Sanyo DP55D44 - Right half of screen darker after thunder storm

[Doc38343]

Sanyo DP55D44 - Right half of screen darker after thunder storm

Next one in line is this odd one. I still need to search for the service manual but i just got it cracked open so i wanted to get it up here to see if any of you have experienced this before... I almost wish it was just dead, something tells me this one may not be easy. I will include a couple of pics of the screen along with the normal rear view.

I will also test voltages and post ASAP.. a little busy tonight, too many irons in the fire...

[attainteddragon]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

looks like you have lost half of your back lights. i would remove the tape off of the bl connectors and get some voltages to start.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

looks like you have lost half of your back lights. i would remove the tape off of the bl connectors and get some voltages to start.

Yeah from the back you can tell the lights are out on that side. I took voltages from CN3 and the one 12v is 11.59v
The next 3 all say 70/24 on/off now on and reads 67.1 all three pins same. there is 3 more wires coming from the plug with tape over it that run to the A main, marked Inverter power and main power.. left to right first wire is 3.29v second is 2.63v third is .0003.
Gonna check the actual back light plugs now far right plug red to white wire reads 133.5v only has the one pair in it. Plug on the left/middle has 2 pairs of red white and both sets read 60.5v Red to white.

I will have to get back on this one tomorrow some time. i am so tired i can't see well. Been a long day. thanks. BTW: electromania did not have the service manual for this one If someone has it handy I'd appreciate it. If it is not the lights themselves I want to repair the board as opposed to replacing one.

Have a good eve folks

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

OK got a few mins here so i tested the LED backlights with the little tester and the side that has 133v lights up fine. the other side lights up but is not as bright and on the tester it settles in at 71v. So I tested the LED jack without the left side (dark side facing rear) middle connector with the two pairs of red white.. and it only reads 61.3v. So with the connector connected it reads 67 but without it connected it reads 61. LEDS light on both pairs (tested separately) with the little LED tester and both equally settle at 71v when bright. (that side is hard to see from the back because of chassis design).

Any ideas on where I could find the service manual for this one P55D44-00 has a little Z8TB in the top right corner of the label. The ones i found are not this model.

Thanks

Meanwhile i'm gonna pull this board and do some testing and examine with microscope.
OK pulled the board and tested all the components and resistors and discovered DD12 a MB515 rectifier is shorted across itself. Luckily it does not go directly to chassis ground. I will try to find a donor and see what happens.
Gotta lay low a bad thunder storm rolling thru...

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

https://www.badcaps.net/forum/attach...6&d=1502764817

Where is the DD12?

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

https://www.badcaps.net/forum/attach...6&d=1502764817

Where is the DD12?

Between the blue cap and the larger orange... it is covering the label slightly.
Just below it is DD13 unused... I have looked at every board i have and none even come close to the voltage rating of that one. i was wondering if they went to a single to save money and if so could i use two in parallel (those pads DD12 and DD13 are parallel for sure) I got very busy and am just now able to even think about it again. I have some 5A schottky diodes but they are only 50v where this one is 100v

It is bad for sure pulled from board to test that

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

That diode looks to be for the boost converter circuit, you have two LED driver circuit on that board, so do not go lower Voltage rating, I would go higher than 100V.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

That diode looks to be for the boost converter circuit, you have two LED driver circuit on that board, so do not go lower Voltage rating, I would go higher than 100V.

Yeah the using diodes in parallel search concurs. more than one can handle more current but the voltage, trigger and all stays the same as a single.

I am going to have to order I guess.. that thing is 150v max rec peak reverse voltage. max rms is 105v max dc blocking is 150v
That is more than triple anything i can find on a donor board i have.
Just when i thought i was going to have a zero cost repair... LOL

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

That diode looks to be for the boost converter circuit, you have two LED driver circuit on that board, so do not go lower Voltage rating, I would go higher than 100V.

Hey do you mind looking at these two data sheets I have this bigger one it is pretty close except the higher voltage, wondering if it would work

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

What are the Voltage ratings of those 4 lytics caps?

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

What are the Voltage ratings of those 4 lytics caps?

the higher up two are 100v, the one near my diode section is 160v and the longer to the right is 200v

Thanks just let me know you thoughts on a sub for that MB515.
I have to go it started storming again and it is getting late i need to shut this spaceship down

Hope to see ya'll tomorrow!! Have a good-un!

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

That means the boosted Voltage is over 100V and they use 100V rating diode, I wonder why it failed!

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

That means the boosted Voltage is over 100V and they use 100V rating diode, I wonder why it failed!

Im going to try this 300v one it is not quite a efficient but I don't think it would fail. I am still quite unsure about substitution of some parts but I hope nothing blows. Grants pass TV has a youtube video where he substitutes a shottkey diode from 600v to 1000v... He said just need to make sure it is fast switching to handle the frequency.
I'll let you know if she blows!!!

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

It should be shottkey diode so the Vf will be lower than normal silicon diode, also the switching speed, otherwise it will run hot and breakdown.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

It should be shottkey diode so the Vf will be lower than normal silicon diode, also the switching speed, otherwise it will run hot and breakdown.

UPDATE:
OK I used the 300v shottkey I had found, it was fast same speed, lose just a tiny bit of efficency (forward voltage drop) but not much. Thermal mass of that board is huge they are using large fields of tinned copper traces on the bottom as heat sink. As a result i got in too much of a hurry and my hot air damaged the capacitor beside the diode... it is a 474 250v and i have done a full crap search of my junk heap to no love... so i have a 474 100v new i decided to put it in to see if it fixes the problem.... I know i can't leave it..... but dude we have a full beautiful picture!
I ordered some 250v 474 that will be here next week, i will put it in a burn her in for a day or two and call it done..

Got to thinking someone may read this and not understand the diagnosis/problem.
The reason that half of the screen wasn't lit is it was not getting full voltage. It was getting 67v on two of the pairs of wires feeding the LED back lights when it should have been getting 80v. The other side was feeding from a single pair using 133v, it was working. I started looking for a partial short or other reason my voltage was pulling low. That is how i found the bad diode on the side that powered the failing LED connector. The clue was that when i had it unplugged from the led's it went lower still to 61v. The diode failing was only letting it get an un-rectified PWM signal (PWM is how they boost voltage from lower to higher in low current situations) the result was limited voltage lower than the need and not enough current to light the LEDs. That part was too near the high limit .. it was rated at 105v and using a variable probably from 80v to 100v or so under normal use. when the thunderstorm caused the lights to flicker i suspect the already stressed diode gave up the ghost. We substituted a larger powered 300v shottkey diode that was very near all the other ratings.. amp, forward, reverse, heat and max peak and TIME ... fast switching to handle the high frequency PWM signal, without getting too hot. Now it reads a solid steady 80v on both pair of LED leads with a normal brightness picture.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

FINAL UPDATE:

New parts came so I was able to put the 250v 474 capacitor back in place.
Been burning in long enough now to call it a successful repair.
Posted a couple of pics of the substituded shottkey diode replacement.
It was double the size of the original but since the pads were parallel I was able to use it by using both and folding the legs back carefully.
Second to last pic is with the original bad diode laying beside the board.

Done.

[tom66]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

It should be shottkey diode so the Vf will be lower than normal silicon diode, also the switching speed, otherwise it will run hot and breakdown.

You will have a lot of difficulty finding a 300V schottky diode. They are out there, but very expensive and in large packages.

It's a lot easier to use a fast recovery diode for these types of application and they usually work fine.

[budm]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

Just keep checking the temperature and find out, but since the current will be <1/2 A so heat may not be the problem.
What is the P/N of that sub diode any way?
BTW, since you have two booster circuit, did you also replace the other one at the same time?
I am sure they compromised on the parts used in the TV just make it lasts long enough to pass the warranty period.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

Just keep checking the temperature and find out, but since the current will be <1/2 A so heat may not be the problem.
What is the P/N of that sub diode any way?
BTW, since you have two booster circuit, did you also replace the other one at the same time?
I am sure they compromised on the parts used in the TV just make it lasts long enough to pass the warranty period.

Yes both the spec sheets are up above.. posted earlier.
It is working great... If there had not been the two pads side by side it would not have worked.
The other one is already a 300v so i didn't mess with it.
Board seems stable and solid... been running it for a good 10 hours.

It was almost like the MB515 was a substitude they used in the factory.. the other one was totally different brand and rated much higher as i mentioned.

[Doc38343]

Re: Sanyo DP55D44 - Right half of screen darker after thunder storm

You will have a lot of difficulty finding a 300V schottky diode. They are out there, but very expensive and in large packages.

It's a lot easier to use a fast recovery diode for these types of application and they usually work fine.

Donor board.... gotta be good for something besides the dump...