I have got an old Gardtec GT595 alarm which has got a faulty keypad with a failed LCD screen. This was apparently a very common problem with these and many people have had to replace the whole alarm because of this problem. Somebody claims to be able to repair the keypads by replacing the screen and I have tried it myself by replacing the LCD with a commonly available HD44780 1602 16x2 Serial LCD screen but it is not working. I am sure it is a problem with a driver or simular which is not allowing the screen to talk to the rest of the electronics. Does anyone know what this original screen was and what replacement screen and driver it might need? Working on 16x2 screens is new to me.
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Dunno what he does to it, but for some reason after the repair the GTAG does no longer function. Wonder why?
The 4 wire keypad LCD display can be repaired but the GTAG Will no longer function
The 6 wire keypad LCD display can be repaired but the GTAG Will no longer function.
Repair models include 595 600 490 490x and 800 series -
the display is a regular parallel interface display,
you can get them in lots of colours but also different payouts.
so if you buy one on aliexpress or wherever, make sure it's got the same hole spacings for the screws and the connector is the same.
yours has the connector as a single row top-left, you can also get the with the connector on the bottom or as 2 rows on the side.
but electrically theyare all the same.
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maybe show us what it connects with?
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Here are some more photos of the keypad. It is very hard to find a reasonably priced working keypad for these alarms. It is put me off buying another Risco alarm. I am not very happy that the engineer locked their own code into it as well so would install one myself next time.
When I tried replacing the screen on this one, I disturbed a very small bit of glue holding the G-Tag wiring and the G-Tag now no longer works so it is something to do with the effect that it has on the coil.
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check the display is getting 5v
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What controller ic chip does it have on the main board
It has been my experience that when you have LCD screens controllers are not the same even if they are the same model number you have the LCD command loaded on the controller for it to work correctly
Because one time I was doing a microcontroller with a LCD screen controller display that I had not used before and because the routine was not run every time you turn on the device it would not display any thing at all but once I complied the program again now it shows up on the new LCD screen this could be issue hereComment
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The main difference between these LCD displays is the how the LED backlight is done. What pins for it, dropping resistor etc.
What happens when you rotate the contrast trimpot? You should see the pixels darken... or lighten.
Wait - is that a display heater or some nutty LED backlight in your pics? To "A1" "A2".Comment
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The wire coil that connects to A1 and A2 and goes around the LCD is the pick up coil for the G-Tag. I suspect that there is some kind of driver issue with this with the driver being loaded into one of the chips that are located underneath the LCD. I think I have gone as far as I can with this project without knowing more about how that LCD screen talks to the rest of the LCD board.Comment
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well - now you know
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Thanks. After reading this I can seen that the LCD has to be programmed which is what the problem is as I am only getting a single line of black blocks from it.Comment
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programmed?
it's a passive device, you just write the text to it together with stuff like position.
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