Re: Samsung LN52A550 - clicking. Eeprom or something else?
I use the chip quick solder and flux to tin the pad. That reduces the melting temp pretty significantly. Since I didn't have the proper rework air gun I just used a heat gun with a cover with a small hole over the business end. Heat until the pad reflows then you're done.
fireman_bob
Member
Last Activity: 05-19-2015, 05:08 AM
Joined: 05-14-2014
Location: hartfort,ct
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I can't see how. I've replaced most of the parts in that area and re-soldered every connection, including the flash memory chip on the bottomside.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
So I spent a good deal of time over the weekend probing every signal I could on this board with my scope and I do not see any one signal that is different when the board starts versus not starting. There's still that one area that I can cool/heat to control the board startup behavior.
I just can't find the signal that's causing the board to not start. All the data lines at the flash memory and NVM look good so I know the CPU is starting every time, but there's some signal that it's seeing that it doesn't...Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I'm not sure what you mean. I don't believe the EEPROM is bad since the set boots up when its "warm". I've also replaced this chip with no change in the failure mode.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Yes, the AT24C256BN is the correct part. I have a good microscope and I've checked the via's and don't see anything unusual. Is there some other way to check them?Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
That Atmel IC is the main NVM IC204 24C256. I've swapped that with no success (and performed a factory reset after swapping the chip).
I do have freeze spray and that's I've been using to cool it into non-working mode. Then, as you say, using a soldering iron tip, heat the pcb around Q500.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Sorry it's rotated 90 degrees. This is along the top side of the board, to the left of the ribbon cable and just above the metal can over the CPU....Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Changing the caps did not fix my board. When the board is cool, it won't start unless I apply heat in the area or right on Q500. Once it starts, it will restart every time, unless I let it sit and "cool" off.
Along with C102 and C131, I've replaced Q500 and the Caps right above it (C516-518) with no success. At this point I'm wondering if there's a break in one of the inner layer traces under Q500.
Still stumped!!Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Here it is....Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I've located a schematic of a very similar board (from LN46A530) which shows two 10uF/10v caps in parallel on IC101 pin 2 (C138 and C102) and one 10uF/10v cap (C131) on IC102 pin 2. IC101 and IC102 are the same as the board we're discussing.
It also shows the caps I'm looking for (C516-C18). They indeed go to the Flash memory chip.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Capleaker I don't think it's Q500 or the resistor since the input signal is missing when the set won't start. Q500 is on the output side that connects to the NVM. That's just the area of interest. There's also the 4 caps right above those parts that may be bad, but I don't have the values for them and I don't know where they go. The input to these caps comes from a via from internal traces. The input voltage looks solid at 3.3vdc whether the set starts or not. The backside of this area has a part that looks like a DPRAM...Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I think I've narrowed the problem are down to the section around Q500 and R572. When this area is cold, the relay just cycles. When I heat up this area, the TV works. This is very repeatable with freeze spray just on this area and a soldering iron on the PCB in that area.
Q500 appears to control the WP on the NVM 24C256. If I watch the input to Q500, under good conditions it transitions low to high 4 seconds after POR then cycles a few times. When the set fails (is cold), the input just stays low. I'm not sure...Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Heat definitely helps the issue. When I heat the top left over the switching regulators, the set powers on every time.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
That's a good test. I tried freeze spray with no luck.
One thing to add to my list:
Checked all PS voltages at 24 pin connector.
I'll try the heat gun in a while and report back.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I did some poking around with my scope on the 2 regulators on the main board (IC101 and IC102) both with the relay cycling and with the TV working. In both states, both of these regulators appear to be working. I see a chopped output on pin 3 at about the same duty cycle whether the set is working or cycling.
The input voltage on both of them remains steady around 5VDC in both good and bad conditions, so I'm starting to think the problem with my board is not around these regulators. That would explain why adding capacitance...Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Hi Budm,
I did try paralleling both caps with 68uF/10v and it made no difference.
I used some tantalum caps that I had around, but they probably aren't low ESR. I don't have any 100uf/10v low esr here.
I should have my parts from Mouser in a few days.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
If you scroll about 1/2 way down the screen you should see
"Manuals and Downloads". Under that and to the right it should say "Downloads".
Under that is a link to a pdf and a "See More +" link.
Do not have that on your screen?Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Your link is not correct. Use the one Budm specified.
[url]http://www.samsung.com/us/support/owners/product/LN52A550P3F[/url]
I upgraded my firmware but the problem still exists. I've ordered 2 new switchmode regulators and the caps. Hopefully they will solve the problem.
Thank you Budm for all of your help!!
BobRe: Samsung LN52A550 - clicking. Eep...2A550P3F[/url]Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
I just got it. Click "See More" under the PDF under downloads.Leave a comment:
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Re: Samsung LN52A550 - clicking. Eeprom or something else?
Mine is 2008. Do you have any info for this model year?Leave a comment:
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