a CapXon KM. And with the PSU still running very hot (despite my attempt at improving the cooling), it didn't go past me that the main cap could be bad. So I tore up the monitor and found this:

Ah crud!

Desoldered to take a close look and test:

Surprisingly, though, that primary CapXon cap still measured fine on my cap meter.

But then I let it cool down a little. Although still in spec, the ESR did increase slightly:

Unfortunately, I didn't have any 400V caps in stock to replace the CapXon. But there was no way I would put that cruddy CapXon cap back in there. Then it dawned on me

: I live in a country with 120V AC line, so I don't technically need to use a 400V. A 200V cap would work just as well, provided I never move this monitor overseas or somewhere with 220/230/240V AC. With that in mind, I took a look through my junk bins, and found this good old Panasonic TSNH cap, rated for 200V and 150 uF.
https://www.badcaps.net/forum/attach...1&d=1598288510
And it's still in spec

, despite coming from a dumpster-picked early 90's Panasonic TV that was smashed to pieces. I suppose it's never a bad idea to collect PCB boards from old CRT TVs - they always have a ton of useful components.

Getting the cap soldered to the PSU board was not the hardest part.

However, putting the metal PSU cover back on the monitor wasn't quite so possible, because the “new” Panasonic primary cap could not fit in any direction without getting in the way of the metal PSU cover. Seeing that I already had drilled ugly holes through the cover, I figured why not take it

all the way.

And while at it, I also widened the holes on the bottom part of the metal case for even more cooling.

Then I slapped it back together and tested. However, it turned out the wavy diagonal shadow noise on the picture perhaps wasn't caused by the main cap after all, because it was present even with the new primary cap. To isolate the issue further, I tested with another monitor and saw the same wavy shadows. I know the VGA cable (yes, I'm still using analog cables

) is not a cheapo, as it came with the original Dell 17” monitor. So the noise is likely originating from somewhere else (possibly even the PC itself.) Of course, I'm still glad I changed that primary CapXon cap, as it would likely have died in the least expected time and probably ruined the PSU (caps with crud like that often fail open-circuit, as the crud is actually from the terminal lead getting eaten away by the electrolyte and loosing connection to the cap's foil layers.)

With all that being said and done, my suggestion to everyone is to avoid buying cheap monitors. If this monitor is to serve as an example, you can see that bad caps were not the only issue here. Bad thermals/cooling will ruin any cap over time - even the good brands. Also, the picture on the Chunghwa TFT is not so great either - it exhibits mildly compressed colors (though not as bad as Chi Mei LCDs) that I couldn't quite fix through the menu options, no matter how much I turned up/down the color gains and contrast. Even more amusing is the “water colors” effect about 3-4 mm into the corners of the screen. From what I read, this is just a fault of the TFT. It tends to get more pronounced as the monitor warms up. Nothing too bothersome, though.

In any case, this was still a fun repair with some interesting challenges, so I have no regrets about the time I spend fixing this monitor. Hope you enjoyed the read too.

Also, a final word about the recap I did with the Panasonic FM caps: these were often the recommended caps to go to by default by many members here on BCN. However, I'd like to note that it's still a good idea to check the spec sheet of the original caps and maybe try to get replacement caps closer to their spec. In my case, the Panny FM caps had way lower ESR/impedance than the CapXon KF caps they replaced. Although not detrimental to the operation of the PSU, the Panny FM caps did cause the PSU to produce a rather audible high-pitched squealing when the monitor was turned Off or in stand-by mode. I've repeated this experiment (where I used caps with ESR much lower than the original) on many other PSUs with flyback design (as is the case with this monitor), and the results were always very similar: PSU would squeal with light or no load. Regulation is OK, but the audible noise can sometimes be bothersome in a very quiet room - at least for those who are a little more sensitive.

So to sum it all up, I acquired the monitor in late 2009, fixed it mid-2010, put it in long-term service in 2015-2016 and didn't touch anything until noticing the wavy shadow noise around 2019, after which I swapped the primary cap in early 2019 and put the monitor in use again.

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Wise Wing F199 19'' LCD monitor - recapped

Wise Wing F199 19'' LCD monitor - recapped

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