AG Neovo F-419 Stuck in powersave mode.

[rash.m2k]

Hi,

I've got AG Neovo F419 TFT thats stuck in powersave mode, as soon as power is plugged into it, the LED should go green, but it stays solid yellow (i.e. as if it's in permanent stand by mode).

I've cracked it up and can't see any leaky/bad caps, however I have done a multimeter test and the resistance of some of the capacitors is 0 (it should be high resistance if the capacitor is not damaged?). All of them are 47j 3KV TDK capacitors (small blue capacitors).

Before I go desoldering them, has anyone else seen this problem/issue before and can provide me with some pointers?

(I'm more of a s/w engineer and we didn't do many electronics courses at uni - but more than capable of understanding anything as long as you explain it a little).

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

Those caps you mentioned are on the inverter. Definitely desolder them and check for resistance again, both on the caps and on the board, they shouldn't read shorted. If they do, the inverter transformers or CCFL wiring could be shorted. Btw, also test resistance in the same spots but with the CCFL connectors unplugged.

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Those caps you mentioned are on the inverter. Definitely desolder them and check for resistance again, both on the caps and on the board, they shouldn't read shorted. If they do, the inverter transformers or CCFL wiring could be shorted. Btw, also test resistance in the same spots but with the CCFL connectors unplugged.

Sorry I meant the display on my multimeter does not change (my bad), it just stays at '0.0L', they are not shorted - but I could do a continuity test that might help.

The LCD contains two boards, the inverter (converts AC 230V to DC?), and the board that drives the LCD, I've completely disconnected the two boards.


Initially this happened once or twice, the LCD would not come on and the yellow light would stay lit, after disconnecting the power and leaving it for a little while it came back on, I used my desktop daily and never had a problem, however this problem re-appeared after I had not used my screen for a few weeks and it's been like this ever since.

Hopefully that provides some backgroud info. Is there any hint of what could be wrong or what to check for?

These two posts have pics of the board:

https://www.badcaps.net/forum/showthread.php?t=14440

and here:

https://www.badcaps.net/forum/showthread.php?t=8782

I'm happy to post more if needed.

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

0L means overload aka resistance larger than meter can measure. Then they're fine. Your symptoms sound very much like bad caps. Replace all electrolytics even if they don't look bloated. Don't miss the small startup cap of the SMPS controller, almost always of a 50v rating, and of a 10, 22 or 47uF value.

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Don't miss the small startup cap of the SMPS controller, almost always of a 50v rating, and of a 10, 22 or 47uF value.

Where would I find these on the board? I've tested every single capacitor I can see, I tested all of the cylinder shaped ones, and all of the blue flat circular ones, and a single small orange one.

The only ones I can test that *seem* to be faulty are the small 47j ones, BTW there are about 8-10 47j 3kv capacitors, and only about 3 or 4 of them do not register on the multimeter.

One final question, the multimeter I have does have markings for measuring farads, do the -ve/+ve terminals make a difference on the blue flat cirular ones? And what should the multimeter show if I switched it to farads and measured one of the small blue capacitors?

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

A capacitance meter ie one that measures farads is useless in SMPS applications, electrolytic capacitors always go bad due to high ESR (equivalent series resistance), their capacitance hardly ever changes.

The 47j capacitors in the inverter should measure 47 picofarads. No good capacitor should ever register on a resistance meter - if it does, it's either bad, or there's a resistor parallel with it.

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

A capacitance meter ie one that measures farads is useless in SMPS applications, electrolytic capacitors always go bad due to high ESR (equivalent series resistance), their capacitance hardly ever changes.

The 47j capacitors in the inverter should measure 47 picofarads. No good capacitor should ever register on a resistance meter - if it does, it's either bad, or there's a resistor parallel with it.

My digital multimeter can also measure farads, there are about 4 ranges which I can select to measure farads. I've ordered some capacitors and I'll replace the 'faulty' ones.

A quick google search led me to someone that said to get an indication of a working capacitor it should register a high resistance? Is that not correct? It seems to make sense because the capacitor is just 2 conductors seperated by an insulator, and thus should have a very high resistance? But not out of range?

The reason I think these are faulty caps is because with ALL the other capacitors the display on my multimeter changes - however with the faulty caps it does not change at all - it just stays at 0L.

I'll try to investigate further once my new caps arrive and report back.

[PlainBill]

Re: AG Neovo F-419 Stuck in powersave mode.

Unless you have an ESR meter, you can't perform a meaningful test on these caps. Before sending you off to replace 23 electrolytic caps (which may not fix the problem), how about performing a few meaningful tests to verify there is a problem?

1. With the monitor disconnected from the computer, plug the monitor in to power. Does the power LED come on in active mode (green or blue)? If it comes on in standby mode (amber), or doesn't come on at all, does it respond when you push the power button? Does the monitor display anything on the screen at any time?

2. If nothing you do will bring the monitor to active mode, it's time to check a few things on the signal card. U10 and U11 are voltage regulators. Use the bare metal around the mounting point in the upper left corner as the ground point. Measure and report the voltages on the three pins of U10 (pin 1 is on the right in the picture) and U11 (pin 1 is toward the top of the picture). What are the part numbers of U10 and U11?

Edit: I see you have gone ahead and ordered new caps. A few points:
1. The replacement caps should be name brand, low ESR caps.
2. You might as well replace all electrolytic caps (all 23 of them) on both the power supply / inverter and the signal card.
3. The reason you aren't seeing any indication on the small blue caps is their capacitance is too low to register. It's a little like concluding a bathroom scale is defective because it doesn't change when a fly lands on it.

PlainBill

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

When the capacitor has a significant capacitance value, the time in which it charges from the voltage presented by your multimeter in resistance measuring mode, is slow enough for you to see on the meter. The cap will show low resistance at first, then climb up till it goes over range.

The amount of current that gets lost due to parallel resistance, among other factors is called leakage current. It is very small compared to the ripple current the capacitor normally faces, and rarely exceeds a few microamps. (1 uA = 0.000001 A) Now, if the leakage current of the capacitor is 1 micro amp at 16 volts, and all of it is due to parallel resistance (which it is not), then the resistance of the capacitor would be 16 megohms. This is still out of the range of your typical multimeter.

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Unless you have an ESR meter, you can't perform a meaningful test on these caps. Before sending you off to replace 23 electrolytic caps (which may not fix the problem), how about performing a few meaningful tests to verify there is a problem?

1. With the monitor disconnected from the computer, plug the monitor in to power. Does the power LED come on in active mode (green or blue)? If it comes on in standby mode (amber), or doesn't come on at all, does it respond when you push the power button? Does the monitor display anything on the screen at any time?

2. If nothing you do will bring the monitor to active mode, it's time to check a few things on the signal card. U10 and U11 are voltage regulators. Use the bare metal around the mounting point in the upper left corner as the ground point. Measure and report the voltages on the three pins of U10 (pin 1 is on the right in the picture) and U11 (pin 1 is toward the top of the picture). What are the part numbers of U10 and U11?

Edit: I see you have gone ahead and ordered new caps. A few points:
1. The replacement caps should be name brand, low ESR caps.
2. You might as well replace all electrolytic caps (all 23 of them) on both the power supply / inverter and the signal card.
3. The reason you aren't seeing any indication on the small blue caps is their capacitance is too low to register. It's a little like concluding a bathroom scale is defective because it doesn't change when a fly lands on it.

PlainBill

1) It's definitely not the cable's etc. Once the power supply is plugged in the orange LED comes on, it should be green first then change to orange. Nothing I do changes anything, pressing buttons etc. etc.

2) Once I get home from work I will do this (what picture are you referring to by the way?) do I plug the screen in while measuring? Or can I do this while it's powered off? (I think you mean powered on? As powered off it will read zero?)

1. I just bought exactly the same ones, I could only find one seller on ebay anyway.

2. All of them? I thought this was going to be a little easy! Lol, looks like I'll be needed to buy a few more caps (electorlytic are the cylindrical ones right?).

3. Why do most of them register (the resistance fluctuates - but does change), but some of them the multimeter does not change (they are all exactly exactly the same capacitance - the board has loads of small blue caps).

When the capacitor has a significant capacitance value, the time in which it charges from the voltage presented by your multimeter in resistance measuring mode, is slow enough for you to see on the meter. The cap will show low resistance at first, then climb up till it goes over range.

The amount of current that gets lost due to parallel resistance, among other factors is called leakage current. It is very small compared to the ripple current the capacitor normally faces, and rarely exceeds a few microamps. (1 uA = 0.000001 A) Now, if the leakage current of the capacitor is 1 micro amp at 16 volts, and all of it is due to parallel resistance (which it is not), then the resistance of the capacitor would be 16 megohms. This is still out of the range of your typical multimeter.

Thanks guys for your help, I will try and order some philips caps to replace the electorlytic ones - I read the Elite brand ones are known to be bad so I'll start with those first.

At least I'm prepared, I've got a decent multimeter, soldering iron and a solder sucker

[PlainBill]

Re: AG Neovo F-419 Stuck in powersave mode.

A: I was referring to the pictures you linked to. You send me off to chase down pictures; I return the favor.

B: Ebay sellers are notorious for selling counterfeit caps. Others have indicated there is only one seller who provides genuine name brand caps.

C: Of COURSE the tests are to be done with power on.

PlainBill

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Ok, i've checked out the caps on the board and they seem to checkout OK, I have a ISO-TECH IDM69 multimeter, and has a 3-3000uf cap testing range.

Can I assume that my multimeter is correct? And the caps don't need to be replaced?

(I'll measure the voltages once I can grab a kettle lead). I can't find any bulging/broken caps which is frustrating.

[retiredcaps]

Re: AG Neovo F-419 Stuck in powersave mode.

I have a ISO-TECH IDM69 multimeter, and has a 3-3000uf cap testing range.

As others have mentioned, testing for uF and testing for ESR are two totally different things. I don't know of any digital multimeter (even the high end ultra expensive Flukes) that tests ESR (equivalent series resistance). You need a specialized ESR meter to test for ESR.

A cap can be uF correct, but have high ESR. For example, a 1000uF 10V cap might measure 999uF on your Iso-tech multimeter, but the cap's ESR could 21 ohms (which is high).

[PlainBill]

Re: AG Neovo F-419 Stuck in powersave mode.

To add to what retiredcaps said, there are three possible causes for this problem.

1. One or more bad capacitors are causing problems with the processors on the signal card.

2. The firmware for the signal card processors has become corrupted because of excessive ripple on the signal card OR one of the processors may have failed NOT due to any possible problems with the power supply caps.

3. One of the voltage regulators on the signal card has failed, causing the problem you see.

Cause 1 can be repaired by replacing the caps. Without an ESR meter, the only solution is to replace ALL of them.

Cause 2 cannot be repaired except by replacing the signal card.

Cause 3 can be detected by measuring the output of the regulators; replacing the defective regulator should fix the problem.

PlainBill

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Ok, i've got the readings for you today, I put the black lead on the screw that grounds it (top left hand corner):

U10 - reading pins from left to right:
4.82 V
3.30 V
00.2 mV

U11 Reading pins from top to bottom:
00.3 mV
1.808 V
3.46 V

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

Readings look fine. Your problem isn't the regulators.

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

which caps should I buy? I'm looking at some rubycon caps from rs, but have a lifetime of only 2k hours? Which only 1 year. Am I missing something?

[retiredcaps]

Re: AG Neovo F-419 Stuck in powersave mode.

but have a lifetime of only 2k hours? Which only 1 year. Am I missing something?

See PCBONEZ explain lifetime at

https://www.badcaps.net/forum/showpo...30&postcount=7

[rash.m2k]

Re: AG Neovo F-419 Stuck in powersave mode.

Cool, I've read it, just to double check the following caps are on the inverter board:

470uF 25v x5
1000uF 16v x1
10uF 50v x2
470uF 16v x1
10uF 100v x1

And the following on the signal board:

1000uF 10v x1
220uF 16v x7
100uF 16v x3
10uF 16v x 2

And I plan to buy the following caps from RS to replace them.

For inverter board:
10uF 250V 10x16
470uF 35V 10x16
1000uF 16V 10x16

(Will the 25v 470uF be fine for the 16v one? And will the 250V 10uF be fine for the both 50V and 100V)

Signal board:
1000uF 10V 10x12.5
220uF 25V 8x9
16V,100uF
16V,10uF

Will the 25V 220uF be fine for the be OK for the 16v.

A quick nod from anyone is welcome so I can go ahead and order.

Thanks.

[Th3_uN1Qu3]

Re: AG Neovo F-419 Stuck in powersave mode.

If RS means Radio Shack forget it. They don't carry low-ESR caps. They might work... for a month or so.

Buy either from here (badcaps.net store), Digikey or Mouser.