A Tale of Two Dead Viewsonic VA720s

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

Depends on which series he sells.

The GE series is slightly better than Panny FM.
The GD series closely matches Rubycon MBZ.
The GC series roughly matches Rubycon MCZ.

From GE 'up' Samxons go:
GE -> GD -> GC -> GA
(There may be other Samxon series that I am not familiar with.)

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[gonzo0815]

Re: A Tale of Two Dead Viewsonic VA720s

If heat is the main problem, i would considering Samxon RS, sure not the greatest ESR, but 7000h endurance rating.
I think they should equal the FC`s in ESr rating.

[bgavin]

Re: A Tale of Two Dead Viewsonic VA720s

Depends on which series he sells.

The GE series is slightly better than Panny FM.
The GD series closely matches Rubycon MBZ.
The GC series roughly matches Rubycon MCZ.

From GE 'up' Samxons go:
GE -> GD -> GC -> GA
(There may be other Samxon series that I am not familiar with.)

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This implies the Samxon GA series is superior to the Rubycon MCZ... I thought the MCZ was as good as it gets...

[davmax]

Re: A Tale of Two Dead Viewsonic VA720s

Yes the GA series is an incredible product line.

Link to data: http://www.samxon.com/PDF/prodPDF_106.pdf

[RJARRRPCGP]

Re: A Tale of Two Dead Viewsonic VA720s

I can't tell is that cap is bad or good! Please get another angle of that cap!

Also, your symptoms sound more like the motherboard is failing to POST.

This can include a damaged processor on the motherboard.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

So I successfully fixed the 2nd Viewsonic, actually a couple of weeks ago...

I went with Panasonic FC from Digikey since Topcat didn't have Samxon in one of the values needed in the correct size. Sadly due to a typo on the order form I ordered the wrong caps for the Elite 470uf 25vs so I ended up only replacing the known bad 1000uf cap, oh well . Here are the finished results.




It's actually an OK display, especially considering how old it is. I think the backlight may be failing however as I've noticed when monitor is cold (low 60s) the backlight doesn't kick in right away, but after about 5-10 mins of warming up it's fine. I assume thats a sign of the florescent light approaching the end of its life?

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

There are various ways it's implemented and I don't remember the specifics.
Basically the initial power-on cycle gives a little extra kick to initially start the tubes.
The caps that didn't get replaced might have something to do with that.
- Or not. Or something else. Or yeah, aged tubes. Hard to say.

Congrats on your progress.
It works! It works!

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[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

This implies the Samxon GA series is superior to the Rubycon MCZ... I thought the MCZ was as good as it gets...

Nichicon HN, Samxon GC, and Chemicon KZJ are all comparable to MCZ with specific can sizes being either slightly better or worse between the models. (Slightly)

Nichicon HZ and Samxon GA are superior to all of the above but usually limited availability and added cost make them not the best choice.

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[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Basically the initial power-on cycle gives a little extra kick to initially start the tubes.
The caps that didn't get replaced might have something to do with that.
- Or not. Or something else. Or yeah, aged tubes. Hard to say.

Yeah, when it's cold it gets an image for split second and then nothing. I can tell it's th backlight because if I can still see the picture If I shine a flashlight on the panel.

I'm just using this as a backup display anyway so I think I'll call it good.

[davmax]

Re: A Tale of Two Dead Viewsonic VA720s

The short burst of backlight is possibly related to an over current trip that is rest when powered off. There is likely excess current that needs to be identified. Usually there are two sets of lights. Disconnect one set at a time, this may locate a particular lamp/inverter problem.

The kick to start the backlights is quite simple. The inverters have a high voltage that is current constrained by a series capacitor. At "switch on" the voltage is high to strike the tubes and then the voltage drops away due to the series reactance of the capacitor.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Thats for the suggestion davmax, that sounds like a good next step. One that I would probably take if this was a nicer/newer monitor but it isn't...

As it is it's fine as backup monitor, it only has startup troubles when it's really cold (sub 60f).