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**mockingbird** · 11-09-2010, 10:12 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Off the top of my head, get someone with the same board revision as you to check the original caps and their series, and make sure you matched these series correctly (i.e. How do you know that you replaced them correctly if the guy before you may have tampered with it and replaced it with an incorrect cap which you are basing your replacements off of). I'm not an expert, but if the monitor is working but shutting off after a while, it most certainly seems like something is wrong with the capacitors.

**newbie1** · 11-09-2010, 10:25 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by mockingbird View Post

Off the top of my head, get someone with the same board revision as you to check the original caps and their series, and make sure you matched these series correctly (i.e. How do you know that you replaced them correctly if the guy before you may have tampered with it and replaced it with an incorrect cap which you are basing your replacements off of). I'm not an expert, but if the monitor is working but shutting off after a while, it most certainly seems like something is wrong with the capacitors.

thanks mockingbird for the suggestion,.. i do not have the physical resources to based the correct caps except the thread by CapBlown.. After going through all the pictures, i am pretty convinced that i did replaced the caps with the identical values as his thread.. Unless, he can advise me otherwise..

**PlainBill** · 11-09-2010, 01:17 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

IC102 is shutting down. It may be defective, overheating, or something else is drawing excess current and preventing it from restarting. What is it's part number?

PlainBill

**newbie1** · 11-09-2010, 04:49 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by PlainBill View Post

IC102 is shutting down. It may be defective, overheating, or something else is drawing excess current and preventing it from restarting. What is it's part number?

PlainBill

Good afternoon PlainBill,

IC102 marking -
J615
TOP247YN
38578A

datatsheet here

I did some voltage measurement (Kindly see 3.4 on Post #1) which BUSTED my DMM while measuring the Drain pin.. Also I did measure resistance on the pins, before my DMM goes south, Pins 1 & 5 are shorted to each other & Pins 2 & 4 are shorted to each other as well..

How do I tell whether it is defective or overheating or something else is drawing excess current? Any measurement ot test to confirm this?. many thanks sir..

**PlainBill** · 11-09-2010, 07:43 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by newbie1 View Post

Good afternoon PlainBill,

IC102 marking -
J615
TOP247YN
38578A

datatsheet here

I did some voltage measurement (Kindly see 3.4 on Post #1) which BUSTED my DMM while measuring the Drain pin.. Also I did measure resistance on the pins, before my DMM goes south, Pins 1 & 5 are shorted to each other & Pins 2 & 4 are shorted to each other as well..

How do I tell whether it is defective or overheating or something else is drawing excess current? Any measurement ot test to confirm this?. many thanks sir..

Thanks for the datasheet. I would have wasted a lot of time by looking at for wrong number.

Looking through the datasheet, I can understand if pins 4 and 5 were shorted together; that is a common circuit configuration. I cannot conceive of any other pins connected which would allow it to work. Yes, contacting the D pin (pin 7) could cause problems with a DMM. That pin probably reaches voltages in excess of 600 VDC!!

My best suggestion is to unsolder the IC and use your new DMM to check for shorts between the pins.

PlainBill

**newbie1** · 11-09-2010, 11:35 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Roger that...

I will proceed with re-soldering my new fuse, & desoldering IC102 to measure for shorts. Before that, just a thought, but I don't know whether I am making sense here & do please correct me if I am wrong.

Having read page 6 of the datasheet, it seems to me that since Pins 1 (Control) & 5 (Frequency) are shorted to each other and Pins 2 (Line-sense) & 4 (Source) are shorted to each other as well, IC102 is behaving :
1) Input pin for selecting switching frequency is 66 kHz since it is connected to CONTROL pin.
2) Input pin for OV, UV, line feed forward with DCMAX reduction, remote ON/OFF and synchronization is DISABLED on this pin because it is connected to SOURCE pin.

I do not know whether these has any impact to the functionality of IC102. Some differences that I like to highlight by looking at my board again & comparing with the Rev2 & Rev3 boards from Capblown thread (attached),

> Rev2 – R127 & R129 are smd resistors labeled 335;
R131 is smd resistor labeled 1004;
Pins 2 & 4 of IC102 looks like they are not connected to each other in my eyes

> Rev3 - R127 & R129 are smd resistors labeled 515;
R131 is not mounted;
Pins 2 & 4 of IC102 looks like they are connected to each other in my eyes using R171

> My board - R127 & R129 are smd resistors labeled 335 (appear to be re-soldered);
R131 is not mounted;
Pins 2 & 4 of IC102 looks like they are connected to each other in my eyes using just excessive solder

FYI, I measured that R129 is shorted (connected) to Pin 3 (External current limit) of IC102.
So do you think, before I desolder IC102, that I should try this
- disconnect Pins 2 & 4 of my board & insert an axial resistor (1000M ohms) on R131, just like Rev2 & see whether it will work?
- Any danger of me adding to the list of casualties by doing the above?

Attached Files

**PlainBill** · 11-10-2010, 06:53 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

You did catch some nuances of the data sheet which completely escaped my attention. My mistake.

It's your board, you can do whatever you want. My suggestion was based on several points.

1. The most likely reason for the problem is the SMPS controller was overheating and shutting down to protect itself.

2. This is a high stress application, historically the SMPS controller / power FET combination is less reliable than using two individual parts.

3. The fact that the SMPS controller went into a coma after destroying your DMM could indicate it experienced permanent damage.

It has been my observation that the people here fall into three classes.
1. The 'I'll throw parts at it until I fix it or give up' group. Thankfully we don't have many of them.
2. The 'I'll ask for help and replace the suggested parts' group. These tend to have a high success rate while buying a minimal number of unnecessary parts.
3. The 'I want to understand how this thing works in exquisite detail, then rebuild it for maximum reliability' group. These are relatively rare; obviously you are one of them. That is not a BAD thing.

PlainBill

**newbie1** · 11-10-2010, 08:30 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by PlainBill View Post

You did catch some nuances of the data sheet which completely escaped my attention. My mistake.

It's your board, you can do whatever you want. My suggestion was based on several points.

1. The most likely reason for the problem is the SMPS controller was overheating and shutting down to protect itself.

2. This is a high stress application, historically the SMPS controller / power FET combination is less reliable than using two individual parts.

3. The fact that the SMPS controller went into a coma after destroying your DMM could indicate it experienced permanent damage.

It has been my observation that the people here fall into three classes.
1. The 'I'll throw parts at it until I fix it or give up' group. Thankfully we don't have many of them.
2. The 'I'll ask for help and replace the suggested parts' group. These tend to have a high success rate while buying a minimal number of unnecessary parts.
3. The 'I want to understand how this thing works in exquisite detail, then rebuild it for maximum reliability' group. These are relatively rare; obviously you are one of them. That is not a BAD thing.

PlainBill

PlainBill, really sorry if i seemed to be doubting your judgment/suggestion in my earlier post, because honestly i wasn't.. And also scrapped my stupid idea.. i do not want to risk having my other half to call 911..

Gratefully appreciate on the explanations & accepted the 3 points of your suggestion,.. I just managed to desoldered the IC102 a while ago.. For those of you with similar board, to take it off, you must unscrew it from the heatsink first, then unscrew the heatsink (2 screws at the bottom) & desolder the 4-pin bridge rectifier (BD101).. removing the heatsink & BD101 leaving the IC102 still sticking on the board.. Then desolder it.. Measured for short in-between the individual pins but can found none shorted. Currently, I have not fixed it back, in case there are other measurement/s to take.

I also measured on the solderpads that IC102 was attached on the board and found that Pins 1 (Control) & 5 (Frequency) solderpads are internally shorted but Pins 2 (Line-sense) & 4 (Source) are not.

Hope you can continue guiding me what to do next..
thanks again sir..

**jetadm123** · 11-10-2010, 09:54 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Late to to the party.... I may have missed something, but after the incident with your DMM, does the W20 still power up and shutdown after an hour? If yes, maybe you can accelerate the shutdown process by using a blow dryer set on high heat and try heating up the TOP247 to see if you can cause it to shutdown more quickly. If this works, then the TOP247 (or a surrounding component) could be defective. Worth a try.

**shovenose** · 11-10-2010, 10:33 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Ifyou have the back off and point a fan at it, does it stay on longer? If so, somethings overheating.

**newbie1** · 11-11-2010, 10:26 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Hope the party & Holidays are going great..

Managed to reassembled the IC102 back to the board. Power up fine. But when i switch it off & on again it did not respond. No Power LED on. So am i right to assume that this is unlikely to be heat related which is per my initial assesment of the problem? The heatsink of the IC is not even warm btw. Then I flip the board over to take some voltage readings around IC102 but i do not know whether they are relevant

*Pin C to Gnd (cold start) = 5.28V.. BUT it will drop to 0.72V (stable) if the power switch on the panel is not pressed during the 5.28V period (not turn-on). If I press it during C=5.28V, the voltage remains & monitor works fine.
*Pin C to Gnd (off) = 0.72V
*Pin C to Gnd (unplugged) = 0.72V but changed to 2.3V & decreasing after ~15 sec
* Pin X to Gnd = 0.26V
* Pin X1 to Gnd = 0.26V
* Pin X2 to Gnd = 60V
* Pin X3 to Gnd = >600V!!.

.. Luckily my new DMM has a max of 1000V..

Can anybody confirm whether IC102 is faulty & i need to replace it?.. or is there something else that i might miss out?..

Attached Files

**PlainBill** · 11-11-2010, 01:45 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by newbie1 View Post

Hope the party & Holidays are going great..

Managed to reassembled the IC102 back to the board. Power up fine. But when i switch it off & on again it did not respond. No Power LED on. So am i right to assume that this is unlikely to be heat related which is per my initial assesment of the problem? The heatsink of the IC is not even warm btw. Then I flip the board over to take some voltage readings around IC102 but i do not know whether they are relevant

*Pin C to Gnd (cold start) = 5.28V.. BUT it will drop to 0.72V (stable) if the power switch on the panel is not pressed during the 5.28V period (not turn-on). If I press it during C=5.28V, the voltage remains & monitor works fine.
*Pin C to Gnd (off) = 0.72V
*Pin C to Gnd (unplugged) = 0.72V but changed to 2.3V & decreasing after ~15 sec
* Pin X to Gnd = 0.26V
* Pin X1 to Gnd = 0.26V
* Pin X2 to Gnd = 60V
* Pin X3 to Gnd = >600V!!.

.. Luckily my new DMM has a max of 1000V..

Can anybody confirm whether IC102 is faulty & i need to replace it?.. or is there something else that i might miss out?..

I'm questioning my earlier belief that IC102 was defective.

The thing that catches my eye is the behavior of the C input. Why is that dropping to .72 volts? Oh, for a schematic!!!

PlainBill

**jetadm123** · 11-11-2010, 08:56 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by newbie1 View Post

Hope the party & Holidays are going great..

No Power LED on. So am i right to assume that this is unlikely to be heat related which is per my initial assesment of the problem? The heatsink of the IC is not even warm btw. Then I flip the board over to take some voltage readings around IC102 but i do not know whether they are relevant.

If you were still having the shutdown problems you decribed in post#1, I would say you did have a thermal problem and recommend what capblown did on the thread you listed:

https://www.badcaps.net/forum/showth...=hp+w20&page=2

Looking at post #35, he provides a photo of all the points he resoldered to solve his problem.

You're saying that after reinstalling the top247, you get nothing, except when "C" is around 5.28V and you press the on/off button and the monitor powers on and shuts down approx. after an hour. Correct? I would go ahead and reflow the solder at the points capblown outlined to see if that helps with the shutdown problem.

If resoldering has no effect, then try lowering the brightness to see if the lower current draw prolongs the "on" time of the monitor.

**newbie1** · 11-12-2010, 05:03 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by PlainBill View Post

I'm questioning my earlier belief that IC102 was defective.

The thing that catches my eye is the behavior of the C input. Why is that dropping to .72 volts? Oh, for a schematic!!!

PlainBill

PlainBill, I am also doubting myself about my description in post #1. I think the way I test it the first time (Switch on & let it run until it shutdown during standby/sleep mode) is WRONG. It makes other people including myself, think that I am having heat related problem with this monitor. BUT, now after monitoring the control pin of IC102 I believe I should have checked whether it will respond to pressing the on/off switch (able to restart), which is not the case now, unless if you correctly time it when Pin 1 (Control) = 5.28V. FYI, I am also not comfortable with the condition of R127 & R129 (labeled 335 & appears to be re-soldered) which is linking to Pin 3 (External Current Limit). Any thoughts?
BTW, if you don’t mind me asking, Pin 1 (Control) needs at least 4.5V for it to power up right? And what is Auto-restart hysteresis voltage (min 0.8V)?

I have googled for the schematics but is unsuccessful so far. Sigh!. Anybody knows
of sites that I can check with. Or maybe I should follow Capblown example & take a zoom-up picture of that area & trace-out the link of the pins connecting to which components that might makes Pin 1 to drop voltage. However I am not sure whether I can be THAT artistic with all the colors. Lol!. Sometimes, my wife gave me ‘that look’ that signals to me, why on earth, at this age, am I still wasting my sleeping hours doing my colleges tutorials & practical experiments at home. Insane?.. Lol..

Originally posted by jetadm123 View Post

If you were still having the shutdown problems you decribed in post#1, I would say you did have a thermal problem and recommend what capblown did on the thread you listed:

https://www.badcaps.net/forum/showth...=hp+w20&page=2

Looking at post #35, he provides a photo of all the points he resoldered to solve his problem.

You're saying that after reinstalling the top247, you get nothing, except when "C" is around 5.28V and you press the on/off button and the monitor powers on and shuts down approx. after an hour. Correct? I would go ahead and reflow the solder at the points capblown outlined to see if that helps with the shutdown problem.

If resoldering has no effect, then try lowering the brightness to see if the lower current draw prolongs the "on" time of the monitor.

jetadm123, noted on re-soldering ALL 60 solder joints. *GULP!* As I mentioned above, maybe I am not testing the monitor correctly the first time. Just to clarify the current status is –

1) From cold start, I can turn –on the monitor IF I pressed the power button while Pin 1 (Control) = 5.28V but I have not tested it long enough to see whether it will AUTO shutdown, though. Note that Pin 1 (Control) will have a drop voltage to 0.7V after a few seconds. If I miss that window & pressed the switch when Pin 1 (Control) = 0.7V, it will not start/re-start.

2) Pin 1 (Control) = 0.7V is stable with power plugged. Once I unplugged AND AFTER 15 sec Pin 1 (Control) = 2.3V and keep on decreasing.

3) If I plugged it again now, Pin 1 (Control) = 5.28V for a few seconds then drop to 0.7V again.

Hope I am clear enough, man. Ok, I will try lowering the brightness & contrast & see whether Pin 1 will not drop voltage.

p/s : i don't know whether i can kill 2 bird with 1 stone.. but my items to repair the HP f1905 in my other thread arrived just now. so will be soldering & fixing that guy first.. sorry if i do not update this anytime soon..

**PlainBill** · 11-12-2010, 07:22 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Light bulb just went on - darn CCFL. The key must be pin 1. Where is the voltage source?

When you get a chance, I've marked off the area of interest on the bottom of the PC board. At a minimum I would like the pins of IC102 identified.

You had asked about hysteresis. The start-up circuit of an SMPS controller is designed with hysteresis. As the input voltage rises, the controller starts when the voltage reaches 16 volts. It will continue to operate until the input voltage drops below 11 volts. When the input voltage rises again it will start when it reaches 16 volts.

PlainBill

Attached Files

**newbie1** · 11-12-2010, 07:46 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Originally posted by PlainBill View Post

Light bulb just went on - darn CCFL. The key must be pin 1. Where is the voltage source?

When you get a chance, I've marked off the area of interest on the bottom of the PC board. At a minimum I would like the pins of IC102 identified.

You had asked about hysteresis. The start-up circuit of an SMPS controller is designed with hysteresis. As the input voltage rises, the controller starts when the voltage reaches 16 volts. It will continue to operate until the input voltage drops below 11 volts. When the input voltage rises again it will start when it reaches 16 volts.

PlainBill

HAHA! I think we must change to LED lights now.

I will try to findout later where the voltage source of Pin 1 is coming from.. I have the time anyway since my HP1905 is till not solved..In the meantime, I have marked the pins of IC102 in the pix attached. Also i have inserted some notes on the differences between the image & my board..
Legend
C = pin 1 (also internally connected to Pin 5)
L = pin 2
X = pin 3
S = pin 4
F = pin 5
D = pin 7

Many thanks on the explanation on hysteresis, boss.. Your explanation is much much clearer & easier to understand than the one that found through googgled just now... Appreciate it..

.. Can i nominate you for a Noble prize award or something like that?..

Attached Files

**jetadm123** · 11-12-2010, 08:28 AM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Quickly looking over the IC102 spec sheet (page 6) I notice that pin 1 (C) should have a startup cap (47uf?) connected to it. Can you verify this? Apparently, you need 5.8V across this cap for startup to begin. Try replacing this cap. Hopefully, you have a spare cap lying around for testing, say, maybe from a junked power supply?

**newbie1** · 11-12-2010, 06:21 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Very correct. I have trace out in the attached photo the pins & to where they are linking to. Yes, Pin 1 is connected to cap 47uf 50V which i already replaced with Nichicon PS. Do you think I should replaced it again?. All i have spare now for this, is the same capacitor type no Panasonic. Unless you think I can replaced it with a 22uF 50V Panasonic FM i have lying around.

The photo is only taken on some part of the circuits. My camera is not very good i guess to take a zoom out image with readable markings on the board. If a bigger area is needed to trace out the voltage source, I will re-take again. I also attach the top side.

Attached Files

**jetadm123** · 11-12-2010, 08:22 PM

Re: HP w20. Total Shutdown. Cannot turn-on immediately.

Oops! Forgot about the fact that you already changed the 47uf cap. Back to the drawing board.

Also, what is the model number of the power board? Li Shin XXXXX

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HP w20. Total Shutdown. Cannot turn-on immediately.

HP w20. Total Shutdown. Cannot turn-on immediately.

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