Old lcd display  - Page 1
Forum section: electronics / repair

author: Bjarni Raf
author_rank: Newbie
timestamp: July 20, 2018, 10:05:46 pm
content: Hello everyone, i got this sampler akai mpc3000 with an dead backlight on the display , And what i want to do is to change that display for a new one with a led backlight. I did this with another sampler akai S950 to be exact. But that one had different display 2x40 i bought one from buydisplay.com it had 16 pinout compared to 14 on the older one, main thing i was able to bypass the inverter and use that to light the led backlight.On this new mission that I am on i can’t seem to find a lcd display 240x64 without a micro controller, cause the micro controller chip is mountent on the cpu board on the sampler. The chip name is Sanyo LC7981 5h2.I was wondering if it is somehow possible to bypass the micro controller on the new lcd screen or reversed that is to bybass the micro controller on the cpu board?Ive attached some pictures aswell.1st is from the service manual of the akai mpc 3000, pinouts from the display to the cpu board2nd is the sanyo cip pinout,3rd is from the pinout of a new lcd display,4th is pinout of the micro controller of the that newer lcd display.I am noexpert at electronics so i excuse if my queations are dumb.Hopefully some can point me in the right direction

author: ArthurDent
author_rank: Super Contributor
timestamp: July 21, 2018, 12:03:04 am
content: It looks like the backlight in your display is an EL panel and you may be able to just buy another one on Ebay for about $10 and use the existing display which could be a lot simplier. I had a signal generator that had one that grew so weak that I had trouble even telling if it was on in a darkened room. I bought another panel that was a little bigger and cut it to fit. The unit already had a supply for an EL panel so I used that instead of the one included with the new panel and it worked great. They come in different colors so you should be able to find a color that is close to the original.https://www.ebay.com/sch/i.html?_nkw=electroluminescent+panel

author: Bjarni Raf
author_rank: Newbie
timestamp: July 21, 2018, 09:09:32 am
content: Hey ArthurDent, I didn’t know about these ones, but i know that i can order the “original” el backlight on ebay from couple of sellers,I just wanted to find out a way for it with a new lcd with led backlights cause it looks much better on my other sampler compared to the old with an el backlight, plus i think the led backlight would last longer,I also fitted a led strip to try to make my own led backlight but it was way to strong , I saw each dot of the led lights shining through the lcd screen, it would work if i would find some material to diffuse the lights on the led strip under the display itself, or if i could find a led backlight on the web, but i just thought it could be easier with buying a new lcd with led backlight cause they are not expensive and easily found

author: james_s
author_rank: Super Contributor
timestamp: July 22, 2018, 05:52:42 pm
content: I replaced the EL backlight on one of my scanners with a new EL strip from ebay. I couldn't find one the right size so I trimmed it with scissors to fit. It worked fine, that was several years ago and it still works.

author: ArthurDent
author_rank: Super Contributor
timestamp: July 22, 2018, 05:59:04 pm
content: If you really want to go with an LED backlight you might be able to adapt the method described in this thread about putting an LED backlight behind an LCD display that had no backlight. If there is enough space behind your display you could just slide the EL panel out and slide the LED backlight assembly in place. You can skip the steps about disassembling the display and removing the reflective backing strip because your LCD doesn't have one. It might be worth trying.https://www.eevblog.com/forum/projects/hp-3457a-lcd-backlight-mod-(also-for-3478a)/

author: Bjarni Raf
author_rank: Newbie
timestamp: July 23, 2018, 03:17:56 pm
content: Those led backlights strip looks nice, think im going for that one! Thanks guysBut there is already a inverter drivining the el backlight on my screen, would i be able to remove that inverter and use that one that comes with the led backlights on ebay?Its the output called el out on the drawing in the attachment

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 04:52:45 pm
content: Yes, or just desolder one end of R851 and pop it out of the hole, that will disconnect power to the inverter while leaving it intact so someone else can hook it back up if they wish.

author: Bjarni Raf
author_rank: Newbie
timestamp: July 23, 2018, 05:24:51 pm
content: But where will the inverter for the led backlight go? Or is the inverter not necessary?

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2018, 06:04:29 pm
content: LED backlights don't need an inverter. Some may require a boost converter but that can be tapped into the same 5V source that previously powered the EL inverter.

author: Bjarni Raf
author_rank: Newbie
timestamp: July 23, 2018, 07:38:16 pm
content: Nice thats handy! Thanks for the help