Samsung 40" mystery


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Samsung 40" mystery

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bcarroll_us
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Jul 23, 2016, 10:57 PM

Post #1 of 8 (1424 views)
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Samsung 40" mystery	Can't Post

I have a model LN40A530P1F with model code LN40A530P1FXZA.

The tv worked fine, then suddenly one day would not power on and was making a loud beep/high pitch sound. The red power light is also just steady blinking. Tried to unplug and replug into 110v, same issue. Did research and found a common power supply capacitor issue. Examined my caps, but they looked good. To be thorough I replaced them, but no improvement. To rule out that a transformer or unseen resistor or other diode problem I bought a full replacement power supply. Still no change. While talking to that supplier's customer support, they asked me if I could see any back lights. I took the tv into a pitch black closet to be sure I wasn't missing anything, but there's nothing but the blinking power light.

I can add that if I leave the tv plugged in for 10-20 minutes It will give a long loud beep. One time it gave a beep then a loud sound, like static (or white noise) on older TVs when there is no signal. Before I continue spending money trying part after part I hope I can find someone with more experience with these devices that may know exactly what is happening.

Thank you for any help or troubleshooting suggestions!

jts1957
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Jul 23, 2016, 11:36 PM

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Re: [bcarroll_us] Samsung 40" mystery [In reply to]	Can't Post

CN801 & CNI803 connector pin voltages.

Measure TWICE - once with the set plugged in leaving POWER button alone (Standby mode). And once after ONE press of POWER button. You may have to repeat power button press for each pin measured.

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Location: Far, Far Away

bcarroll_us
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Jul 24, 2016, 5:01 PM

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Re: [jts1957] Samsung 40" mystery [In reply to]	Can't Post

Hi, thanks for the suggestion.
I just started taking these measurements by unplugging the ribbon from the main board (so the cable is still plugged into the power supply), but realized once I got to the measurement after one press of the power button, that there is no functionality when that cable is unplugged. Obvious in hindsight. I'm going to plug everything back in and try to take the measurements from the back of the power supply board, but I thought I'd note that I only got voltage on 1 pin using this first method. Pin 3 on CN801 had 5.08vdc (labeled "stb5.3v"). Everything else was 0.
I also wanted to double check to be sure that taking the measurements from the board with both cables plugged in was in fact the correct approach.

I'll post the aforementioned numbers when I can get back to working on it after lunch.

Also, this time after leaving it plugged in for a while, the sound was like a rapid beeping with slight static. I'll try to time it next time and possibly video the next noise if it will be of any use.

(This post was edited by bcarroll_us on Jul 24, 2016, 5:22 PM)

jts1957
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Jul 24, 2016, 5:46 PM

Post #4 of 8 (1404 views)
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Re: [bcarroll_us] Samsung 40" mystery [In reply to]	Can't Post

No need to unplug connectors or disassemble boards from chassis frame. You should be able to 'back-probe' the wires of the cables that plug into those connectors.

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Location: Far, Far Away

(This post was edited by jts1957 on Jul 25, 2016, 2:29 AM)

bcarroll_us
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Jul 24, 2016, 8:01 PM

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Re: [jts1957] Samsung 40" mystery [In reply to]	Can't Post

I don't know why I'm trying to make everything so hard today..of course I should back probe. Thanks for that.

I've posted two clips to YouTube of the phantom sound.
https://youtu.be/mwhvoZvUD8Y
https://youtu.be/J1qx7b4lYng

One other detail is that heat sinks hs803 and hs804 got warm to the touch, while there was no noticeable change to hs801 or hs802.

I took the voltages as instructed. The measurements did not change after the single press of the power button. To be thorough, I went back and did a third reading pressing the power button twice on each pin. No change there either.
The voltages are as follow:
CN801
1-4.3
2-1.57
3-5.08
4-0
5-0
6-0
7-12.92
8-12.92
9-0
10-0
11-0
12-0
13-5.06
14-5.06
15-5.05
16-5.06
17-0
18-0
19-12.93
20-0
21-12.93
22-12.92
23-0
24-0

CNI803
1-0.02 (changed the scale and got 33.1 mV)
2-1.9
3-2.7 (but this one jumped around up to around 5v before settling at 2.7..almost like a capacitor maybe)

4-0 (ground)
5-5.06

Again, I'm incredibly appreciative of your help and patience with my lethargic brain today.

jts1957
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Jul 24, 2016, 9:02 PM

Post #6 of 8 (1398 views)
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Re: [bcarroll_us] Samsung 40" mystery [In reply to]	Can't Post

Pin 3 on CN801 should be there at all times. The other DC voltages should come and go as the set is turned On/Off.

IF all DCV stay up all the time AND Inverter On/Off (CNI803 Pin 1) isn't toggling as set is turned On & Off, I'd suspect Main Board is bad.

As far as noise(s). Where are sounds coming from? Speakers? a part on a specific board?

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Location: Far, Far Away

(This post was edited by jts1957 on Jul 24, 2016, 9:50 PM)

bcarroll_us
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Jul 25, 2016, 2:21 AM

Post #7 of 8 (1388 views)
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Re: [jts1957] Samsung 40" mystery [In reply to]	Can't Post

Ok, thanks for that diagnosis. Is there a reliable source for replacement boards that I would have access to as a consumer, or will eBay be my best bet?

The noise is coming through the speakers. I've noticed, especially today, that each time it's a little different (you may be able to notice in the videos).
https://youtu.be/mwhvoZvUD8Y
https://youtu.be/J1qx7b4lYng

(This post was edited by bcarroll_us on Jul 25, 2016, 2:44 AM)

jts1957
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Jul 25, 2016, 2:45 AM

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Re: [bcarroll_us] Samsung 40" mystery [In reply to]	Can't Post

Pretty much a crap shoot. Cheapest price is not the first criteria you should be concerned with.
Make sure the seller has good reputation / return policy / more than one of the item you need, etc.

The solder joints on Ball grid array ICs have been known to cause many strange symptoms.
Many sets may use different variants of a board, so make sure you order the correct one.

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Location: Far, Far Away

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