Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Please excuse my ignorance about circuits, but when you refer to "in the circuit", are you talking about in the pdf (which figure) or another diagram? I attached pics of the top and bottom of my boards. It would help if you indicate which is which. I don't see a resistor connected to the large cap, at least what I would recognize a one.
If the diode is on the bottom of the board, D103, I have 99 ohms each way. If on the top of the board I have a D101 and D102. D101 I get nothing in both directions accross it, D102 I get a short beep with no reading but I can flip the leads and get the same result, a short beep. I am not sure what I am seeing.
Need help DCLCD 19" LCD Monitor - I already replaced caps
Collapse
X
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Check with and ohm meter out of the board, or in the board? Hot or not?
In the board I see resistance but not shorted. I should be able to check voltage on each post by making a probe tip to reach in there.
Also, I can not get to the SMPS control chip while powered up to check it as in the other thread.
The fluctuating voltage of 10-15V across the 22uf cap indicates that the power supply is trying to start up. Refer to the datasheet application circuit, page 14 regarding the following:
With power off and monitor unplugged,
1) The circuit shows a 56Kohm 1W resistor (your value will be different) connected to the output of the large cap. Find and measure the value of this resistor.
2) In the circuit, you have a 1N3613 diode (your values will be different) feeding the 10uf cap. Locate this diode and check it for shorts.
3) Measure resistance across pins 5 (gnd) and pin 7 (vcc) of the SG3842.
4) You've already checked the mosfet and replaced the small cap.
5) If the above checks good, I have some reservations about the voltage fluctuation on the 450V large cap, you might consider replacing it.
6) If the above checks good, I'm leaning towards replacing the SG3842 chip. It also goes under the part # UC3842 and is dirt cheap, so buy a couple of them.Attached FilesLast edited by jetadm123; 01-03-2011, 09:03 PM.Leave a comment:
-
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Check with and ohm meter out of the board, or in the board? Hot or not?
In the board I see resistance but not shorted. I should be able to check voltage on each post by making a probe tip to reach in there.
Also, I can not get to the SMPS control chip while powered up to check it as in the other thread.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
hi, can anyone tell me what the original uF and voltages are on those four caps c114 115 117 and 118 on the LM004 Ver:3 board... thanks
i had replaced the caps a long time ago with caps of higher uF and voltage ratings... and now those went bad after a few years... and i have no idea what the original specs were..
117 and 118 are 10V -1200uF
Is the yellow square transformer looking unit the SMPS?Last edited by DJM_PHX; 01-03-2011, 05:31 PM.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
In the board I see resistance but not shorted. I should be able to check voltage on each post by making a probe tip to reach in there.
Also, I can not get to the SMPS control chip while powered up to check it as in the other thread.Last edited by DJM_PHX; 01-03-2011, 05:24 PM.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
hi, can anyone tell me what the original uF and voltages are on those four caps c114 115 117 and 118 on the LM004 Ver:3 board... thanks
i had replaced the caps a long time ago with caps of higher uF and voltage ratings... and now those went bad after a few years... and i have no idea what the original specs were..Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
I have the same smps chip in my monitor. Once I replaced the small cap, I got secondary voltages. See
https://www.badcaps.net/forum/showthread.php?t=9904
for details. If the power mosfet is okay, then the SMPS controller may be bad. Replacements are available on ebay.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Have you had any time to put a check list together of what I should do next?Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
There's a mosfet mounted on the heatsink directly below the large cap. I suggest you check it for shorts.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Yes. Screws in and tight.Leave a comment:
-
Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
I appreciate it. The large cap V is the same and fluctuating as before. I read that the Chengx brand is not liked. I can try to get a replacement for it. Since I see the same voltages and fluctuation, I for now will leave it in. The board is looking a bit rough at the solder points.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Any chance of getting the Rubycon? Most here will question the Chengx brand even though the little cap may not root cause here.
If it is not the small cap, please re-measure the large cap to see if the fluctuating voltage is there or not. Other possibilities is that the SMPS controller chip is bad. I'm trying to guide you through each scenario one at a time.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
retiredcaps, and all, have a Happy New Year.
I'm calling it a day and will pic this up next year. But, if you think of anything else, let me know.Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
They were suppose to be Rubycon's but they sent Chengx.
The voltage is not stable and is 10V-15V DC.
Is the large sqr. yellow unit the SMPS?
Why can I detect voltage on the heat sink by the large cap?Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
What is the voltage across the new small cap and is it stable or fluctuating like before?Leave a comment:
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Ok. In post #2 on the right circled in green is the power filter caps. behind them are two units connected to the heatsink (in Yellow). Are they power transistors? The top one, on my board, the outer 2 to the center pin only have 0.1 ohms res. The other two have on the board have much greater amounts. That one is directly connected to the large yellow transformer, or is this the SMPS?
I have not even a flicker of light from the power LED on the front panel any more.Leave a comment:
-
-
Re: Need help DCLCD 19" LCD Monitor - I already replaced caps
Before replacing the big one, what is the voltage across the 22uF cap?Leave a comment:
Related Topics
Collapse
-
by momakaNormally, I never post repairs this quick after I do them, because… I am usually very slow.
But today, I’m making an exception here. Why? No idea. Perhaps only because the repair details are still “fresh” in my head… which is ironic, given this is a 16 year old monitor that hardly anyone will care about today. It is new to me, though.
I picked it up last November from someone on my local Craigslist. It wasn’t very close to where I live, but was close to a family friend that I had to go visit anyways. So after watching the posting on Craigslist for a few weeks and seeing it getting...
-
Channel: Troubleshooting Computer Displays
-
-
by black6hostGood day!
I have a Samson Resolv studio monitor that has no sound output. I've opened it up and found two caps that are bulging on what I believe to be the power supply section of the amplifier board. The board is marked Resolv 65A AMP V1.2. The caps in question are YUSCON, 2200uF, 35V, 85C temp and have markings of RA(P) and are 16mm x 25.5mm tall. I've attached the schematic and the caps in question are C5 and C6. I'm assuming they are low esr caps. I've tested both caps and they test low uF, nowhere near 2200uF.
I'm going to replace the caps and I'll be the first...-
Channel: Troubleshooting Audio Equipment
-
-
by momakaI know I've been a little scarce lately (like the last 2-3 years), but I'm still here and still doing my thing with fixing PSUs.
For today's considerations, I have a Seasonic B12 BC-550 [A551bcafh] 550 Watt ATX power supply for you (click on links for full size images).
https://www.badcaps.net/filedata/fetch?id=3591771
https://www.badcaps.net/filedata/fetch?id=3591772
It's a modern ATX unit with fixed (non-modular) cables and an 80-plus bronze certificate. Here's the label:
https://www.badcaps.net/filedata/fetch?id=359177... -
by momakaHere's another LCD monitor repair: Westinghouse L2210NW.
Quick specs: 22” CCFL backlit LCD, 1680x1050 max resolution (16:10 aspect ratio)
I got it with a bunch of desktops PCs from a repair shop that was trying to free up space a few years ago. It seemed like a cheap monitor, so I didn't really care that much at first when I picked it up (and indeed it is, picture-wise.) But hey, free is free, so I can't complain. Moreover, it looked clean and the screen didn't have any significant scratches or blemishes.
Pictures of the monitor outside/case after a brief...-
Channel: Troubleshooting Computer Displays
-
-
by zlr8rHey guys, bit stumped with this laptop after replacing 2 blown components i.e., MP86493, MP2979A.
To begin with, this laptop was dead-dead.
Now with replaced (visibly) blown components, i do get some progress; after connecting battery or main cable;- am getting white power led
- 5-long-flashes on CAPS Lock and NUM lock
- then, fan full speed
- CPU heats up some (smaller die PCH, does not)
- always constant black screen no matter what's tried
- no USB recognition
- no HDMI output
I tried... - Loading...
- No more items.
Leave a comment: