GNR TS902W no power , help please

[lcdcaps1]

Re: GNR TS902W no power , help please

Ok
I wasn't going to use it. Just asking if it can be
Now i no.
I'll get a light bulb

Please can you let me know which points i need to solder the bulb to on my board

Thanks

DO NOT USE THAT in place of the incandescent bulb!
It is rated for 200W @ 12V only. That means that at 240V, it will try to dissipate over 3000 Watts if something on the PSU short-circuits.

Again, the whole idea of the series incandescent bulb (or heating element) is to LIMIT the amount of power/current, in case something short-circuits on the PSU board. With that heating element you posted above, this will NOT work and you will end up with just as many blown parts as if you just plugged the power supply straight into the wall.

There's a reason why I said in my above posts that your incandescent light bulb (or heating element) needs to be rated for 230/240 Volts. Please read them carefully and don't skip over details, as this is exactly the kind of thing that can make things burn out and possibly set something on fire.

[momaka]

Re: GNR TS902W no power , help please

DO NOT USE THAT in place of the incandescent bulb!
It is rated for 200W @ 12V only. That means that at 240V, it will try to dissipate over 3000 Watts if something on the PSU short-circuits.

Again, the whole idea of the series incandescent bulb (or heating element) is to LIMIT the amount of power/current, in case something short-circuits on the PSU board. With that heating element you posted above, this will NOT work and you will end up with just as many blown parts as if you just plugged the power supply straight into the wall.

There's a reason why I said in my above posts that your incandescent light bulb (or heating element) needs to be rated for 230/240 Volts. Please read them carefully and don't skip over details, as this is exactly the kind of thing that can make things burn out and possibly set something on fire.

[lcdcaps1]

Re: GNR TS902W no power , help please

Hi
This is the one i have
https://www.ebay.com/itm/AC-DC12V-20...-/302453704967

it runs on 12v

Well, what is it?
To me, it looks like a heating element (heater). If that's so, what voltage and power (Watts) is it rated for?

Probably best to find something in the 100-300 Watt range. But if not possible, up to 500W should be okay.

[momaka]

Re: GNR TS902W no power , help please

So i was looking on what i can use for an alternative to a. Bulb
I found this

https://ae01.alicdn.com/kf/HTB1Hi0GK...pg_640x640.jpg

Well, what is it?
To me, it looks like a heating element (heater). If that's so, what voltage and power (Watts) is it rated for?

Probably best to find something in the 100-300 Watt range. But if not possible, up to 500W should be okay.

[lcdcaps1]

Re: GNR TS902W no power , help please

Hi
Thanks for the reply
So ive ordered replacements to be safe
Should arrive soon

So i was looking on what i can use for an alternative to a. Bulb
I found this

https://ae01.alicdn.com/kf/HTB1Hi0GK...pg_640x640.jpg

I have one of these or similar
Please let me know

Thanks

I know incandescent bulbs are obsolete now. But what about halogen type of similar power (40-100 Watts) rated for 230/240V?? Do you have any bulbs like that?

Other alternatives are a device with a 200-500 Watt heating element of some sort (like a toaster, mini oven, hair dryer on low setting, and etc.)


Yes, removing fuse F200 should still allow the monitor to turn on, but without the backlights. Essentially, removing fuse F200 cuts power off from the inverter section - i.e. power to those 40T03GP MOSFETs. Thus, if they are bad, now they won't make the power supply shut down.

So rather than replacing them blindly, we just disable the whole inverter and see if the power supply can turn on. If yes, then we know the problem is somewhere in the inverter section. If not, then there's still an issue elsewhere.

[momaka]

Re: GNR TS902W no power , help please

I dont have any bulbs
Is there any other way to do this

I know incandescent bulbs are obsolete now. But what about halogen type of similar power (40-100 Watts) rated for 230/240V?? Do you have any bulbs like that?

Other alternatives are a device with a 200-500 Watt heating element of some sort (like a toaster, mini oven, hair dryer on low setting, and etc.)

If i remove fuse and power on will it work

Yes, removing fuse F200 should still allow the monitor to turn on, but without the backlights. Essentially, removing fuse F200 cuts power off from the inverter section - i.e. power to those 40T03GP MOSFETs. Thus, if they are bad, now they won't make the power supply shut down.

So rather than replacing them blindly, we just disable the whole inverter and see if the power supply can turn on. If yes, then we know the problem is somewhere in the inverter section. If not, then there's still an issue elsewhere.

[lcdcaps1]

Re: GNR TS902W no power , help please

I dont have any bulbs
Is there any other way to do this
If i remove fuse and power on will it work

I was reading about similar boards that had the troublesome 40T03GP

Others replaced these and restored full power to the monitor
I dont have these or alternatives mentioned to hand and if i order they will take along time to arrive.

The substitutes mentioned vary in values

I have found some that are higher spec..
5r250p
Will these be ok to use or to test just to see if the monitor gets it voltages please
Please let me know

Thanks in advance
[/B][/B]

That's one way to test the output voltage rails for short circuit. And it looks like nothing is shorted / bad.

Next, try the following...
Use the series incandescent trick I mentioned in post #66 above, i.e. this:
https://www.badcaps.net/forum/showpo...4&postcount=70
And plug in the monitor PSU. Observe what the incandescent light bulb does and note it down (to post it here).

Next, remove one side of green fuse F200 or just remove it altogether (it's right next to the main Delta transformer). Now try powering on the PSU again. What does the incandescent light bulb do? Also, do you get any output voltages on the white connector that goes to the LCD logic board? If yes, post what they are.

After this, I have only two more tests/experiments we can do if we don't find anything conclusive again.

[momaka]

Re: GNR TS902W no power , help please

another test i done is
i checked resistance to ground from the white ribbon cable

I used screw hole as ground

That's one way to test the output voltage rails for short circuit. And it looks like nothing is shorted / bad.

Next, try the following...
Use the series incandescent trick I mentioned in post #66 above, i.e. this:
https://www.badcaps.net/forum/showpo...4&postcount=70
And plug in the monitor PSU. Observe what the incandescent light bulb does and note it down (to post it here).

Next, remove one side of green fuse F200 or just remove it altogether (it's right next to the main Delta transformer). Now try powering on the PSU again. What does the incandescent light bulb do? Also, do you get any output voltages on the white connector that goes to the LCD logic board? If yes, post what they are.

After this, I have only two more tests/experiments we can do if we don't find anything conclusive again.

[lcdcaps1]

Re: GNR TS902W no power , help please

another test i done is
i checked resistance to ground from the white ribbon cable

I used screw hole as ground

looking from back of the board, with white line to the left (mark line to show hot and cold side)
This is pin 1 for this test

Pin 1
000.6 ohm

pin 2
000.6 ohm

pin 3
OL

pin 4
Kilo ohms reading

pin 5
Kilo ohms reading

pin 6
Kilo ohms reading

pin 7
Kilo ohms reading

pin 8
Kilo ohms reading

pin 9
Kilo ohms reading

pin 10
Kilo ohms reading

pin 11
OL

Welp, that's a start.

Certainly makes one wonder if the first replacement PWM chip you tried was defective or not (or perhaps not soldered all the way / all pins??)

1.1V is low for the PWM controller to start. But the fact that we get a voltage there now means at least it might be trying to.

So try this:
With the PSU unplugged, put multimeter probes on board to test for voltage on pin 7. Now plug-in the PSU while the multimeter probes are still connected and watch the voltage on the multimeter screen. Does the voltage pulse up to a higher value once before settling to 1.1V? On that note, if your multimeter has a Min/Max feature, use it to see if there is a higher voltage pulse on there.

What we're trying to see here is if the PWM is actually trying to start, encounters a problem, then shuts down and does not resume or latches in the OFF/fault state (I suppose perhaps Q103 could be responsible for that??)

That being said, with the PSU disconnected from wall, measure resistance between the output rails of the PSU and ground. Post what results you get here (or if you need help finding these). The output rails should be the cathode of each output rectifier on the secondary-side (you said you already replaced one of them due to showing bad.)

[lcdcaps1]

Re: GNR TS902W no power , help please

I done as you suggested by keeping probes on pin 7 and powering on
my multimeter did not show any voltage pulse

Welp, that's a start.

Certainly makes one wonder if the first replacement PWM chip you tried was defective or not (or perhaps not soldered all the way / all pins??)

1.1V is low for the PWM controller to start. But the fact that we get a voltage there now means at least it might be trying to.

So try this:
With the PSU unplugged, put multimeter probes on board to test for voltage on pin 7. Now plug-in the PSU while the multimeter probes are still connected and watch the voltage on the multimeter screen. Does the voltage pulse up to a higher value once before settling to 1.1V? On that note, if your multimeter has a Min/Max feature, use it to see if there is a higher voltage pulse on there.

What we're trying to see here is if the PWM is actually trying to start, encounters a problem, then shuts down and does not resume or latches in the OFF/fault state (I suppose perhaps Q103 could be responsible for that??)

That being said, with the PSU disconnected from wall, measure resistance between the output rails of the PSU and ground. Post what results you get here (or if you need help finding these). The output rails should be the cathode of each output rectifier on the secondary-side (you said you already replaced one of them due to showing bad.)

[lcdcaps1]

Re: GNR TS902W no power , help please

the legs below i high lighted are not connected to the big cap and diode
but the legs high lighted before are but there are two points that connect to the diode and capacitor

That is correct.
Drain is connected to the main primary-side winding of the transformer, which is also connected to the input/bulk cap's positive lead (324V).
Meanwhile, Source is connected to primary-side ground (input/bulk cap's negative lead) through a low-resistance resistor for detecting over-current condition on the primary - that would be R126-1/2/3.

So all these readings are normal.


I'll get to that in more detail in my next post.


Very unlikely. I've actually never seen a power transformer from an SMPS go bad, save for a small 5VSB transformer in an ATX PSU once.


That is correct / the way it should be.

Now with the power to the PSU disconnected, what resistance do you get between the two transformer legs below the ones you highlighted in yellow in this picture?
https://www.badcaps.net/forum/attach...3&d=1530399728
(To find these legs, one of them connects to anode-side of diode D103. The other leg connects to primary-side input/bulk cap's negative lead).

Ideally, you should get no more than 1-2 Ohms (i.e. short-circuit). This is normal, because SMPS transformers have very few turns inside, so they appear like a piece of wire.


No thermal fuse inside these transformers. They have very thick windings, as mentioned above, so they cannot burn out. You'd have to connect one to the wall plug in your house with no fuse, and even then it's likely you'll trip breaker in your house before the transformer gets damaged.

So that's not the issue. But we will keep looking. I have a few ideas. Just need to analyze the boards (pictures you provided) a bit more so I can suggest more testing procedures of things we might have missed.

[lcdcaps1]

Re: GNR TS902W no power , help please

Welp, that's a start.

Certainly makes one wonder if the first replacement PWM chip you tried was defective or not (or perhaps not soldered all the way / all pins??)

1.1V is low for the PWM controller to start. But the fact that we get a voltage there now means at least it might be trying to.

So try this:
With the PSU unplugged, put multimeter probes on board to test for voltage on pin 7. Now plug-in the PSU while the multimeter probes are still connected and watch the voltage on the multimeter screen. Does the voltage pulse up to a higher value once before settling to 1.1V? On that note, if your multimeter has a Min/Max feature, use it to see if there is a higher voltage pulse on there.

What we're trying to see here is if the PWM is actually trying to start, encounters a problem, then shuts down and does not resume or latches in the OFF/fault state (I suppose perhaps Q103 could be responsible for that??)

That being said, with the PSU disconnected from wall, measure resistance between the output rails of the PSU and ground. Post what results you get here (or if you need help finding these). The output rails should be the cathode of each output rectifier on the secondary-side (you said you already replaced one of them due to showing bad.)

i replaced the diode schottky rectifier, 3 pin in the heat sink
please tell me how to find the rails, ive been using the ribbon cable
thanks

[momaka]

Re: GNR TS902W no power , help please

ok so a bit of an update
i replaced the pwm chip again

now i get
on pin 3
22.70 v

on pin 7
1.1v

also startup cap has some voltage
1v

Welp, that's a start.

Certainly makes one wonder if the first replacement PWM chip you tried was defective or not (or perhaps not soldered all the way / all pins??)

1.1V is low for the PWM controller to start. But the fact that we get a voltage there now means at least it might be trying to.

So try this:
With the PSU unplugged, put multimeter probes on board to test for voltage on pin 7. Now plug-in the PSU while the multimeter probes are still connected and watch the voltage on the multimeter screen. Does the voltage pulse up to a higher value once before settling to 1.1V? On that note, if your multimeter has a Min/Max feature, use it to see if there is a higher voltage pulse on there.

What we're trying to see here is if the PWM is actually trying to start, encounters a problem, then shuts down and does not resume or latches in the OFF/fault state (I suppose perhaps Q103 could be responsible for that??)

That being said, with the PSU disconnected from wall, measure resistance between the output rails of the PSU and ground. Post what results you get here (or if you need help finding these). The output rails should be the cathode of each output rectifier on the secondary-side (you said you already replaced one of them due to showing bad.)

[momaka]

Re: GNR TS902W no power , help please

The only pin i have voltage is drain

That is correct.
Drain is connected to the main primary-side winding of the transformer, which is also connected to the input/bulk cap's positive lead (324V).
Meanwhile, Source is connected to primary-side ground (input/bulk cap's negative lead) through a low-resistance resistor for detecting over-current condition on the primary - that would be R126-1/2/3.

So all these readings are normal.

How can i make sure the transistors are not shorted on the secondary side

I'll get to that in more detail in my next post.

Could the problem i am facing be a transformer issue

Very unlikely. I've actually never seen a power transformer from an SMPS go bad, save for a small 5VSB transformer in an ATX PSU once.

Attached is pic that has high lighted in yellow the pins i get voltage on. This is one side of the yellow transformer that has delta writing on top. Also high lighted other pins where i get voltage

i get 328 v dc on the pins mentioned above
but nothing on other side

That is correct / the way it should be.

Now with the power to the PSU disconnected, what resistance do you get between the two transformer legs below the ones you highlighted in yellow in this picture?
https://www.badcaps.net/forum/attach...3&d=1530399728
(To find these legs, one of them connects to anode-side of diode D103. The other leg connects to primary-side input/bulk cap's negative lead).

Ideally, you should get no more than 1-2 Ohms (i.e. short-circuit). This is normal, because SMPS transformers have very few turns inside, so they appear like a piece of wire.

Could the thermal fuse inside the transformer be bad.

No thermal fuse inside these transformers. They have very thick windings, as mentioned above, so they cannot burn out. You'd have to connect one to the wall plug in your house with no fuse, and even then it's likely you'll trip breaker in your house before the transformer gets damaged.

So that's not the issue. But we will keep looking. I have a few ideas. Just need to analyze the boards (pictures you provided) a bit more so I can suggest more testing procedures of things we might have missed.

[lcdcaps1]

Re: GNR TS902W no power , help please

ok now im getting

ok so a bit of an update
i replaced the pwm chip again

now i get
on pin 3
22.70 v

on pin 7
3.2v
also this is the same voltage across the start up cap


also startup cap has some voltage
1v

[lcdcaps1]

Re: GNR TS902W no power , help please

ok so a bit of an update
i replaced the pwm chip again

now i get
on pin 3
22.70 v

on pin 7
1.1v

also startup cap has some voltage
1v

[lcdcaps1]

Re: GNR TS902W no power , help please

The esr for the big cap is 0.91
Ive replaced the opto and tl431 to rule out

Attached is pic that has high lighted in yellow the pins i get voltage on. This is one side of the yellow transformer that has delta writing on top. Also high lighted other pins where i get voltage

i get 328 v dc on the pins mentioned above
but nothing on other side

Could the thermal fuse inside the transformer be bad.
Thanks again all

It could be the transformer, what voltages do you get on it (be careful again). ESR for the big cap should be low, lower than 2 ohms, best is below 1 ohm.

[rddube]

Re: GNR TS902W no power , help please

It could be the transformer, what voltages do you get on it (be careful again). ESR for the big cap should be low, lower than 2 ohms, best is below 1 ohm.

[lcdcaps1]

Re: GNR TS902W no power , help please

Could the problem i am facing be a transformer issue

[lcdcaps1]

Re: GNR TS902W no power , help please

what would be a good esr for the big cap

It's a little difficult to tell without the schematics. But I would open the schematics I posted in a previous post (it is not exactly your board but it is very close), and starting at the AC input would trace where I should find voltage.

The labels on the components in the schematics are not exactly the same as on your board but you have the type of component and you could cross-reference it to your actual board. At some point, you're going to hit a spot where you should be having voltage and you don't. The component just before that spot will probably be your culprit.

BTW, you say you have voltage on the big cap? Did you check that caps ESR?