shield problem for 5 and 7 inch LCD display

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1

Hi, everyone
I want to buy a LCD shield for my LCD, I have a 5 inch LCD and 7 inch one.
Now I want to buy a shield for the two LCD. I mean, the shield must adaptable for the both two LCD.
I found something on eBay.
The first
http://www.ebay.com/itm/TFT-SD-Shield-for-Arduino-MEGA-2560-LCD-Module-SD-level-translation-2-8-3-2-DUE-/121161179201?pt=LH_DefaultDomain_0&hash=item1c35c4e041
They promise that their shield is compatible for all most of the arduino LCD displays.

What make me hesitate is the second
http://www.ebay.com/itm/SainSmart-TFT-LCD-Shield-For-Arduino-Mega2560-R3-5-5-Inch-LCD-Screen-Tracking-/351018277798?pt=LH_DefaultDomain_0&hash=item51ba51dba6

On its "note 3", I found the words
"This shield is compatible for Most style of LCD screen except the 7 inch LCD due to the special circuit structure of 7" LCD. Even though they are similar, you could not distinguish them on your naked eyes. If you need it, please search from our store and Follow the item title."

And then I visit the seller's store, I found a series of arduino LCD displays, 1.8", 2.4", 3.2" and so on. The sold record is also huge.

Whatever, maybe they are also a professional arduino LCD seller especially the LCD kits for mega or uno.

Is it really true that the shield is not compatible for the 7 inch LCD, somebody have used the shield for the both 5 and 7 inch LCD? just because of the resolution?
somebody give me your experience.

2

That shield is the CTE shield. You might be better off going to the ColdTears ebay store and getting the story from the horse's mouth. I have it and I understand it will do a swag of displays right up to 7". I also understand the principle difference is that the larger screens have a higher 3.3v power demand but these shields have an on-board regulator off 5v for that purpose.

The smart move is to get the shield and display from the same source and at the same time, and even then you can stumble. So you might check with the LCD supplier first, if you have already gotten it from somewhere else..