S825 backlight fix?

[luch]

I thought I heard someplace that there is a fix (resistor or??) for the S825 control head. I have a real nie unit that seems like it is going dim, or so I think. I am still learning the GE equipment, so I am not to sure my way around just yet! I don't have a manual or anything, but if someone has some ideas, or a fix, please let me know?

[vcaruso]

I would sure like to find a quick fix one of mine has a fading display thats driving me absolutely nuts.

[n_zero_ndp]

I would sure like to find a quick fix one of mine has a fading display thats driving me absolutely nuts.

Are you folks talking about poor backlighting or faded segments (or both)???

There is a fix for faded segments if your display board LCD has the metal retainer (old versions had a plastic one that could not pull the display tight enough against the display board).

[vcaruso]

I am having both problems one head has a fading display and the other has a fading backlight

[n_zero_ndp]

I am having both problems one head has a fading display and the other has a fading backlight

Vince, The "bad segments' issue is very common. I have made the repair for at least 2 "BatLab" members to date (firemanbatt & talviar).

I will apologize for the lengthy reply now, but I won't need to tell anyone how to do this repair again with it here in black & white

A total disassembly of the head is required to see if you can fix the faded segments issue. Once you find out if your LCD retainer is metal or plastic, you can proceed with an attempt to fix it (it doesn't always work the first try - sort of a hit & miss type of thing). The more repairs you have under your belt, the better you will get at it

As previously stated, you are up a creek if you have the plastic LCD retainer (it belongs in the dumpster).
If you have never disassembled one of these heads before, be prepared to have a 5/32 allen wrench to remove the 4 screws that hold the back half to the front. The I/O board is mounted to the back-half & has a ribbon cable that attaches it to the front half (processor board). Just unplug the ribbon cable & set the back half aside.
Now remove the 6 screws that hold the thin metal plate over the processor board (these screws might be slot heads or T10's - I have seen both used). Now remove the processor board by gently prying it up from the upper left hand corner (there are 2 arrows on the board pointing to this area). It will come off fairly easy with a bit of prying on the right hand side. Now you are at the last set of 6 screws to remove (should be 7/64 allens) to get at the display board. Once these are removed, the front panel will fall out with the display board.

Yes, you have to go through all of this just to see if your LCD has a plastic of metal retainer. With the front panel/display board face down (components face up) you can see what type of retainer is used. There are 4 slits in the display board where the LCD retainer attaches to the board. If it is metal, you should see 4 black metal tabs bent over against the board thru the slits. If it is plastic, you have no option but to somehow find the metal replacement.

A metal LCD retainer is the key to the fix. The plastic retainer cannot ever hold the LCD tight enough against display board to make 100% electrical contact. If you have a metal retainer, proceed to peel the display board away from the keypad membrane (they are just pressed together at this point). While you have it all apart, it is a good idea to clean up your keypad membrane. I have even washed them with soap & water to get the donut crumbs scrubbed off of them Now, check the keypad membrane contact side of the display board for grime (if the head has never been apart before, there is sure to be something to be cleaned from this area).

Now for the easy part (ha..ha..): the actual fix for the bad segments... Gently pry the tabs of the retainer up off of the component side of the display board with a small flat blade. Please note the LCD makes contact with the pc board thru 2 zebra strips & the LCD needs to go back into place the way it is removed (meaning it has markings to indicate right-side-up). After the retainer is removed, the LCD might still be stuck to the zebra strips & the pc board. It won't take much to pull it all off of the board. Now peel the zebra strips off of the LCD. Check them for any dirt, etc as it is very critical that they are clean. The area on the LCD where the zebra strips make contact should be cleaned with alcohol & the area of the pc board that makes contact with the zebra strips needs to be cleaned with a pencil eraser. After everything is cleaned up you can reassemble the retainer/LCD/zebra strips combo to the display board. Kinda tricky but the best way I have found is to put the retainer face down with the LCD in place then carefully put the zebra strips in place. The big trick is to now gently set the pc board back down onto the retainer without all of the pieces getting knocked out of place. Several attempts may be required before you get it back together...... The key to this whole repair is getting the retainer tabs bent back down onto the board with as much pressure as possible. You need to hold the board down with one hand pressing hard enough that the board will even flex slightly (don't over-do it!) while bending each of the 4 metal tabs back into place with the small flat blade. This is the part that may have to be repeated several times because if you do not apply enough pressure to the display board while bending the retainer tabs over, your display will still have bad segments.

BTW: you do not need to totally reassemble everything to check out your repair... just a couple screws to hold each board in place then you can plug the ribbon cable into the front half without any assemble to check your display.

I hope this ramlbing will help... otherwise I am available to make the repair for you.

Good luck

[vcaruso]

Thx Ken
I'll give it a try over the weekend.

[n_zero_ndp]

There is also a way to set the intensity of your backlighting... in 4 steps I recall. Just don't remember how. I suppose your photo resistor? light sensor could be going bad on the display board?!?

LBI-38244F may shed some light on it. The KEYBOARD Self Test routine is described in there. Pressing FNC & ADD at the same time puts you in the test mode.

[luch]

WOW! That sounds really time consuming! Oh well, not like I never tried projects like that before. I am sure I have the plastic retainer.....just usually works like that. I did not know the segments were a problem, but I think I will go through the process anyway. The backlight has a photocell? Maybe that IS the problem? I was told before that it may be a resistor issue or related. Thanks for the help!