Back Light Spreader for Casio F-91W, A-158, A-159, A-171, W-59, F-94W, Sensor, Ollee, and more. Drop-in, No Soldering Modification / Upgrade

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C.L.I.C.K........H.E.R.E........F.O.R.......M.O.R.E.......I.N.F.O
This light spreader replaces the original to create an even glow that makes the backlight more usable. The LED and circuitry of the watch is not modified; this mod simply uses modern optics to distribute the light better!
• NO SOLDERING - disassemble, place the components into the watch, and reassemble.
• No modification to the LCD films required! No handling or trimming of sticky fragile films.
• Sleeper mod: When the backlight is not being used, the watch looks stock.
• No reduction to the 7 year battery rating as with other LED replacement mods, dual-LED mods, or the a700 module swap. Cheaper than buying the a700 for a module swap.

Known fully compatible models:
• Module 593 (F91W, A158, A159, A171W, F84W, Sensor Watch, Ollee Watch, and more)
• Module 590 (W-59)
• Module 1071 (F94W)
• A159WGEA-1, F91WM-9A, F91WG-9 (These require the "V2 YDR" light spreader variant)

Each order includes 1 plastic light spreader and 1 piece of backing. The backing is essential to the function of the light spreader. You have a choice of 3 different variants of backings, described below. You can put a graphic on the backing and it will show up only when the backlight is on.

Light Spreader Variants:
• V2: The latest version of the light spreader. Does not work in oil filled / hydromod watches.
• Oil Compatible: This experimental version of the light spreader was intended to work in oil for hydromods, but due to poor performance, I am not making any more.
• V2 YDR: V2 with a Yellow Diffuse Reflector for use with the following watches: A159WGEA-1 (Shiny Gold Vintage A159), F91WM-9A (Painted matte gold F91W), or F91WG-9 (Black with gold trim+buttons F91W). These models MUST use the YDR version of the light spreader, and the YDR version will ONLY work on these models. You cannot use the V2 YDR with regular F91W's with their usual grey/silver LCD's. When installing, the yellow film must be facing front, touching the backside of the LCD glass. ESR backing is recommended for this light spreader for the most even light (least left to right gradient). Please be advised that the V2 Thin YDR combination is the least even looking light and has the most brightness gradient appearance from left to right.
• V2 Thin: This is a thin version of the light spreader intended to leave space for the Sensor Watch custom LCD, the Ollee Watch PCB, or the aliexpress positive STN LCD. You can also buy this to minimize the risk of LCD cracking, but the trade off is that the light is less even with some backings. ESR backing is highly recommended for this light spreader for the most even light (least left to right gradient). Please be advised that the YDR version of the V2 Thin has the least even brightness gradient out of all the light spreaders I make.
• No Light Spreader: you will get the backing only. Use this option if you want to order extra pieces of backing material. If you are a new customer and you ONLY order this, I will assume you made a mistake and I will automatically cancel your order, unless you send me a message first or leave a note in the personalization text box about it.

Backing Variants:
• Paper: Spreads light very well and evenly. Not compatible with oil.
• Lumed Green: A piece of luminous material that will allow you to read the watch in pitch dark for about 40 min without using the LED light. You can improve its performance by charging the luminous material with a bright flashlight or holding it next to a light bulb for 10 seconds. The effect is quite subtle and will not be visible if your eyes have not dark adapted. Install this in the place of the paper with the greener matte textured side facing front. It does not change the colour of the LCD.
• ESR Film: This non-conductive mirror film material will reflect 98% of light and looks overall about 10% brighter than paper backing. Peel the yellow/frosted protective films from both sides to expose the silver mirrored surface before installing. When used with V2, the light is not as diffuse as paper or lumed green backing, but can be brighter depending on your viewing angle. The mirror reflections will also create an illusion of depth as the hotspots of the light move depending on your viewing angle. Recommended for use with the V2 Thin because it effectively doubles the V2 Thin's thickness into a more optimal range for even lighting. Also recommended for V2 YDR. Will not interfere with a NFC tag.

Compatibility with other mods:
• Aliexpress STN LCD: Positive and transparent STN works with V2 Thin. The negative is too thick and does not work with any light spreader.
• Ollee Watch: V2 Thin fits perfectly. The NFC sticker must not be placed behind the LCD as Ollee's manufacturer recommends; it should be stuck to the inside of the watch case just above the clear window of the crystal, with 2 upper corners bent to follow the inside wall of the case.
• Sensor watch PCB Only: Works with V2 and any backing.
• Sensor watch PCB and custom LCD: Works with V2 Thin, V2 Thin YDR, and ESR backing.
• Hydromod: not compatible!
• Fake watches: Check the LCD and PCB carefully to identify counterfeit F91W's.

>>>>>>>>>>>THE LCD GLASS CAN BREAK<<<<<<<<<<<
The LCD glass is fragile, and can crack if the light spreader, the backing, or the zebra strip is not installed correctly. If the LCD cracks, it is not recoverable, and you must try again by buying another LCD. I install these light spreaders to make completed watches several times per month and have never cracked an LCD doing this, and dozens of people successfully install the light spreader each week. But cracking does happen for some customers and it’s always very upsetting when it happens. You must accept that this watch was never designed to be end-user serviced, and that by opening the watch, you are taking a risk that you could mishandle the parts and break it. I am nonetheless very interested in tracking down the causes of LCD cracks and working to reduce their occurrence.
Below are some reasons why the LCD will crack. This list is derived from reported cases of LCD cracking where the buyer and I were able to communicate and diagnose the cause, correct the installation technique, and confirm the correction was effective through a successful reattempt. This is not an exhaustive list, because some people do not reach out so I’m not aware, or do not respond to my messages to go through the diagnosis process.
• The watch was fake. On the genuine one, on the battery side of the PCB, there should be a grid of dark green squares/diamonds thieving pattern. Fakes do not have this pattern, and the fakes' white frame is not spacious enough to fit the light spreader.
• Zebra strip was left in the white movement frame, preventing the LCD from inserting fully. The zebra strip must be removed so the LCD glass can be inserted all the way, as far as possible toward the 12 o’clock direction.
• The protective film on the ESR backing was not removed, causing it to be too thick and not leaving enough space for the light spreader.
• The original stock light spreader was not removed.
• Customer cut their own backing which was too big to fit flush into the indent in the white frame.
• Customer mistook the taped white cardboard sleeve used to protect the backing during shipping to be the backing, and installed the whole thing into the movement and then tried to force the glass in.
• Light spreader was inserted in the wrong orientation. The prongs must face the 9 o’clock position and the rough side must face down towards the PCB. The prongs tuck into a slot in the white movement frame.
• The backing and light spreader jumped up out of their indent in the white frame due to static attraction as the LCD was inserted, pinching them. Customer did not stop, continued to force the glass in, leading to crack. As you lower the LCD, ensure that the light spreader and backing correctly settle into the inset groove in the white frame by shifting them around with your finger from below. The glass will flop down by gravity until it is almost flat. If it sits up at a more than 20 degree angle, something is wrong, so DO NOT FORCE THE GLASS DOWN, clear the obstruction first.
• The white frame’s latch at the 6 o'clock position was not pulled back to reinstall the LCD glass, and the customer forced it thinking it would be self-retracting like a door latch. This latch is not self-retracting, and MUST be pulled aside again before tucking the glass under it. You needed to pull this latch aside to release the LCD, and now it must be pulled aside to let the LCD back in again.

All of these causes have a theme of too many things sitting in the optical stack and causing it not to sit flat enough, and then the customer forced the glass despite the obstruction. So DO NOT FORCE THE GLASS, examine the installation carefully. The glass should be able to flop down mostly flat, resting at a 15-20 degree angle, before you can gently press it with just a few grams of force the rest of the way until it’s flat.

If your glass breaks, I WANT TO HEAR ABOUT IT! Message me so we can figure out what went wrong and how to avoid it in the future, both from your side with installation technique and from my side with product design and instruction. It’s only a total loss if you just give up or leave a review saying it broke without figuring out why, because there's nothing anyone can learn from it.


Installation instructions:
FULL VIDEO TUTORIAL: https://youtu.be/s5IYBeU6_m8
How to install the V2-YDR with ESR backing on a gold LCD module: https://youtu.be/T74yKkJk4rY

1) Disassemble the watch until the LCD assembly can be removed from the white module frame. Be careful handling the LCD since the plastic polarizer on the front is very soft and easily scratched, and never place the LCD face down on the tabletop. Ideally, work in a clean environment and wear nitrile gloves to avoid leaving skin grease on the parts. Do not touch the inside of the watch crystal and leave it face down so dust does not land on it, as it is very difficult to clean without damaging. Masking tape (painter's tape) rolls can be used to stick off dust motes and light grease marks.
2) Remove and DISCARD the original white plastic light spreader located behind the LCD. It is no longer needed.
3) Place the included rectangular backing into the module frame. Ensure that the cleanest side of the paper is facing outward, or the matte or greener side of the lumed backing is facing outward.
4) Place the new light spreader into the frame. Ensure that the pitted side is facing down towards the backing, away from the LCD. The notch of the light spreader will go where the LED goes, at 9 o'clock.
4b) Clean the light spreader front surface and back surface of the LCD to make sure no dust gets trapped here when you install the LCD glass.
================CAUTION ========================
This next step is where the LCD glass can break:
5) Reinstall the LCD glass assembly, making sure not to push the light spreader out of its groove in the frame. Using your fingernail, stretch the bottom latch of the LCD holder on the module frame away from and over the glass to hook the LCD securely. ***Do not force the LCD against the latch, it will not move aside on its own, and doing so will break the glass. *** You MUST pull it aside with your fingernail to let the LCD in and put it back carefully around the LCD. There will be some tension as the new light spreader and backing is slightly thicker than the original. Ensure that the light spreader does not shift towards 12 o'clock during installation and block the gap for the zebra strip, or else you can crack your LCD glass if it pinches the light spreader.
6) Inspect the LCD from the front. If there appear to be bumps in your LCD screen, this means dust was trapped between the LCD and the light spreader. Cleaning out the dust particles (e.g. sticking them off with masking tape) will remove these bumps. You will have to remove the LCD and reinstall it after cleaning. The dust particles may stick to the front of the light spreader or the back of the LCD, so don't forget to clean both sides.
7) Reinstall the zebra strip, the electronics board, and the metal back clip. Perform an AC RESET by electrically connecting the gold contact point at 1 o'clock position above the LCD to the metal back clip. Take your time to inspect and clean each part while reinstalling. If any segments are missing, it is likely due to dust contamination on the zebra strip. Stick any dust off with masking tape. Ensure the pushers are seated correctly, clean and reinstall the gasket, then finally the backplate and screws. Take care not to overtighten and strip the screws.

Message me if you need help!

I first created these light spreaders in 2023 and I ONLY sell them here on my Etsy store. I do not sell on ebay or on any standalone shopify websites. As a major marketplace platform, Etsy offers the best shipping insurance, buyer-friendly policies in case of disputes, and buyer review system - beware that other websites will not offer such buyer protections, and can host manipulated reviews.

If you are combining mods or creating something entirely new in a way that differs from what my installation instructions covers, message me to ask about compatibility!

Completed watches are available: A brand new genuine watch can be modded by my experienced hand and shipped to you! See my other listing: https://www.etsy.com/listing/1621733841/prebuilt-modified-casio-f-91w-with