Viewsonic VA2010wb (flashing screen)

[sabre504]

Hi all working on this unit that came in with the screen flashing on and off as the power was cycling up .

Stripped the unit to reveal swollen caps (as suspected )
Power board being an FSP043-2PI01F i replaced all but the 400v with Pany FC and United Chem KY .

When connected up it still cycles on and off ,tested the inv tran secondaries
(1K both sets ) .
On closer inspection of the board there are heat marks between the trans and C24 ,on the underside of the board there are 2 transistors U2 and U3
both are SP8K3 and am getting o/c between pin 3 (S2) and pin 7and 8 (D1)

Am going to replace these with 2x FDS8984 .
There is no picture of the main board as this is part of the screen .

Any input welcome if anyone thinks i have missed something or suggest any other test ?
Thanks

[selldoor]

Re: Viewsonic VA2010wb (flashing screen)

You seem to have it covered - can you test the lamps on anything else? - Do they all appear to come on when it flashes.

Diode by the main board connector looks to have been hot.
Does it need resoldering.

[retiredcaps]

Re: Viewsonic VA2010wb (flashing screen)

There is no picture of the main board as this is part of the screen .

I would still like to see a picture of the overall layout including the main board that is part of the screen. I haven't seen one of those before.

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Checked the diode tests ok so removed and resoldered,
but the resistor at R264 reading 2.8 and should be 2.2 changed .
Still waiting for transistor's ,hopefully arrive tomorrow .

Picture of layout attached as best as i can get

[tom66]

Re: Viewsonic VA2010wb (flashing screen)

Is that cap on the far right a replacement?

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

HI if you mean the one circled in red yes .

Should have been a 10v 470uf but hadnone so i replaced it with a 16v 470uf
hitano low ESR untill order turns up for test purpose.
Have used these before with no problems the monitor i am using now was recapped with all hitano 2 years ago and still running ok .
Maybe not top quality like panny and others but seem ok

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Hi well parts arrived and have only just had the time to fit them .

Still have the flashing screen issue

So borrowed a known working psu and still the same so i have now turned my attention to the screen .

2 regulators on the screen are reading lower ,3.3 only showing 3.2
and the 1.8 only showing 1.7 .

[budm]

Re: Viewsonic VA2010wb (flashing screen)

You have verify that it does not have lamps problem? The regulator voltages do look bad, but make sure the meter is accurate by measuring know good regulator.

[retiredcaps]

Re: Viewsonic VA2010wb (flashing screen)

2 regulators on the screen are reading lower ,3.3 only showing 3.2
and the 1.8 only showing 1.7 .

Refresh my memory of what multimeter you have. Unless it is an analog one, all modern multimeters have at least 1999 counts so you should have at least 2 decimal places in the reading.

There is a huge difference between 1.70 and 1.79.

A voltage regulator with a 1% tolerance is

1.8 x 0.99 = 1.782
1.8 x 1.01 = 1.818

1.70 would be out of tolerance whereas 1.79 would make it.

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Hi yes tested lamps on 2 different inverter units at the start to rule them out (should have put that in o/p)

Will recheck the regs and report exact reading .
I have both digital and analogue meters .

Sourcing the G1084 - 33 reg is proving difficult as it is 5 amp on the spec.

[selldoor]

Re: Viewsonic VA2010wb (flashing screen)

There seem to sources for AP1084 LM1084 TS1084 5A 3.3 though not all seem to be in the correct package. Also try FAN1084 LT1084

[idea007]

Re: Viewsonic VA2010wb (flashing screen)

thank you good job

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Hi well am at a loss now rechecked the readings and they were different again so checked battery in meter (low) so i changed it and tested again .

1084 -33

input 5.21v
output 3.31v

117-18

input 3.33v
output 1.80v

Fuse

5.30v at both ends
All voltages steady with no fluctuation.

So the problem could be in the main chip ?

[retiredcaps]

Re: Viewsonic VA2010wb (flashing screen)

Hi well am at a loss now rechecked the readings and they were different again so checked battery in meter (low) so i changed it and tested again .

Some multimeters are terrible at not showing the low battery symbol and thus give false readings.

So the problem could be in the main chip ?

What about U3? You don't have reading for that regulator?

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Hi retiredcaps thanks i had missed that one .

So busy concentrating on the power side i had overlooked it so will check that one later when i get home.

If i get no joy then complete stripdown and start from scratch

[retiredcaps]

Re: Viewsonic VA2010wb (flashing screen)

Hi retiredcaps thanks i had missed that one .

That is always why I ask for clear focused pictures even from regulars.

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

Hi there is no power getting to U3 .
Getting 5.2v at zd1 but nothing coming through now to try to track the power flow .

[budm]

Re: Viewsonic VA2010wb (flashing screen)

Are you getting voltage at the pad labeled with V33_1 by the U3 INput pin?

[sabre504]

Re: Viewsonic VA2010wb (flashing screen)

No no voltage at that point

[budm]

Re: Viewsonic VA2010wb (flashing screen)

I wonder if that V33_1 pad is directly connected to the round inductor L1 just above it, can you find out?