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Hi All,
1st time here in the forum … had lots of trouble getting in here for some reason.
I have this old vintage keyboard made by Emu systems … it’s a Proteus MSD or MDS. I found the LCD display backlight is shot. So took it apart to get at the backlight and found these LED’s that recognized right away as I had bought a few years ago at a local Chinese owned electronics shop in Vancouver BC … Lee’s Electronics. I called them up and they no longer carry it and the manager couldn’t even say what it was or where they sourced from … no doubt it was China but I have SCOURED the net and found ONLY 1 image of one from a company in the UK. I emailed them to see if they could identify it and they have not replied. I just realized it looks like I cannot post an image of it here.
Guess U can post images so here it is …
Basically I need to know a series number etc or a package ID … what did they call this package ?
Or anyone know who manufactured it in Asia somewhere … If I can’t find a replacement … I figured out a McGuiver to rebuild it but I’m even having trouble sourcing a 1608 or 1205 package that will be bright enough and with the right dimensions to fit into the old slot this one came out of.
Any help much appreciated …
Journey
Quick addendum about the McGuiver fix … I plan on soldering at least 3 small smd (1608 or 1204 pkg) or something close to 3mm x 2mm x 1mm … chain them together and then attach leads to attach thru hole to the display board. Having trouble finding anything at digikey that has any brightness above 250mcd with the right dims.
The McGuiver fix is to solder 2 or 3 LED’s in a chain to fit into the slot for this beast and attach thruhole leads on each end to connect to power. Problem is finding a small pkg that has enough mcd times 6 to light it up enough. 3 LED’s on each side in a chain so lets say 6 times 240mcd … not sure that’s gonna cut it it for backlight. Thinking a guy needs at least 5000 mcd from both sides for a decent backlight ?
It’s 16x2 lcd dislpay … so total length of backlight panel is about 65mm.
I looked into getting a new display … unfortunately the new ones don’t have the same pinouts in the right positions and no schematic to just run jumpers … the new displays have labeled pins but the old one doesn’t and no schematic. I suppose I could get new display and just and just remove the backlight and transfer to original display ? If this is possible then those LED packages are STILL available somewhere ? Don’t really care what color it ends up being … original was yellow. I think the original LED was white with a yellow lens.
In equipment from last century it would have been extremely unusual to have anything but red, orange, yellow, and green LED colors. Blue, and White (via phosphor) were outrageously expensive even in the late 1990s. So I’d bet it is a standard yellow LED which have been available and relatively inexpensive since the early 1980’s.
As to the mcd rating needed it is not always easy to figure out. I remember backlight systems from last century that used surprisingly low mcd devices but do to the electrical drive characteristics and optical design seemed 100X brighter than expected based on the mcd rating alone.
I’d buy some bright yellow LED’s and try them out. Here’s a search result of 43 flat top yellow LEDs in 0603 (1608) and > 100mcd (they go up to 430). https://www.digikey.com/short/wv79hjpf
Hi Paul,
Thanks for your response …
If my memory serves me right … when I bought a few of these LED’s say back in around 06 maybe a bit later … they were quite bright and I believe they were just plain white.
The LED’s in this particular back light look like they have a yellow lens so the actual LED should be white.
I did a search on when this keyboard was released but didn’t really find this particular model but I’m gonna guess mid 90’s to late 90’s … so these LED’s aren’t that old school.
I guess you have no idea about this particular package design ?
I am posting a pic of the plastic piece that the LED’s were mounted in … and the McGuiver fix I was planning. The McGuiver is only two of 3 chained smd LED’s I scavenged from a junk pcb but you get the idea … a 1608 metric fits just perfectly in the slot where the longer originals fit into the slots. The originals are side view LED’s and project their light across the plastic with a very white piece of plastic to illuminate. Does’nt really matter what color the back light is but I’m thinking blue or white would be acceptable because they might be available in a higher mcd rating. So with 3 chained together on each side a low mcd rating might be just enough. The other odd thing I saw was the current limiting resistor for both original LED’s was only 15 ohms. So I’m expecting to have to increase this value for the McGuivered solution.
On the McGuiver fix pic you can see how I am chaining them together … I had issues with these old scavenged LED’s … but I did manage to get 3 chained and installed into the plastic form but found they were no where near bright enough but the concept will work with the right LED’s … diffused lenses and very dim as far as mcd rating goes. Interesting how you were able to find at digikey all these possibilities. I have been using the filters to search and keep coming up very short On my last attempt I did find a white LED at the right dims and around 240 mcd … so I’m hoping 6 of them will do the job. I guess it would be nice to keep the original back light color to keep it original. Maybe worth a bit more money in original condition. I’m actually considering buying this board but for now it will probably be put up for auction on Ebay.
I’m taking a guess here but pretty sure the voltage supply for the back light is 5vdc which would explain why the current limiter is only 15 ohms. Another McGuiver I was considering was using say 3mm round LED’s only if I can fit them in the space available but would still be a daunting task as the room is very limited … clearances are quite tight. Actually rectangulars would be a lot better but just cannot find them on Digikey, everytime I search I get zero stock. I will go over the link you sent and see what I can find … on a quick glance at it I saw many that would probably be too dim … but maybe I’ll get lucky ?
Just saw a 0603 smd unit at 430 mcd which is a lot smaller than what I originally was looking at and I could probably chain 4 of them together for each side and they should fit nicely into that slot.
Damn yer good with your searches on Digikey … most times I search for something I get mostly NON stock items … what is your secret ?
Here’s where I found a pic of what I am search for but they have not responded to my email https://www.plusopto.co.uk/ledcomponents.html
Look at the thruhole image and you will see that LED there …
Weird ass thing is that there is no catalog link for the thruhole stuff.
So the pkg I found at 430mcd times 6 or maybe 8 would be 2580 or at 8 would be 3440 mcd …
Actually this pkg would be kinda a sloppy fit but suppose I could glue it once installed …
The package in the McGuiver pic measured 3mm x 2mm x ~1mm which I think is a 1608 metric
I’m gonna try it and see … I’m a good enough McGuiverer to make it work …
Actually looking like I can chain 5 of these per side … after looking at the viewing angle for this unit …
maybe 3 or 4 should do the trick ? 140 degrees … to remind the plastic lens for the back light is 69 mm x 20 mm x 1.9 mm
