Viewsonic VW2010wb doesn't start

[blast32]

Hello,
I have an Viewsonic VW2010wb-EU (Modell No. VS11674). If I connect it to 230V-net only the LED lights orange (duo-LED, amber and yellow lights). It doesn't react on any key. So the light is permanantly on.
The caps of the powersupply was swollen. The transistor Q5 and the stepup-controller U6 are realy hot. The PC recognize the display correct.

I have done the following things to repair it:
-change all caps of the powersupply (see picture, same capacity and voltage, low esr type, bought from local seller, i don't know which brand they are) -> powersupply seems to work ok now
-change of the transistor Q5 -> no effekt
-provide the 5V power over an external powersupply -> the same error as befor
-disconnect the controllsignals for backlight an provide an external one -> the backlight works fine
-messured the voltage on the crystal-pins -> oscillates at 14Mhz
-messured the Signal of the keys -> they are ok; high if unpressed an low if pressed

I do not know what I shoud do now. The schematics in the servicemanual I have are not complete. The part about U6 an some else are missing.
Has anyone has an idea what the problem could be?
Or has anyone the missing part of the schematic?

Hier the Voltage that i messured at some (in my opinion) intersting testpoints. I used my oscilloscope, so the absolute precesision is about 100mV. If you need an precise value of a testpoint I can messure it again with my digital multimeter (precision about 10mV).

5V Powersupply: 5.14Vdc 30mVac
3V3S1: 3.36Vdc 6mVac
VDDC_1V8: 1.83Vdc 4mVac
V33_1: 3.56Vdc 4mVac (even though its named V33 a 3.5V LDO is used; in the schematic too)
VLCD5V1: 5.01Vdc 50mVac
RST: max. 50mV (highest peak)
All the voltages are messured against GND (see picture).

Thank you for help.
I'm sorry about me bad english, its not my native language. I hope you will forgive me.
Sebastian

[selldoor]

Re: Viewsonic VW2010wb doesn't start

Hi problem here is I suspect you know more about this than I do
I am not sure about this:
"-disconnect the controllsignals for backlight an provide an external one -> the backlight works fine" Do you mean an external 3v BLON signal or do you mean
you used an external inverter to test the bulbs
or something else?

EDIT
Also meant to ask if the set was yours when it started to fault and what were the symptoms
have you ever seen it working?

[blast32]

Re: Viewsonic VW2010wb doesn't start

Hello,
thanks for your reply.

No, I get the unit defective. So I never seen it working. The owner said there were no fault befor. From one day to another the device failed.

There are 2 Datasignals from the Control-IC to the powersupply. Both are to control the backlight, one activates the inverter, the other is for brightnesscontroll. I have disconnected both lines from the powersupply. Then I have connected two signales from an external supply to activate the backlight manually. The CCLF was connected to the original powersupply. I wanted to test whether the CCLF or the inverter is broken.

[selldoor]

Re: Viewsonic VW2010wb doesn't start

Ok so with it connected up can you just check if there is any voltage at all on the two
pins as it is powered on- are they named BLON and DIM or are they unmarked?

[selldoor]

Re: Viewsonic VW2010wb doesn't start

I think see them now labeled on the main board in a box BL_EN1 and BL_ADJ1

[blast32]

Re: Viewsonic VW2010wb doesn't start

They are marked. In FSP043-...pdf they are on page 2 in sector D1 and named "DBRT" and "On/Off".
The servicemanual shows the Pins on page 44 and named the signals BKLT_ADJ and BKLT_EN. The voltagelevel on both Pins is 0V. I think the controll-IC doesn't work korrekt and so the Transistorbases (service manual p. 44) of Q1 and Q2 were tied high about the pullup-resistor RA4 (service manual p. 47).
But I'm not shure about the IC since the osscilator works korrekt.

[selldoor]

Re: Viewsonic VW2010wb doesn't start

Is the small white fuse F1 good

[blast32]

Re: Viewsonic VW2010wb doesn't start

Yes, all fuses are good.

[selldoor]

Re: Viewsonic VW2010wb doesn't start

When the backlights are working using the external signals is there a picture on screen -or does the menu work.


Can you do a close up pic of the area or Q5 and U6 and can you post the part numbers

[blast32]

Re: Viewsonic VW2010wb doesn't start

Nothing on screen, no menu, no picture.
Here is the areapicture.
U6 is an AAT1164 (datasheet in post 1). Q5 is an MMBT4403 pnp-transistor.
I dont think that the regulatorcircuit itself is broken. Either the Load is shorted or one of the externel components of the switching regulator. But I'm not shure. I have no schematics about this part.

The Board is part of the LCD panel. I have found a datasheet, no schematics. The only interissting page here is page 10. It shows the Functional Block Diagram. I think the DC/DC converter in the lower right corner of the PCBA is U6.
The panel is an AUO M201SP01 V0.

[selldoor]

Re: Viewsonic VW2010wb doesn't start

I dont think I can help much, next thing would be to test everything on the board!!! . Start in the area getting hot check that big Diode D5 ,may have gone leaky then the other small diodes. Next area would be Q1 and Q2.
Keep updating and someone may see it who has worked on one before.

[budm]

Re: Viewsonic VW2010wb doesn't start

If you look at the application note page 2 of the ATT1164, you will see the two transistors Q1 and Q2 for generating the Vout2 and Vout3. I believe that Q5 and Q6 on your board are equivalent to Q1 and Q2 in the app notes.
So you need to see if the Vout2 and Vout3 as shown in the app note has low resistance (or shorted load that cause the IC and the transistor to over heat). You should trace out the connections which is more likely to be about the same as shown in the app notes.

[budm]

Re: Viewsonic VW2010wb doesn't start

BTW, this is the application circuit. You can also see 3 diodes and two transistors on your board in that section of the board.

[lexwalker]

Re: Viewsonic VW2010wb doesn't start

Nothing on screen, no menu, no picture.

More detailed description would be more helpful. When you mentioned no picture, is that a white screen or black screen? Does the monitor respond to the front bezel/panel on and off button? In other words, does the power indicator LED respond properly (when using the on/off button)?

[blast32]

Re: Viewsonic VW2010wb doesn't start

Tomorrow I'll check the voltageoutput of U6 for a shorted load. I was hoping someone have schematics for this part.

Hello,
It doesn't react on any key. So the light is permanantly on.

The screen is black. Or better I think its off.

[lexwalker]

Re: Viewsonic VW2010wb doesn't start

Tomorrow I'll check the voltageoutput of U6 for a shorted load. I was hoping someone have schematics for this part.

The screen is black. Or better I think its off.

That's does not sound good at all (pretty dire actually). My guess is that the Dscaler part (which contains the MCU) is not working properly, probably firmware corruption (due to possibly those badcaps on the power supply, can look up on "A81SC" problems found Samsung monitors). Seen quite a number of these problems before (always due to Dscaler board failure)..

If the screen is white then that means the backlighting was activated by the MCU (microcontroller) section. And if there are responses to the front panel buttons especially the on and off button then the MCU section is working properly.

However yours is black which means the backlighting was never activated (in response to a video signal) plus no response to any of the front panel control buttons (including on and off, if not mistaken) all of which points the fault to the MCU (microcontroller) side...

[blast32]

Re: Viewsonic VW2010wb doesn't start

OK, I identified the outputs of u6 and checked them for a shorted load. Nothing. The voltage looks also good. My next and probably last try is to exchange the flashmemory (U8). Unfortunately I have no device for programming yet. But it shouldn't be hard to develop one. I found the firmware online in a russian forum.
But this will now probably take a while.

[blast32]

Re: Viewsonic VW2010wb doesn't start

It lives!
The last 12 hours I spent in developing a flashtool for readout and reprogramm U8.
At first I have seen that the vendor used an ps25lv010 instead of an sst25lv010. The difference is an reduced commandset. But this is not really a problem. I have read it out and found out that the first about 300 bytes were zero. After I reprogrammed it with the new firmware it was time for a test.

The controls works fine, the backlight turns on and I see a picture.

But the repair is not ready.
The picture isn't clear. I don't know how to explain it. It seems like a weaker version of the picture left and right next to the original picture. The black is also not black, its a grey. So text is difficult to read.
But the Menu is absolutely clear. The Signal was connected over VGA. Unfortunately I don't have a device with a DVI-connector, so I can't test a digital signal.

U6 is hot, but I think thats right. Maybe the failure comes from the powersupply. What do you think?

And I found a misstake in my first post (and the title), I can't edit it anymore. It's not a "VW2010wb", it's a "VA2010wb".

[lexwalker]

Re: Viewsonic VW2010wb doesn't start

It lives! The last 12 hours I spent in developing a flashtool for readout and reprogramm U8.
At first I have seen that the vendor used an ps25lv010 instead of an sst25lv010. The difference is an reduced commandset. But this is not really a problem. I have read it out and found out that the first about 300 bytes were zero. After I reprogrammed it with the new firmware it was time for a test.

The controls works fine, the backlight turns on and I see a picture.

As I've suspected, possible firmware corruption (probably due to those badcaps causing bad voltages and messing up the EEPROM). Glad you finally revived it, one less monitor for the landfill...

But the repair is not ready.
The picture isn't clear. I don't know how to explain it. It seems like a weaker version of the picture left and right next to the original picture. The black is also not black, its a grey. So text is difficult to read.
But the Menu is absolutely clear. The Signal was connected over VGA. Unfortunately I don't have a device with a DVI-connector, so I can't test a digital signal.

U6 is hot, but I think thats right. Maybe the failure comes from the powersupply. What do you think?

And I found a misstake in my first post (and the title), I can't edit it anymore. It's not a "VW2010wb", it's a "VA2010wb".

That symptom sounds very familiar. And nopes, nothing to do with the power supply at all. You should try getting a DVI cable to verify. As for that fixing that problem, check the ESD protection diodes at the VGA inputs. Quite often appears as 6-legged I.C package, and sometimes they look like 3-legged transistor package . I've dealt with this problem before...

[selldoor]

Re: Viewsonic VW2010wb doesn't start

Well done!
I supose check all cables are back in place
How about trying a factory reset - if we can find one?
Hope it doesnt wreck your eprom!!