Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting TVs and Video Sources
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 07-03-2010, 05:01 PM   #1
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Daytek DCM-17WT no display

I received a non working Daytek DCM-17WT (circa around 2002/2003). I'm not the original owner so I don't know the history. It is a hybrid LCD TV/computer monitor. The TV side has S-video and composite inputs. The "PC" side has a single VGA input.

SETUP
=====

- known working VGA cable, 15 pin male to male
- known working laptop with VGA output
- known working AC power surger protector
- laptop plugged into Daytek PC side with known working VGA connections
- remote control has fresh known working batteries
- known working DVD player and composite cable plugged into TV side

SYMPTOMS
========

- press power button and Daytek LED will turn green, but there is no picture at all. No flash of the screen, nothing. LED stays green.
- pressing the OSD menu on the TV or remote shows nothing
- pressing the source button on the TV or remote control does not display any picture
- I cannot be sure what the "source" is because there is no OSD display or menu
- if I remove the LVDS cable, the screen goes entirely white and stays that way which infers the inverter board and CCFLs are working okay
- there is a slightly high pitched whine or squeal with the LVDS cable is plugged in. If I disconnect the LVDS cable, that sound is gone.


MEASUREMENTS
============

- external power supply DC12V 4.17A shows steady 12.22V DC with DMM
- inverter board gets 12V DC with DMM
- all fuses show 0.03 ohms with DMM
- LVDS (from left to right) DC voltages are
pin 1-4: 4.88V DC
pin 5-8: 0.00V DC
pin 9: 1.34V DC
pin 10: 1.19V DC
pin 11: 1.34V DC
pin 12: 1.19V DC
pin 13: 1.25V DC
pin 14: 1.28V DC
pin 15: 1.24V DC
pin 16: 1.28V DC
pin 17: 1.36V DC
pin 18: 1.17V DC
- I have no ESR meter, but all the caps look visibly okay except one that *might* have been slightly bloated which I changed. All the original caps are real "K" vent Rubycon YK 85C.
- all front panel buttons test okay (no shorts)

NOTES
=====

- the cap I changed out took a lot of heat, scraping, struggles to get out and I think I damaged or removed the solder pads which explains why it looks so ugly. Solder doesn't stick to PCB very well. The front side logic picture shows the "old" cap in. It looks slightly bloated and I replaced it with a United Chemicon.

- I did test the monitor BEFORE I changed the one cap and I got almost the same voltage measurements on the LVDS.

- I have reseated and cleaned all the connections and verified cable integrity with a DMM using the continuity test.

- I think the problem lies somewhere on the logic board, possibly the pixelworks PW166B-10T chip. I suspect that for two reasons.

First,it looks like it is the chip that processes both PC and TV side inputs. Since neither composite or PC work this might be the choke point.

Second, it looks like this is a BGA implementation and there are numerous reported problems with this type of implementation.

- Datasheet for PW166B is at

http://www.eserviceinfo.com/download.php?fileid=24584

NEXT?
=====

Since the PW166B is a BGA, I cannot easily verify it is working properly. I guess I can infer it is working or not by measuring the outputs and comparing it to the datasheet.

So I'm looking for suggestions on how to proceed or test points.

If the suggestion is to recap the logic board, I can, but I need to order some caps that fit. As you can see, some caps lie on their side to fit underneath the aluminum shield. And these are already Rubycon caps, albeit 2002/2003 circa.
Attached Images
File Type: jpg inverter.jpg (238.4 KB, 252 views)
File Type: jpg logic.jpg (529.2 KB, 308 views)
File Type: jpg logic-back.jpg (354.8 KB, 198 views)
File Type: jpg overall.jpg (356.8 KB, 237 views)

Last edited by retiredcaps; 07-03-2010 at 05:04 PM..
retiredcaps is offline   Reply With Quote
Old 07-03-2010, 06:21 PM   #2
PlainBill
Badcaps Veteran
 
PlainBill's Avatar
 
Join Date: Feb 2009
City & State: Phoenix, AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist
Posts: 7,013
Default Re: Daytek DCM-17WT no display

Quote:
Originally Posted by retiredcaps
I received a non working Daytek DCM-17WT (circa around 2002/2003). I'm not the original owner so I don't know the history. It is a hybrid LCD TV/computer monitor. The TV side has S-video and composite inputs. The "PC" side has a single VGA input.

SETUP
=====

- known working VGA cable, 15 pin male to male
- known working laptop with VGA output
- known working AC power surger protector
- laptop plugged into Daytek PC side with known working VGA connections
- remote control has fresh known working batteries
- known working DVD player and composite cable plugged into TV side

SYMPTOMS
========

- press power button and Daytek LED will turn green, but there is no picture at all. No flash of the screen, nothing. LED stays green.
- pressing the OSD menu on the TV or remote shows nothing
- pressing the source button on the TV or remote control does not display any picture
- I cannot be sure what the "source" is because there is no OSD display or menu
- if I remove the LVDS cable, the screen goes entirely white and stays that way which infers the inverter board and CCFLs are working okay
- there is a slightly high pitched whine or squeal with the LVDS cable is plugged in. If I disconnect the LVDS cable, that sound is gone.


MEASUREMENTS
============

- external power supply DC12V 4.17A shows steady 12.22V DC with DMM
- inverter board gets 12V DC with DMM
- all fuses show 0.03 ohms with DMM
- LVDS (from left to right) DC voltages are
pin 1-4: 4.88V DC
pin 5-8: 0.00V DC
pin 9: 1.34V DC
pin 10: 1.19V DC
pin 11: 1.34V DC
pin 12: 1.19V DC
pin 13: 1.25V DC
pin 14: 1.28V DC
pin 15: 1.24V DC
pin 16: 1.28V DC
pin 17: 1.36V DC
pin 18: 1.17V DC
- I have no ESR meter, but all the caps look visibly okay except one that *might* have been slightly bloated which I changed. All the original caps are real "K" vent Rubycon YK 85C.
- all front panel buttons test okay (no shorts)

NOTES
=====

- the cap I changed out took a lot of heat, scraping, struggles to get out and I think I damaged or removed the solder pads which explains why it looks so ugly. Solder doesn't stick to PCB very well. The front side logic picture shows the "old" cap in. It looks slightly bloated and I replaced it with a United Chemicon.

- I did test the monitor BEFORE I changed the one cap and I got almost the same voltage measurements on the LVDS.

- I have reseated and cleaned all the connections and verified cable integrity with a DMM using the continuity test.

- I think the problem lies somewhere on the logic board, possibly the pixelworks PW166B-10T chip. I suspect that for two reasons.

First,it looks like it is the chip that processes both PC and TV side inputs. Since neither composite or PC work this might be the choke point.

Second, it looks like this is a BGA implementation and there are numerous reported problems with this type of implementation.

- Datasheet for PW166B is at

http://www.eserviceinfo.com/download.php?fileid=24584

NEXT?
=====

Since the PW166B is a BGA, I cannot easily verify it is working properly. I guess I can infer it is working or not by measuring the outputs and comparing it to the datasheet.

So I'm looking for suggestions on how to proceed or test points.

If the suggestion is to recap the logic board, I can, but I need to order some caps that fit. As you can see, some caps lie on their side to fit underneath the aluminum shield. And these are already Rubycon caps, albeit 2002/2003 circa.
An obvious next step would be to check the onboard voltage regulators. I count 7 of them.

PlainBill
Attached Images
File Type: jpg Daytek DCM-17WT logic top-1.JPG (546.0 KB, 242 views)
__________________
For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.
PlainBill is offline   Reply With Quote
Old 07-03-2010, 07:04 PM   #3
PlainBill
Badcaps Veteran
 
PlainBill's Avatar
 
Join Date: Feb 2009
City & State: Phoenix, AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist
Posts: 7,013
Default Re: Daytek DCM-17WT no display

Another trick I use is to hook up an old video game or other signal source with composite out to the composite inputs. Then I step through the inputs until I hear the sound out of the speakers.

PlainBill
PlainBill is offline   Reply With Quote
Old 07-03-2010, 10:45 PM   #4
el3ctroded
Senior Member
 
Join Date: Nov 2008
City & State: NC
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Professional Tech
Posts: 184
Default Re: Daytek DCM-17WT no display

Quote:
Originally Posted by retiredcaps
- the cap I changed out took a lot of heat, scraping, struggles to get out and I think I damaged or removed the solder pads which explains why it looks so ugly. Solder doesn't stick to PCB very well. The front side logic picture shows the "old" cap in. It looks slightly bloated and I replaced it with a United Chemicon.
The reason you had so much trouble is your soldering iron is likely not powerful enough to heat the part and power/gnd copper planes on the PCB, or there was no flux left in the solder, or both. The reason solder didn't want to stick to the board is the same reason: You were likely not getting the solder point hot enough, most likely due to a too-small wattage iron.

I use this 100W iron and on occasion have to turn up the temperature to 900degF (it says max 850, but it goes higher): http://www.xytronic-usa.com/LF-1000_index.htm

Edit: When using the temp so high, you have to be very careful not to damage the PCB or part(s)!

Last edited by el3ctroded; 07-03-2010 at 10:48 PM..
el3ctroded is offline   Reply With Quote
Old 07-04-2010, 11:58 AM   #5
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

Happy 4th of July to all the American readers!

IC 501 - LM25765
================

pin 1 - VIN - 12.23V
pin 2 - OUT - 4.98V
pin 3 - GND
pin 4 - feedback - 4.92V
pin 5 - on/off - 0.01V

IC504 - AME1085
===============

pin 1 - GND
pin 2 - OUT - 3.31V
pin 3 - VIN - 4.92V

IC302 - AMS1117 2.5
===================

pin 1 - GND
pin 2 - OUT - 2.52V
pin 3 - VIN - 4.92V

IC9 - 78M05
===========

pin 1 - VIN - 12.21V
pin 2 - GND
pin 3 - OUT - 5.01V

IC1 - AMS1117 3.3
=================

pin 1 - GND
pin 2 - OUT - 3.31V
pin 3 - VIN - 4.93V

IC702 - AMS1117 3.3
===================

pin 1 - GND
pin 2 - OUT - 3.31V
pin 3 - VIN - 4.93V

IC801 - MC7809C
===============

pin 1 - VIN - 12.21V
pin 2 - GND
pin 3 - OUT - 9.09V

All the voltages look good to me and match the datasheets for input and output.

At first I thought IC302 VOUT was low, but the chip says AMS1117 2.5 which to me indicates 2.5V.

If I intrepret the datasheet correctly for IC 501, LM25765, pin 5 with 0V indicates ON while 5V indicates OFF.

On IC504, when I was probing, I had the black lead on pin 1 and it slipped and briefly touched pin 2 and I noticed the backlight came on while it was shorted. However, I don't know if there was a display or not because the panel was face front on the carpet.

Quote:
Originally Posted by PlainBill
An obvious next step would be to check the onboard voltage regulators. I count 7 of them.

PlainBill
retiredcaps is offline   Reply With Quote
Old 07-04-2010, 12:26 PM   #6
el3ctroded
Senior Member
 
Join Date: Nov 2008
City & State: NC
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Professional Tech
Posts: 184
Default Re: Daytek DCM-17WT no display

Do you have anything to use to test the CCFLs? 1 may be bad, though it usually will flash at turn-on when 1 is bad... I usually connect 1 at a time to find the bad one.

LCD Monitors also usually will display on the screen, you just can't see it cause of the backlight not being on. Use a bright flashlight and an input with a bright background being displayed to see if you are getting any display on the panel.
el3ctroded is offline   Reply With Quote
Old 07-04-2010, 12:44 PM   #7
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

When I disconnect the LVDS cable, I get a full white screen on solid (not a brief flash). To me, this would infer, both CCFLs are working.

Quote:
Originally Posted by el3ctroded
Do you have anything to use to test the CCFLs? 1 may be bad, though it usually will flash at turn-on when 1 is bad... I usually connect 1 at a time to find the bad one.
retiredcaps is offline   Reply With Quote
Old 07-04-2010, 01:03 PM   #8
el3ctroded
Senior Member
 
Join Date: Nov 2008
City & State: NC
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Professional Tech
Posts: 184
Default Re: Daytek DCM-17WT no display

Don't assume. Test 1 at a time. Looks like you have 4 CCFLs, so it would be hard to tell if just 1 failed.
el3ctroded is offline   Reply With Quote
Old 07-04-2010, 02:12 PM   #9
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

Good point. So I took another LCD panel and tested it in the following manner.

All tests below without the LVDS cable plugged in.

1) Inverter board CN5 connected to Daytek CCFL tube "1" while the other 3 (CN4, CN3, and Cn2) are connected to an external LCD panel.

Result: Daytek LCD panel is white -> CCFL tube 1 works.

2) Same as above, but CN4 connected to Daytek CCFL tube "2" while the other 3 (CN5, CN3, CN2) are connected to an external LCD panel.

Result: Daytek LCD panel is white -> CCFL tube 2 works.

I did the same for CN3 and CN2 and CCFL tube 3 and 4 works.

In all cases, the external LCD panel was white.

However, WITH the LVDS cable plugged in and doing the exact same tests above, I get nothing on the Daytek LCD or external LCD screen.

I'm ready to test more suggestions.

Quote:
Originally Posted by el3ctroded
Don't assume. Test 1 at a time. Looks like you have 4 CCFLs, so it would be hard to tell if just 1 failed.
retiredcaps is offline   Reply With Quote
Old 07-04-2010, 02:24 PM   #10
el3ctroded
Senior Member
 
Join Date: Nov 2008
City & State: NC
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Professional Tech
Posts: 184
Default Re: Daytek DCM-17WT no display

Well, at least we verified the CCFLs. How about seeing if there's any display on the screen using a flashlight?
el3ctroded is offline   Reply With Quote
Old 07-04-2010, 03:09 PM   #11
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

Good suggestion. I tried this with a working DVD player and known good cables and composite/audio outputs.

I hooked it up and cycled through the source button on the remote and front panel and I hear no audio. I tried turning up the volume up/down on the front panel via knob and remote control. I also tried pressing the mute button several times and still no sound.

I found something new that I initially didn't find. With the LVDS cable plugged in, I can turn ON the TV via front panel by pressing in the button, but I cannot turn it OFF by pressing the front panel. I also cannot turn it ON or OFF via the remote.

With the LVDS cable unplugged, I can the TV ON and OFF using the front panel button.

Quote:
Originally Posted by PlainBill
Another trick I use is to hook up an old video game or other signal source with composite out to the composite inputs. Then I step through the inputs until I hear the sound out of the speakers.

PlainBill
retiredcaps is offline   Reply With Quote
Old 07-04-2010, 03:38 PM   #12
el3ctroded
Senior Member
 
Join Date: Nov 2008
City & State: NC
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Professional Tech
Posts: 184
Default Re: Daytek DCM-17WT no display

No display on the panel points to main board being faulty as you originally suspected.
el3ctroded is offline   Reply With Quote
Old 07-04-2010, 05:41 PM   #13
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

Hmm, I missed one variation of this test.

With the LVDS cable unplugged, I can use the remote to turn the TV ON and OFF. Also, with the remote, I was able to switch the TV to composite and hear sound.

Once I found sound and composite source, I powered off the TV, plugged the LVDS cable back in and I saw the TV say something like "Composite Input no signal, monitor going to sleep" and the green power LED turns to red after about 5 seconds.

So I try again. I unplug the LVDS cable and I get audio, a white screen, but no picture. I power off and replug in the LVDS cable and I get no audio, no picture, and no message about a missing input signal.

Quote:
Originally Posted by retiredcaps
With the LVDS cable unplugged, I can the TV ON and OFF using the front panel button.
retiredcaps is offline   Reply With Quote
Old 07-08-2010, 12:46 AM   #14
retiredcaps
Badcaps Veteran
 
Join Date: Apr 2010
City & State: Canada
Posts: 9,092
Default Re: Daytek DCM-17WT no display

Any suggestions on replacing the solder pads? I was doing really well today removing (from another monitor) one FU9024 and two C5707s until one side of the C5707 solder pads all came loose. All that effort installing new components only to have the last C5707 screw up. :-(

I heard something about solder glue as an alternative to solder?

This missing pad looks like another post at (2nd hole)

http://www.badcaps.net/forum/attachm...chmentid=16725

After 10 or 11 repairs, I have only had problems lately with the solder pads coming off. In both cases, the monitors were 2003/2004 heritage.

Quote:
Originally Posted by el3ctroded
The reason you had so much trouble is your soldering iron is likely not powerful enough to heat the part and power/gnd copper planes on the PCB, or there was no flux left in the solder, or both. The reason solder didn't want to stick to the board is the same reason: You were likely not getting the solder point hot enough, most likely due to a too-small wattage iron.

Last edited by retiredcaps; 07-08-2010 at 12:49 AM..
retiredcaps is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 11:37 AM.
Did you find this forum helpful?