Products > Test Equipment
Test Equipment Anonymous (TEA) group therapy thread
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mnementh:

--- Quote from: Robert763 on July 07, 2022, 06:56:09 am ---
--- Quote from: mnementh on July 06, 2022, 07:22:41 pm ---
--- Quote from: Vince on July 06, 2022, 06:48:13 pm ---
--- Quote from: Specmaster on July 06, 2022, 04:24:34 pm ---
--- Quote from: Vince on July 06, 2022, 04:04:32 pm ---TV REPAIR


--- End quote ---
Make sure if you are able to resurrect the other strings, that your friend is well aware that he might actually spot areas of his screen that are dimmer than others, in the areas with the dead LEDs, otherwise he might not be happy with you. Short of replacing all the strings, I can see no way around that problem. Great work so far, keep it coming.

--- End quote ---


Well yes if I manage to fix the thing I will see if the lighting is even enough to be acceptable, i fnot will tell him what he wants to do.

Hopefully there WILL be dark spots and he will tell me OK fuck you can keep it... more spare boards/parts for Vince !  >:D

We shall see.

I don't know where to buy the strings nor how much that costs. If it's available for this particular TV, and is ridiculously cheap including shipping... like 20 Euros shipped, and given the TV is recent, maybe he will want to pay for that. We are not there yet....
--- End quote ---

Why the eff would you trash an obviously repairable TV like that? Just put it away and wait for a paycheck so you can buy some LEDs for Ifni's sake. You really should replace those LEDs anyways, even if you are sending it back to the owner. Just jumpering them out is begging for all the others in the string to fail prematurely.

Correct repair, short of replacing them all, would be to measure voltage drop across every LED with them lit up and replace any that read appreciably lower or higher than the average. That would be your best chance to avoid recidivism. You already have a cheap hot-air rework station, right?

mnem
 :-/O

--- End quote ---

These LEDs are driven by an active constant current source. Shorting out one or two does not stress the other LEDs in the string. It does affect the CC driver but probably not enough to reduce it's reliability.
--- End quote ---

Empirical evidence shows otherwise; I expect it's the startup current or possibly overshoot because of the incorrect number of LEDs vs original design. I'm fully aware that these are driven CC; I explained this to Vince earlier in case he wasn't aware. These are not common LED lighting CC drivers which are designed to handle a "range of LED string lengths" at a fixed drive current; they are application-specific and constantly modulate the drive current to very specific levels dependent upon the video program in order to achieve the multiple illumination zones required for higher "dynamic contrast". I see potential for overshoot, especially if there are other "walking dead" LEDs in the string that still light up but haven't burned out yet.

That's why my advice was to test voltage drop across all of them lit up and replace any that were appreciably higher or lower than the average, if not all at once. Best chance at getting more the original 3-4 years out of the thing. :-//

Cheers,

mnem
 :-/O
bd139:

--- Quote from: Specmaster on July 07, 2022, 10:39:13 am ---
--- Quote from: bd139 on July 07, 2022, 10:25:16 am ---I need to go there again now. Nice photos  :-+

--- End quote ---
Been there, it's a desolate area, very windy and no shelter if the heavens open up, so no thank you.

--- End quote ---

Sounds heavenly to me  :-DD

I went there on the actual mini railway years ago. Not since.
mnementh:

--- Quote from: med6753 on July 07, 2022, 07:16:37 am ---
--- Quote from: bd139 on July 07, 2022, 06:25:21 am ---
--- Quote from: med6753 on July 07, 2022, 12:21:38 am ---
--- Quote from: mnementh on July 06, 2022, 11:26:47 pm ---
--- Quote from: bd139 on July 06, 2022, 09:05:29 pm ---Find an image editing tool with white balance control on it. Click that then click the bit of the picture they’ll at is supposed to be white. Job done. 99% of the photo is the photographer not the camera
--- End quote ---

med uses Winbloze. Windoze Photos works very well for minor post-processing; that pic, I'd just turn the "WARMTH" and "CLARITY" sliders up a click or three; would make a world of difference. Vince complains about my grey printed knobs being purple too; personally, I suspect the monitor he's using injects a wee bit of bloo. ;)

mnem
 :blah:

 

--- End quote ---

No I don't. IrfanView64.

--- End quote ---

I am sorry for your loss  :-DD

--- End quote ---

Gee....seems to work OK for my needs.  :-// :-DD
--- End quote ---

Mmmmhmmmm... like my grand-dad usedta say: "I like to beat my knee with a monkey wrench, cuz it feels so good when I stop." ;)

mnem
*toddles off too...*
Peter_O:

--- Quote from: Neper on July 07, 2022, 10:29:23 am ---Etwas für Kenner or, less positive, gewöhnungsbedürftig.

As to my first photo, I'm still looking for an English translation of Während der Fahrt bitte festhalten. Literally: Please hold on during the ride.

--- End quote ---
Please hold on tight while driving please!

One of the rare occurences of "bitte" in german, so please ...    :-DD
mnementh:

--- Quote from: Vince on July 07, 2022, 07:56:33 am ---
--- Quote from: Robert763 on July 07, 2022, 06:56:09 am ---
--- Quote from: mnementh on July 06, 2022, 07:22:41 pm ---
--- Quote from: Vince on July 06, 2022, 06:48:13 pm ---
--- Quote from: Specmaster on July 06, 2022, 04:24:34 pm ---
--- Quote from: Vince on July 06, 2022, 04:04:32 pm ---TV REPAIR


--- End quote ---
Make sure if you are able to resurrect the other strings, that your friend is well aware that he might actually spot areas of his screen that are dimmer than others, in the areas with the dead LEDs, otherwise he might not be happy with you. Short of replacing all the strings, I can see no way around that problem. Great work so far, keep it coming.

--- End quote ---


Well yes if I manage to fix the thing I will see if the lighting is even enough to be acceptable, i fnot will tell him what he wants to do.

Hopefully there WILL be dark spots and he will tell me OK fuck you can keep it... more spare boards/parts for Vince !  >:D

We shall see.

I don't know where to buy the strings nor how much that costs. If it's available for this particular TV, and is ridiculously cheap including shipping... like 20 Euros shipped, and given the TV is recent, maybe he will want to pay for that. We are not there yet....
--- End quote ---

Why the eff would you trash an obviously repairable TV like that? Just put it away and wait for a paycheck so you can buy some LEDs for Ifni's sake. You really should replace those LEDs anyways, even if you are sending it back to the owner. Just jumpering them out is begging for all the others in the string to fail prematurely.

Correct repair, short of replacing them all, would be to measure voltage drop across every LED with them lit up and replace any that read appreciably lower or higher than the average. That would be your best chance to avoid recidivism. You already have a cheap hot-air rework station, right?

mnem
 :-/O

--- End quote ---

These LEDs are driven by an active constant current source. Shorting out one or two does not stress the other LEDs in the string. It does affect the CC driver but probably not enough to reduce it's reliability.

--- End quote ---

Yes and no. There are 4 strings but the driver has only two outputs, so they wired strings in 2 parallel pairs : string 1 and 2, and strings 3 and 4.  So the chip can only regulate the overall current in a pair but has no clue about how the current splits between the two strings in a given pair. So if you remove one LED then there is an imbalance that the chip can't know about nor act upon.
I assume that's what Dragon had in miind...

In my case I am "lucky" in that I have one failed/bridged LED in each string of a pair, so they still have the same number of LEDs each !!!  >:D

--- End quote ---
Are the strings possibly wired so that the polarity opposes in each pair? This would make for 4 illumination zones.

mnem
 :-/O
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