Re: Samsung 460CXN - Power Supply Issue
Nah, no scope available. Alright, I'll get an order together. Thanks so much for your assistance with this. I'll check back in again.
pantherts
Senior Member
Last Activity: 08-28-2020, 07:20 AM
Joined: 03-16-2009
Location: Bethesda, MD
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Re: Samsung 460CXN - Power Supply Issue
Any way to reliably test UP801 in power off mode to see if it's shorted inside?Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Okay, I understand now. That makes sense. Thanks so much for the explanation.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Resistance between source and drain on QP802S is an OL.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
I guess I was under the impression that power flowed from source to drain and then was amplified by the gate activating? I think I was confused trying to follow the positive and negative coming off the BR. I thought we were trying to get it so the BR positive and negative terminals were not showing a short between the two.
Edit: Sigh, Okay so I see now looking at the other mosfet that those two do not have conductivity between them. I guess I was confused as to how a power mosfet actually functions.Last edited by pantherts; 04-19-2018, 01:02 PM.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
So I've removed the QP802S mosfet from the board and confirmed it to be totally shot. Conductivity on every leg to every leg. Now when I test for conductivity between the positive and negative pads where the bridge rectifier are I have an OL. BUT, when I take a wire and stick it into where QP802S Source and Drain pads are I'm seeing conductivity again. Somehow I don't think this is okay.
I've tested the RP824 and RP811 resistors and found them to be spot on at 10ohms each. Correction: DP801 is fine. Still checking DP805.
...Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
R_J,
Thanks! I'll add that to the list to order then, along with more fuses. So what do you think is shorting out after this bridge rectifier?
Edit: Just saw your earlier post with the things to check. I'll check out the two mosfets closer and rp824/rp811 resistors (10 ohm) and the dp801/dp805 diodes. I do think QP802 has an issue though already. Measuring it's resistance in circuit between Drain and Gate is all zero. QP801 reads out at 200ohms Drain to Gate.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
I'm going to have to run for the night, as I have to pick up the g/f. But I'll check back in when I'm home.
Also, as far as NT811S goes, the only spare thermistor I have on hand is a SCK 2R58 (going to have to place an order anyways with digikey so I'll have to add some parts to the list), but I'm not sure what the original part on this board was since it self disintegrated and took some of my vision with it.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Yep, there's continuity there.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Hmm, okay I've removed it and check the resistance between the + and - now completely out of circuit and I'm showing no resistance whatsoever now. I carried on with testing it using Diode check and did the back and forth swapping leads test across it. Readings are only one way:
From Left to Right Testing:
+ to AC = OL
AC to + = 0.460
AC(pos lead) to AC(neg lead) = OL
AC(neg lead) to AC(pos lead) = OL
AC to - = OL
- to AC = 0.466
- to + Resistance is 143 on 200k resolution
...Last edited by pantherts; 04-18-2018, 07:23 PM.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
God I was looking for that schematic everywhere. Thanks so much for supplying that! Alright, so you're talking about the bridge rectifier at BD801S then I'm guessing. That makes absolute sense about the relay RL811S not kicking in without the standby voltage working; I can see the traces heading right on over there that would connect it to all that.
BD801S resistance from + to - is a whopping 0.4Ohms. Checking continuity confirms there's a short here between these two. This BR is toast eh?
Edit: I'm surprised that...Last edited by pantherts; 04-18-2018, 06:39 PM.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Got it. Okay.........soooooo I think I inadvertently found the issue. Kept blowing fuses on the L and N and just had NT811S pretty much explode, so that was fun. Suffice to say I may have more issues than I originally thought now. *Sigh*
Really looking at that RL811S module right now as it's the one that had some funny discoloration around the pads on the bottom of the board.
Any ideas as to where to go from here? :-\
Edit: Also, I do think there's an issue with QP802. Measuring it's resistance between...Last edited by pantherts; 04-18-2018, 06:24 PM.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Both fuses on the L and N lines were bad coming into the board as well as the fuse on the computer's power supply as I assume it blew when the other two blew. Quite a few bad fuses here. Working on finding some replacements. In the meantime I swapped some around and tested voltages. QP801s and QP802s are these ([url]http://www.datasheetcafe.com/sd20n60-datasheet-infineon/[/url]). Not sure if I'm going to be able to test those with this crappy multimeter I have here.
As far as UB801s is concerned, it's a [url]https://cdn.badcaps-static.com/pdfs/77e2f6ea056298c3a3fff7d718dc5d57.pdf[/url]...Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
New development while working at getting this thing connected out of the case so I could test voltages on the bottom of the board. I believe the very first fuse on the board is blown. Are these ceramic fuses? I thought they were supposed to actually break when bad? Removing fuse for testing now.Leave a comment:
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Re: Samsung 460CXN - Power Supply Issue
Thanks for the quick reply Bud! Here's that info you requested:
All pins leading to the main display board are not receiving any voltage whatsoever. I tested the power switch leading onto the board and verified that is indeed working. Whatever is going on here, there's no power making it past the initial power circuit of this thing.
(Saving this listing for later if I need it as I had already typed it up)
Pin 1 (Power On/Off):
Pin 2 (Sync.):
Pin 3 (STB5.2V):
Pins 4-6 (GND):
...Leave a comment:
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Samsung 460CXN - Power Supply Issue
Hey everyone,
It's been a while since I've been here but I'm coming to you with another case to solve as I always turn to the Badcaps Forum to help diagnose these types of things. Alright let's get to it.
This Samsung 460CXN (has a built in Windows embedded PC in it) was found with a bad smell coming from it and no display; it was promptly unplugged and turned over to me for possible repair. Upon opening up the set and carefully inspecting the display's power board (this set has two power supplies, one for the display and one for the computer), I immediately noticed... -
Re: CTX S762G - Some Questions...
I see what you mean. It does look funny but that section of the board is for the audio input to the speakers. I suppose this could be responsible for the main logic chip overheating but I'm not sure. It seems like if that was blown the audio would just plain not work and that's about it. Ideas?Leave a comment:
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Re: ViewSonic VG2021m - DAC-12M033 AF
Just wanted to follow up on this posting to close it out. I have successfully completed the entire repair job. All three devices are working beautifully after 20 capacitors in all being replaced on the three items. The ViewSonic monitor's repair went off without a hitch. The Chi Mei 221D repair went perfectly (after getting rid of all those stupid Crapxon caps). By the way, with the 220us/330uf cap question I ended up going with a 330uf. I replaced all caps with new Panasonic FM caps.Leave a comment:
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Re: CHIMEI CMV 221D won't power up when cold.
Great job Torin! I just did this same exact repair myself! There's a thread floating around here somewhere about it. Enjoy your new(ish) recapped monitor! I know i'm enjoying mine!Leave a comment:
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Re: ViewSonic VG2021m - DAC-12M033 AF
Alright I have quite a few caps on the way. Actually have three projects I'm going to be fixing at once here. A PNY 5700 graphics board, a 22inch Chi Mei widescreen monitor and this 21inch ViewSonic monitor. Not a bad deal considering all were free and the total for the parts was $10. Thanks for your assistance on this. If anyone has any questions on this monitor while I have it open for the next week or so please let me know. Thanks everyone!Leave a comment:
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