Neovo f-419 Power but 1 second of picture

[merrik]

Hi Folks.

Hope you will be able to help me with my neovo f-419.

It has just started displaying a blank screen despite showing a green power LED. If i turn it on and off again then the picture flashes on for about a second before disappearing.

Having resurrected an HP and Samsung recently with visibily bad caps i have popped the back off and there are no obvious signs of bloating or leaking.

Before i launch into anything drastic any advice would be greatly appreciated.

Please let me know if you need any pictures or meter readings and i will endeavour to provide them.

Many thanks in advance

Merrik

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

If i turn it on and off again then the picture flashes on for about a second before disappearing.

2 seconds to black can be

a) bad caps
b) bad ccfls
c) bad ccfl wiring
d) bad secondary windings on the inverter transformers

All explained and more starting with post #19 at

https://www.badcaps.net/forum/showthread.php?t=10419

[budm]

Re: Neovo f-419 Power but 1 second of picture

I believe retiredcaps is going to revise the test procedure to rev4 to include this tip,
you may want to try it to see if you have inverter problem or lamp problem.
https://www.badcaps.net/forum/showthread.php?t=19987

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

I believe retiredcaps is going to revise the test procedure to rev4 to include this tip,
you may want to try it to see if you have inverter problem or lamp problem.
https://www.badcaps.net/forum/showthread.php?t=19987

Yes, I will. It is on the "to do" list.

[merrik]

Re: Neovo f-419 Power but 1 second of picture

Hi Folks,

Sorry for not getting back here sooner but family matters put paid to that for a while but that is all sorted now so hopefully i can to trying to fix this monitor.

I have attached some pictures that should hopefully meet the requirements for size etc.

I have replaced all the electrolytics on the main (cream) board apart from C805 as craplins do not stock any this size so i will need to pick one up from RS when i pass next. IIRC this one rarely fails anyway.

I am still getting 2 secs to black although i think it may now be going to standby (orange) a few secs after that too now.

I have not yet replaced any caps on the secondary (green) board but these are next on my list.

I am using a fluke 12 multimeter that does allow me to measure capacitance so is it worth pulling the caps and checking them before replacement?

Have also had a look at the sticky and worked my way through most of it... trnasistors, mosfets etc but any guidance on specific parts to check based on my boards would be greatly appreciated.

Many thanks

G

[selldoor]

Re: Neovo f-419 Power but 1 second of picture

Hi - Not the best soldering job I have seen. Can you do a close up of the area with the 4 mosfets near the top of the picture. I will try and compare it to another picture.
Secondly Caps from maplins are probably not good enough
for this application - they do not have low enough ESR.
May just work but you might have it all to redo in a week or two.

As a first test if you have not already done it, can you check the secondary windings on the Inverter transformers.

They are at T 901 and T902. Power off (for 5 mins)
Meter on Ohms 2000 or autoranging test across the two end pins on each transformer
See here http://lcdparts.net/TransformerDetai...ProductID=2724
Post results as follow

T901
S1-S2 xxxx Ohms
S3-S4 xxxx ohms etc etc

[selldoor]

Re: Neovo f-419 Power but 1 second of picture

Here is a schematic of the power supply

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

I have attached some pictures that should hopefully meet the requirements for size etc.

Well your pics are easily one of the best in terms of focus and clarity so far this year.

[merrik]

Re: Neovo f-419 Power but 1 second of picture

Hi,

I will take a picture of the U950, U920, U960, U930 area when i have some daylight.

Probably right about the caps from craplins although they have conviniently fixed my other monitor (samsung 2232bw) and my wifes (samsung 226bw) in the past.

If you have a suggested RS range i will replace with them if a fix looks feasible.

Readings on:
T901
S1-S2 = 1.044 Kohm
S3-S4 = 0.927 Kohm

T902
S1-S2 = 0.913 Kohm
S2-S4 = 0.917 Kohm

@retiredcaps - thank you for the kind comments

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

Readings on:
T901
S1-S2 = 1.044 Kohm
S3-S4 = 0.927 Kohm

T902
S1-S2 = 0.913 Kohm
S2-S4 = 0.917 Kohm

The readings above suggest T901 S1-S2 is likely bad. One of the windings may have broken.

The rule of thumb is that the readings should be within 3% of each other.

927 x 1.03 = 954.81
1044 x 0.97 = 1012.68

I can't quite make out the part number on the transformer even though the pics are excellent quality. What is the part number? Ebay is might have a replacement?

[merrik]

Re: Neovo f-419 Power but 1 second of picture

numbers are covered by some sort of varnish but read as:

DG100016500
LSEI147A 05196 S

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

DG100016500

No luck on ebay.com for the above. Unless someone else can find an exact replacement, this monitor might be a spare parts monitor.

[Rtech]

Re: Neovo f-419 Power but 1 second of picture

Using the part number EEA-17 as shown on the schematic kindly provided, these are available via Ebay from Hong Kong

[selldoor]

Re: Neovo f-419 Power but 1 second of picture

Thats not great news - they are relatively expensive as Inverter Transformers go. I have been looking to see if there are any similar with the same sort of resistance but it doesnt look that there are. Its not like its a common sort screen either that you could pick up a non working one cheap an salvage a part.

Perhaps take it out carefully and re test.

Slightly off topic
@ retired caps - or anyone who is reading -if it came to the point of abandoning a repair if no transformer was available what might be the effect of adding a 100 ohm resistor to the 3 lower circuits. Brighter lights? Big Bang? Transformer burn-up? - just wondering.

[budm]

Re: Neovo f-419 Power but 1 second of picture

Did you try this board with another set of lamps in another LCD panel?

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

Slightly off topic
@ retired caps - or anyone who is reading -if it came to the point of abandoning a repair if no transformer was available what might be the effect of adding a 100 ohm resistor to the 3 lower circuits. Brighter lights? Big Bang? Transformer burn-up? - just wondering.

Only one person, maybe two, have tried this and reported it working. See below.

https://www.badcaps.net/forum/showth...=resistor+fool

Using a cap to fool the inverter pwm ...

https://www.badcaps.net/forum/showthread.php?t=13713

[selldoor]

Re: Neovo f-419 Power but 1 second of picture

Only one person, maybe two, have tried this and reported it working.

Thanks - I think I have read one of those before - in those cases they are substituting for a broken bulb. I was thinking of balancing the resistances
on a faulty transformer.

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

Thanks - I think I have read one of those before - in those cases they are substituting for a broken bulb. I was thinking of balancing the resistances
on a faulty transformer.

Sorry, I misunderstood. That is what happens with only 4 hours of sleep.

Now I understand what you are getting at. I wouldn't even know how to "insert" the resistor into the windings though.

[retiredcaps]

Re: Neovo f-419 Power but 1 second of picture

I was thinking of balancing the resistances
on a faulty transformer.

I was thinking about this a bit more and I don't think you can do it. The resistance test is a very simple one, but at least it shows that something is wrong with the secondary winding. If there is something wrong, then it should be replaced as it cannot be expected to operate correctly. The winding is supposed to produce very high voltage and made out of very fine wire.

The best analogy that I can think of right now is a car having one tire that is 15 psi because of a slow leak and three others that are 30 psi. I wouldn't recommend lowering the other three good tires to 15 psi to balance out the ride.

We don't talk too much about a ring tester, but these are standalone devices that are a bit more "sophisticated" and find more faults than the resistance tests.

http://www.anatekcorp.com/test%20equipment.htm

[kc8adu]

Re: Neovo f-419 Power but 1 second of picture

i have seen them further apart than that and still work.
look to lamps.
now one that is significantly lower than the rest or open is cause for alarm.
i have never seen a transformer bad that was slightly higher than the others.quite a bit lower or open.