Viewsonic VA2010 Power Board

[Fly_Boy_Rez]

Hey folks,

My borther in law had this monitor working fine for him till recently when the screen wouldn't come on unless he toggled the power switch for a very long time. The green power light will come on but other than that no sign of activity. And to check if it's a dodgy backlight I've shone a torch on the screen to see if I can see any sign of life but no joy so far. I said I'd have a look but being a mechanical engineer rather than an electronics specialist I thought I'd seek some advice here.

A google search led me here so I've signed up to ask a few questions.

I've read through the other thread and having spotted sume capacitors with bulges thougth these must be the offending items and have removed them, ready for replacement. This is the board before I starte removing capacitors:-







However as a check I've tested them with my simple digital multimeter, by first shorting them and then measuring the resistance across the leads on a high ohm setting. The resistance starts off very low and then slowly climbs for all of the caps. From what I gather this is the behaviour f a good capacitor, bulging notwithstanding.

I'm tempted to replace the caps regardless... but likely success rate? Who knows. Anyhoo, thought I'd share and if possible gather some of your knowledge and wisdom.

Thanks for reading!

Rez

[japlytic]

Re: Viewsonic VA2010 Power Board

Welcome, Fly_Boy_Rez!

What are the series markings on the Taicon and CapXon (e.g. HD, KM etc.) electrolytics?
Try replacing all electrolytics except for the 400V unit; if it works, replace the 400V unit if you want.
My preferred replacements are Nippon Chemi-Con KY Series (as my avatar shows), or if you can get them, Nippon Chemi-Con KZM.
I seem to be losing faith in Taicon units for low-ESR applications since seeing the photo of the power supply board...

[yyonline]

Re: Viewsonic VA2010 Power Board

Ooh - I just repaired that exact power board. It's downstairs on the workbench now. I looked up all the specs and found matches for all the caps. I'll take a look tomorrow evening and get you a list.

Edit: I spoke too soon! I repaired a similar board, but it is not identical.

So, as japlytic mentioned, you'll need to get the series information for each capacitor. I see you already listed the voltage and capacitance of each. That's a great start, but a bit more information is needed to determine the correct replacements.

C114 - This is Capxon KM series. It is marked KM 105°C. The other Capxon capacitors will be similarly marked to find the series. C114 is the primary filter cap, which rarely fails.

C24 - This is Taicon HD series. It is marked 105°C(HD)P. The other Taicons should be similarly marked to find the series. According to Taicon, Taicon HD is equivalent to Nichicon HD:

http://translate.google.com/translat...6prmd%3Divnsfd

So...C24 can be replaced with any HD equivalent: Nichicon HD, UCC KZE, Rubycon ZL, Sanyo WX. These all have the same specs as the original, but with higher reliability. Panasonic FM is widely available and would be a slight upgrade from the original.

As for the others - get the series info.

Edit #2: My very similar board failed to work even after changing the caps. I had to replace the inverter transformer and it fired right up. It looks like it uses the same transformer as my board, so I can share a link for the replacement transformer if it comes to that point.

[Fly_Boy_Rez]

Re: Viewsonic VA2010 Power Board

Thanks for your swift replies folks!

Here are the rest of the markings:-

C114 = KM 105ºC, C644 Vent (CapXon)

C263
C261
C24 = 0643 (M), 105ºC(HD)P (Taicon)

C244
C241 = KF 105ºC, C644, Vent (CapXon)

C242 = KF 105ºC, C644, Vent (CapXon)

C123 = C643 (M), 105ºC (PW)P, (Taicon)

Not sure which bit is the Inverter Transformer though...

Thanks again!

Rez

[PCBONEZ]

Re: Viewsonic VA2010 Power Board

Taicon is affiliated with Nichicon. [Or was anyway.]
They are not the same quality but then the series name is the same so is the data in the data sheets.

Look in the data sheets for the caps of concern.
Find the 'ripple' and the 'ESR' [Impedance @ 20°C and 100kHz]

Your replacements should have the same or more for ripple.
Your replacements should have the same or less for ESR.
[ Note: Within a series the ESR and Ripple change with the can size, not uF or volts. A big cap in a low grade might have better ESR/Ripple specs than a small cap in a higher grade. ]

The CapXon KM are not low ESR so ESR is not shown in the data sheet...
... go by the ripple ... and get low ESR caps anyway because they should have been used there anyway.

Also:
You only want 105°C for replacements. [They last much longer...]
And pay attention to the diameter - so the new ones fit the hole spacing and into the available space. A 12.5mm probably isn't going to go in where an 8mm came out.
.

---
Off the top of my head.

Taicon HD are compatible to Nichicon HD, Chemicon KZE, Rubycon ZL, and Sanyo [now Suncon] WX series'.

Taicon PW are compatible to Nichicon PW and Panasonic FC.
Chemicon KY and Nichicon HE are one step up in grade. [And those comparable to HD are two steps up.]

CapXon KF uses some odd-ball can sizes so you need to look each one up.
Usually Panasonic FM [two steps above HD] is a good choice but sometimes FC is adequate and other times one step better than FM is needed.
.

[PCBONEZ]

Re: Viewsonic VA2010 Power Board

Not sure which bit is the Inverter Transformer though..

Black. - Shaped like a brick. - Bar Code sticker.

[Fly_Boy_Rez]

Re: Viewsonic VA2010 Power Board

Thanks again for the responses... and for helping to ID the Inverter Transformer.

Capacitors I expect are readily available from the likes of RS (in the UK) so long as I can get across the spec's I'm after... but the Inverter Transformer?

Thanks!

Rez

[Fly_Boy_Rez]

Re: Viewsonic VA2010 Power Board

Right then, for the Inverter Transformer, I believe this is the one I'm looking for.

Now, some help in identifying the right capacitors to order from RS.

My Shopping list goes like this:-

1 x 100μF 400v 105ºC KM, C644 Vent (C114)
2 x 1000μF 10v 105ºC KF, C644, Vent (C241 & C244)
3 x 470μF 25v 105ºC 0643 (M), (HD)P (C24, C261 & C263)
1 x 470μF 10v 105ºC KF, C644, Vent (C242)
1 x 22μF 50v 105ºC KF, C644, Vent

The RS online selector talks about ripple currents and quite frankly that means nothing to me... is there anything in the codes I've described that help determine the required ripple current... or do i go for the highest? or Lowest?

Thanks again all!

Rez

[PCBONEZ]

Re: Viewsonic VA2010 Power Board

As I said:

Your replacements should have the same or more for ripple.
Your replacements should have the same or less for ESR.

Try to avoid extreme 'upgrades' with the ESR. [Which means excessively lowering ESR.]
In -some- circuits too low of an ESR can cause problems.
.
There is no such thing as too high of a ripple rating.
The Ripple Current spec is essentially a max current rating.
.
Also, you can safely use caps of a higher voltage rating than original as long as they physically fit.
The voltage rating is a max limit, not a target value.
.

[Fly_Boy_Rez]

Re: Viewsonic VA2010 Power Board

Well folks, Thanks for all your help! Today the replacement caps arrived from RS, have been fitted and voila! The monitor performs beautifully!

The brother in law will now doubt be most pleased and I've learned a lot from you all in the process.

Many thanks once again!

Rez