Samsung LED DLP HLxxA750A1F easy fix - AVS Forum
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post #1 of 11 Old 11-30-2011, 06:15 AM - Thread Starter
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Ok, I had been testing my power supply mod to fix random power up issues. Parts list at the end.

I had noticed at times my DLP had powered on and off or just had the light flash without producing any picture or startup sound.

As of late I found that the power supply's heating up issue was because of the 12V 2.5A output was being consumed to the point of not keeping up with demand once fully warmed up.

The culperate can be easily found on the bottom side of the Main Board. If know how to solder components, the fix is about $30.00 for all the parts to repair your power supply and faulty main board components.

That is less than the cost of replacing both at over $325.00.

Samsung had used low cost filtering capacitors in the power supply and revised a critical component change to the power supply in various areas.

What happens is a snow ball effect, filtering capacitor fail, causing higher spikes to hit and weaken the pancake capacitor at the end of the filtering stage.

The only way to know is to sniff for a slight odor of ozone or BBQ affect when the power supply has warmed up. Once you determine there is some odor. Power off and wait a few minutes before removing the power supply. The rectangle box things are the poly film capacitors. They are along side the toroid (doughnut shaped) filters. Remove each one and look on the bottom ends for discoloration. Not all will be discolored but might as well be replaced as they have been stressed.

Once the pancake capacitor becomes too weak to filter, voltage spikes will be introduced into the output stage randomly.

Because of a design change to put the pancake capacitor at the end not the beginning near the fuse, and not to follow Fairchild's design guidelines in using proper filtering capacitors for the FSCQ0765RT TV switch to power the DC switched power to the main components.

As for the Main Board, this part is speculation about the parts used in the main board, but has truth to more low quality parts.

There are two 470 Ohm 1/3w chip resistors powering a LM317 1A adjustable voltage regulator that is to deliver 6.3v to the main controller chip of the Main Board.

Mine were fried because of the voltage spikes, as they were used as surge protection. They were to fail like a fuse, but actually started to short out below the 150 ohm range. Thus over driving the current capabilities of the 1A LM317 and making it unstable. Mine seemed to become damaged as once it heated up it ran into thermal breakdown causing more and more current to be consumed, and the 12v voltage from the power supply would drop. Because of the higher amount of current the power supply would heat up beyond its normal running temperature.

It was easy to spot without any tools, as it discolored the circuit traces at the resistors and made a blue tent, almost like someone marked the components for QC check.

==================================================

Ok, here is what I accumulated for replacement to keep things tip top. Just because one component will fail, it is best to replace everything associated with the failed components function that could become stressed.

1x xxxxx - 1A 8.2v Zener chip diode, location DZ209
1x LM317EMP - 1A adjustable regulator, location IC204
2x ERJ-P08J471V - 470 Ohm 1/3w anti-surge chip resistor, location R232 and R233

1x B32620J681J - 680pf film capacitor for PS, never was installed, location C8110, between main transformer and black heat sink.

3x B32620J471J - 470pf film capacitor for PS, never was installed, location CS811, C823 & C827, all next to the rear heat sink back side.

2x V275LA20CP - 275VAC 5KA @ 473VAC 145J MOV (Mount them behind input plug between chassis ground and hot & ground wire connections)

2x R46KI368000P0K - 0.68uf 275VAC Poly Film Capacitor, location CX8035 & CX8015

1x PHE840MD6680KD18R06L2 - 0.68uf 275VAC Poly Film Capacitor, location CX8025

Yes, my 2010 Panasonic 42C2 performs better than an S2 No floating blacks and keeps the lowest black levels.
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post #2 of 11 Old 11-30-2011, 08:17 AM - Thread Starter
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Below is the three poly caps that filter in the power supply. Note the middle one, it is discolored on the bottem side. Clearly different than the others. Replacement of all three is recomened.



Below is the location on the bottem of the main board for faulty components than need replacement only if the board is discolored as shown.





Below is where you can find the optional poly cap install locations.


Yes, my 2010 Panasonic 42C2 performs better than an S2 No floating blacks and keeps the lowest black levels.
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post #3 of 11 Old 12-01-2011, 11:32 AM
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Thank you for posting the information. Would it be correct to assume that replacing two 470 Ohm 1/3w chip resistors should fix the symptoms? Other replacement parts are recommended as preventative measure?

I am not sure how much longer I would want to prolong the life of this TV, prior to replacements of other aging/expensive parts, but if replacing two resistors can prolong and correct the powersupply function for next 3 more years, I'll vouche for a simpler patch.

Thanks again for sharing your experience.
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post #4 of 11 Old 12-02-2011, 06:12 AM - Thread Starter
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Quote:
Originally Posted by bitemymac View Post

Thank you for posting the information. Would it be correct to assume that replacing two 470 Ohm 1/3w chip resistors should fix the symptoms? Other replacement parts are recommended as preventative measure?

I am not sure how much longer I would want to prolong the life of this TV, prior to replacements of other aging/expensive parts, but if replacing two resistors can prolong and correct the powersupply function for next 3 more years, I'll vouche for a simpler patch.

Thanks again for sharing your experience.

Its all up to you... I just figured most people will want to do it right the first time. For me, I know better. Along with the resistors failing, the Zener diode on the opposite side also is in need of replacement, as I listed it in the required parts.

Gosh, this tv should last 15 or more years easy. I gone through alot of the design and in my maintanence, and found things well thought out just poorly implemented. Like the DLP chip needed heat sink compound as the pad was not the best at transfering to the heat sink. Also the power supply in need of a proper update.

As for wanting to replace in 3 years, so far I can't see much of an improvement in picture until WQXGA becomes reality. Which could be about 15 or so years down the road for the USA. Seems now many stations are now broadcasting in 720p or being up converted properly for HD content. Though there are still alot of older content that is of poor quality upconverting.

IMO the powersupply is the problem for all the issues people have reported with this tv. Unfortunately Samsung revised a few things with the power supply and along with that, some of the components used in the power supply were not the best quality. Outside of the toroid filters, the filtering components are cheap and weak.

For myself my DLP tv is calibrated and performs better than Plasma IMO. I dont like the new Mits as it is does not have perfect lineararity like my Samsung. Since the lineararity issue is from the thin design. Its about 7 inches thiner than my Samsung.

What troubled me is the components in filtering and the revision change, if Samsung would have spent lets say $5.00 more per tv. There would be hardly anyone complaining about Red LEDs failing, DMD issues or the failing to power up issues.

I trusted Samsung too much in the begining, I could have noticed more about this much sooner and would have done a few things to make the power supply better protected as I took note of its design weakness in my earlier thread during my cleaning and maintenance.

Yes, my 2010 Panasonic 42C2 performs better than an S2 No floating blacks and keeps the lowest black levels.
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post #5 of 11 Old 12-03-2011, 08:14 AM - Thread Starter
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Simple, each manufacturer has their own color scheme. The outside shell can be white, grey, green, blue, yellow, or orange. The epoxy that is used to seal can be white, grey, green, black, or red. If you have two different poly caps of the same manufacturer they are usually identical in looks outside of package size. It is rare to see two different poly caps from two different manufacturers to have the same color scheme.

I do prefer white epoxy bottomed poly caps like the ones Samsung used, as they are easy to detect for failure just by looks. But you're only given what is available for sale at any given time.

Yes, my 2010 Panasonic 42C2 performs better than an S2 No floating blacks and keeps the lowest black levels.
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post #6 of 11 Old 12-08-2011, 11:48 AM
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Quote:
Originally Posted by Low Tech View Post

Gosh, this tv should last 15 or more years easy. I gone through alot of the design and in my maintanence, and found things well thought out just poorly implemented. Like the DLP chip needed heat sink compound as the pad was not the best at transfering to the heat sink. Also the power supply in need of a proper update.

Thank you to infinity for posting all of the above info.

Question: When you remounted the DMD heat sink using thermal compound, did that introduce any mounting/seating issues?

After removal of the factory thermal pad, was the installation of a copper shim required to take up any slack? ...Or will the heat sink base rest flush against the DMD chip's surface?

Just have to be sure that removing the thermal pad won't lead to a spacing issue.


BTW, thinking that it would probably be a good idea to remount the LED heat sinks with a superior thermal compound. I'm still "old-school " and tend to prefer AS5. Curious to know what your favorite t-grease is?
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post #7 of 11 Old 12-12-2011, 08:31 AM
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Quote:
Originally Posted by KewlK View Post

Just have to be sure that removing the thermal pad won't lead to a spacing issue.

Alright, I'll answer my own question. Last night I remounted the DMD heat sink using AS5. Since the thermal pad was paper thin, it did not lead to a spacing prob after removal.

Comments:

The factory installed thermal pad was terrible at conducting heat. Before pulling the heat sink, I was curious to see how warm it got after a minute of on-time (fan detached). The heat sink stayed at room temp, how horrible. Then after remounting with AS5, there was noticeable warm-up of the heat sink almost immediately. I highly recommend getting rid of the junky thermal pad...it's worthless.

It that wasn't bad enough, the heat sink itself is made of cast pot metal (zinc alloy). ...Nowhere near as good heat conduction performance in comparison to aluminum or copper. You would think that the DMD chip (being such a critical and expensive component) deserves a better cooling solution than that?

True that the DMD seems to be a very low-wattage IC, but under the right conditions I'm sure it can get rather hot. Reports of the numerous "stuck pixel" failures strongly confirm this.
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post #8 of 11 Old 12-15-2011, 01:53 PM
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Geordi,

Thanks for the great write up on the PS fix. Now, mind posting what that PS looks like with that capacitor installed at location C8110? Did you happen to take a picture of that as well?


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post #9 of 11 Old 12-15-2011, 02:47 PM
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Great addition!
Quoted and added to the repair sticky.

Abundant OTA television is what makes this country different from all others. Lets keep it this way.
The Internet is no place for streaming video.
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post #10 of 11 Old 12-16-2011, 07:52 PM - Thread Starter
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Quote:
Originally Posted by Lee Bailey View Post

Geordi,

Thanks for the great write up on the PS fix. Now, mind posting what that PS looks like with that capacitor installed at location C8110? Did you happen to take a picture of that as well?

Lee, nice to see you checking my thread. I guess it be my contribution to your great work with calibration.

As for location C8110 it may be CS110 as some capacitors are labeled with CS or C designation before the number. I have done some major modifiing since my post, so to recall... I do believe it is along side the large resistor which is center and between the long silver colored heat sink and black heat sink.

In my modding, I ended up cutting and removing the most of the lower section (I left about an inch for the connector and mounting), to make room for a more advanced separate power supply for distributing voltages to the main board and DMD. As all voltages will be isolated.

It is overkill for most, but the power supply I have to modify is free so might as well give it try.

So I waisted $7.00 in updating the lower half of my power supply, but did cover filtering components that were not installed for those who don't mind taking the time to perform the option. Though I do recomend to check the filtering capacitors as stated every year or two as all filtering components will breakdown even sooner with brown outs and dirty power even when the tv is off.

I am modding a small ATX computer power supply that runs @ 450khz switching to run as a separate unit for providing Standby 5v, 5.6v, 12v, and 16.3v to the main board and DMD.

The one I am converting has a quiet thermal controlled fan so it will operate like the OEM and will be mounted as a push fan at the tv input side of the service cover.

Yes, my 2010 Panasonic 42C2 performs better than an S2 No floating blacks and keeps the lowest black levels.
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post #11 of 11 Old 12-18-2011, 03:55 PM
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Low tech,
Any chance you will make this mods (for a price) for the less electronically skilled?
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