Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Thats fine,is that both diodes or just the one,fitted and then removed ??

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Both look ok then.Next with the black lead on that link J35, measure the Dc volts on J32,J33 and FS51.

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Thats fine,is that both diodes or just the one,fitted and then removed ??

D31 is reading 404 in circuit (the one with the gum squashed around it) and it is the one that I have not yet removed.

So, should I remove it, just to be sure, and test again?

Imalearner

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Both look ok then.Next with the black lead on that link J35, measure the Dc volts on J32,J33 and FS51.

When I get to do this, should I return (or resolder ) D32 ( and D31 if I have to remove that) back to the board. I mean, should I solder one leg back on, and if so which one, or both?

Also, just curious, the reading that I have got - how do you know what's a 'good' or 'bad' reading on diodes please?

Ta!
imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Diodes in these positions are used to rectify voltage,and simply that means changing an AC voltage to DC.by putting the black lead on the banded end of the diode(which is the negative end), and the red lead on the positive end the diode then allows voltage from the meter to go through the diode but the reading you get is the voltage drop acorss the diode.Reversing the diode must not allow any voltage through,which is why your meter shows a '1'.
So your diodes look fine, return to their original positios, and measure the voltages as requested in post #22.

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Diodes in these positions are used to rectify voltage,and simply that means changing an AC voltage to DC.by putting the black lead on the banded end of the diode(which is the negative end), and the red lead on the positive end the diode then allows voltage from the meter to go through the diode but the reading you get is the voltage drop acorss the diode.Reversing the diode must not allow any voltage through,which is why your meter shows a '1'.
So your diodes look fine, return to their original positios, and measure the voltages as requested in post #22.

Thanks for that explanation Rtech - I will try to digest - Just to remind you though, I only removed one of those diodes - D32

Please confirm whether I should remove D31 from the board and test again, off board so to speak?

Thanks,
Imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Thanks for that explanation Rtech - I will try to digest - Just to remind you though, I only removed one of those diodes - D32

Please confirm whether I should remove D31 from the board and test again, off board so to speak?

Thanks,
Imalearner

No leave it as it is.

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

No leave it as it is.

Thankyou for that confirmation.


Just refering to post 14 ...

"also the two caps near those should be checked and changed to see if they are the cause."

Should I be doing the same check on these as in post 4, as in, power the board - black lead to striped side of cap, red to the other - meter set to Volts AC?

Thanks
Imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

At the moment,just measure the voltages as requested.

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

At the moment,just measure the voltages as requested.

Okay then.

Following instructions here (I'm flying blind ) with the black lead on that link J35, I have measured the DC volts on

J32 = No Reading

J33 = No reading

FS51 = 14.40V to 16.00V

On FS51 the lower reading is only when first powered on, say about 20 seconds, then it peaks at just below or at 16V

Hope this helps?


Imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Thats fine, and shows that it looks as though the inverter side of the unit is fine,and the problem is with the 5volt part of the circuit.The first thing you need to do is replace both C33 and C35,also ensure that L33, has a good solder joint,also do you know if D31 ans D32 have the same part numbers on them ????

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Thats fine, and shows that it looks as though the inverter side of the unit is fine,and the problem is with the 5volt part of the circuit.The first thing you need to do is replace both C33 and C35,also ensure that L33, has a good solder joint,also do you know if D31 ans D32 have the same part numbers on them ????

Good - I have a mission!

Well, er....I have to go and scrounge those replacement parts off a matey, or put them on order, whichever is the quicker.

And.... am I correct in saying that the replacements MUST be the exact same resistance value rating (in this case 6.3 Volts @ 1000 Microfarad) but can be the same or slightly higher voltage rating?

As for the D31, it looks to me like it is different from the D32, as the photograph shows a little information, not obscured by the 'gum' (what's that for?) as 2 7F.

Cheers

Imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Forget 6.3 volts and get 10v,that is not resistance but "DC working voltage" make sure that they are 1000uF(microfarads),when you put them in, ensure they are the correct way around,also resolder that fuse,as the joints do not look good.I was curious ref the diode part codes,but suspect the new caps may well cure the problem

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Forget 6.3 volts and get 10v,that is not resistance but "DC working voltage" make sure that they are 1000uF(microfarads),when you put them in, ensure they are the correct way around,also resolder that fuse,as the joints do not look good.I was curious ref the diode part codes,but suspect the new caps may well cure the problem

Okay, so my local stockist is 6 miles away, and transport is an issue for me right now and although I could order online for possible delivery for Tuesday next week, I might be mistaken but I have done this instead. ( I am also eager to learn and try)

I have 'found' two 16V 1000uF capacitors off a known-working pc motherboard. Anyways, I stripped them off and have tried them on this project. They seemed to come off easy enough and went back on okay too.

I have resoldered fuse (in black box on photograph)- although it's not pretty - I think all my soldering is sufficient on caps too (yellow box).

I checked DC power again on following.

J33 = No reading

J32 = No reading

FS51 = 18.7 Volts initially but decreasing to stable 15.2Volts over say 90 seconds. So that reading appears to have changed from before.


No change to any readings from the pins though.

Hmmmmmmmmmmmmm? Should I have been more patient and ordered new caps? Or is it my soldering? Doubts fill the mind Is it like this for everyone?

Imalearner

[PlainBill]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Nothing wrong with your soldering. I don't believe it's a matter of your source of capacitors.

Normally, it isn't this difficult.

Now, I don't have any excuse for this lapse. A schematic or service manual would have been a big help. For some reason I never thought to look for one.

The service manual is available at Elektrotanya. Well, there are three service manuals there - VA1616W, VA1616W-6 and VA1616W-8. The one for the VA1616W has a very complete theory and troubleshooting procedure, but it's for a different power supply. More later.

Awww, fiddlesticks. NONE of them have the correct power supply schematic.

NOW, this is getting personal. A photograph of the label on the back of the monitor would be useful. There seem to be several different models of VA1616W.

PlainBill

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Nothing wrong with your soldering. I don't believe it's a matter of your source of capacitors.

Normally, it isn't this difficult.

Now, I don't have any excuse for this lapse. A schematic or service manual would have been a big help. For some reason I never thought to look for one.

The service manual is available at Elektrotanya. Well, there are three service manuals there - VA1616W, VA1616W-6 and VA1616W-8. The one for the VA1616W has a very complete theory and troubleshooting procedure, but it's for a different power supply. More later.

Awww, fiddlesticks. NONE of them have the correct power supply schematic.

NOW, this is getting personal. A photograph of the label on the back of the monitor would be useful. There seem to be several different models of VA1616W.

PlainBill

I checked the same three schematics,and this really cannot be that hard,there is very little involved with the 5V cct...back to the board photos methinks !!

[PlainBill]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

I checked the same three schematics,and this really cannot be that hard,there is very little involved with the 5V cct...back to the board photos methinks !!

What I find interesting is the dual opto-couplers.

I do have one suggestion. Check the resistance of the transformer windings. Theory says that if the primary of the transformer is driven you should have output from both 5V and 12V secondaries, as well as the tertiary winding that provides power for the SMPS controller. Since 12V is present, that implies there should be output from the other two windings. Maybe a bad solder joint? Broken winding?

PlainBill

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Yes very confusing.....lets try something simple.Take the fuse out completely,with the meter on DCVolts,Black lead on J35, put the red lead on the end of D32 whch is the one with the 'band' on

[imalearner]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Yes very confusing.....lets try something simple.Take the fuse out completely,with the meter on DCVolts,Black lead on J35, put the red lead on the end of D32 whch is the one with the 'band' on

.....lets try something simple, I like that idea alot.

I have removed fused, (not shown in photograph) but because I am wary of screwing it up, please clarify, should I be putting the red probe on D32 ON the banded end? I thought that this was a 'negative' terminal, as it has the strip on it, or doesn't it matter which end I put it on?

So is my photograph for this test correct, or even relevant, please? I have removed fuse.

Ta
Imalearner

[Rtech]

Re: Viewsonic VA1616W Non Starter, No Lights, Suggestions Please!

Youa re correct.Although the 'Banded' end is negative,,the diode is rectifying the Voltage coming in through the +ve end, so you are right.Lets also add something else.You will notice that after the Voltage goes through the fuse IF and WHEN it is refitted,it goes onto the pins and then up under a resistor RJ32,turns right,and goes to other components.You will notice one of these, which I have marked on the attached...it is marked Z31 but just looks like a Black blob, no matter how I magnify it,,is there a component there, or does it look as though one has burnt out ???????//