[Elecraft] two translucent K2 LCDs still left (for sale) for your backlighting experiments

Thu Aug 7 14:57:00 2003

FYI I still have two left. $11.37 shipped in the US, foreign
shipping at cost...

These do NOT include any sort of backlight - you'll have
to make your own, but these translucent LCDs are perfect
for the task. Add two bright white LEDs, a 1.2K dropping
resistor, and some white material under the LCD and you're
set. My experiment results are below.

Andy

-----Original Message-----
From: Wallace, Andy=20
Sent: Monday, July 28, 2003 7:21 AM
To: Elecraft
Subject: [Elecraft] transreflective K1 LCDs for sale / backlighting
experiment results

Hi, folks!

Some of you may remember that I posted some info about
a replacement for the K1 LCD that is made for backlighting.

The current LCD is a Varitronix VI-321-DP-RC-S-12.
This is reflective, meaning it is made for front-lighting.

The company makes an identical function part, the VI-321-DP-FC-S-12,
which is transreflective - it can be lit from either side.

I later discovered that Lumitex makes fiber-optic-weave backlight
panels for LCDs:

http://www.lumitex.com/lcd_backlighting.html

I managed to get a couple of those, and went ahead and special-ordered
the Varitronix transreflective LCDs from Digikey. It looked
like this scheme would work, but it would require removing the stock
K1 LCD and substituting the other one, and finding a place to
put the Lumitex backlight, including the fiber bundle and the
LED holder, and picking up +12V off the front panel connector (where
I got power for the two lighting LEDs I had previously installed).

I made the swap yesterday. It was a tricky process. The old LCD had
to be clipped out, to avoid damaging nearby components with a =
desoldering
station. I then pulled out the clipped pins, one by one, removed the=20
old LCD panel (which is stuck VERY securely to the rubber spacer), and
clean out the LCD holes.=20

The new LCD is electrically and mechanically identical except for the
backing. Once you remove a protective sheet from the front and back
surfaces, the back has just a white panel attached. (In fact, this seems
to be the only difference between the LCDs - the stock Elecraft one
has a mirrored backing "sticker" in place of the white one. I tried=20
scraping off a corner of the mirrored sticker with my fingernail and
that stuff is held on VERY securely.)

Mounting the new LCD without the spacer simply involved placing the LCD
in the proper direction (same as the old one) and inserting the pins
through the holes so they JUST show at the level of the underside of
the board. I soldered four corners and made sure the alignment was
straight, and soldered the rest. I powered on and made sure the rig
still functioned normally.

The Lumitex backlight panel was too large for this LCD, but the company
told me I could trim it. The fibers are plastic so an ordinary scissors
worked fine. I trimmed it and trimmed off the unused fibers from the
bundle. It slid under the new LCD with some encouragement, and I wired
some temporary power for it. Lumitex recommended a 300 ohm dropping
resistor for 12V power sources, so I found a close value (330 ohms).

(My homebrew lighting scheme - common among K1 owners - was a pair
of high brightness white LEDs from Radio Shack, and a 1.2K dropping
resistor for about 5 mA current. That was bright enough. The Lumitex
fiber is a couple of inches long and that is one reason why pushing 20=20
mA may help visibility. As I never plan to use the K1 with batteries
that wasn't an issue.)

The Lumitex panel seemed to light the LCD very well. Illumination is
fairly even, though when the light hits the far end of the fibers, it
reflects back, so one edge of the panel is SLIGHTLY brighter than the
other. The white LED lights a little bluish (same as the Radio Shack
ones) but is a nice effect. Since the LED is in a normal snap-in
holder, I may experiment with other colors sometime.

I managed to route the fiber bundle out the left side of
the LCD and around the MENU pushbutton and then 180 degrees
back toward the right side of the front panel board, where I
routed power wires to the front panel connector (pins 20 and 16,
with the dropping resistor being a little SMD unit attached to
the pad at pin 16). I'll try to take some JPGs of it this week.

I was surprised that things fit fine (including the LED holder)
between the front panel board and the sheetmetal. I added some
electrical tape to the bottom of the LED holder for insulation
and to keep light from shining toward the right side of the=20
rig. Some light does escape the fibers on their way to the=20
backlight, though, so the panel buttons have a halo...

So anyway, I call it a success. The 330 ohm resistor lights
the panel rather brightly - I will probably increase the value
somewhat. As I said, current draw wasn't an issue, but I've
always thought a backlight for the K1 LCD would be a nice thing
to have, and done properly. This system seems to work well.=20

One idea to get around the continuous current draw
would be to parallel it with perhaps the RIT LED. That way, you
only run the backlight when you want to, and you can center the
RIT pot if you don't want RIT on. (Yes, XIT would turn off
the backlight!)

Now, I don't have another Lumitex panel, but this transreflective
LCD is very suitable for other homebrew methods of backlighting.
I tried a piece of white paper behind it with my original homebrew
LEDs, and it lit up fine, and you don't have to edge-light it
like the original LCD. It opens up other possibilities. A piece
of translucent white plastic might work super - edgelit with some
bright LEDs.=20

So with that in mind - I had to special order the LCDs and got
ten of them. I have nine remaining, and if List members would like
some, I'll sell them at my cost ($9.25 each) plus you pay shipping.
I need to see how I can pack these safely, and how much that would
be, but hopefully materials/postage won't be >$3.=20

The caveats:
1) you need to do this yourself, probably voiding your K1 warranty
2) you need to figure out your own backlight scheme
3) you will need to remove the old LCD, probably destroying it
4) you will need to clean the PCB holes out and install the new LCD
in the correct orientation, without the rubber spacer, and with
the correct mounting height, without damaging the front panel board
5) this is NOT "Elecraft approved" and therefore entirely at your risk!

If you accept all those terms I'd be happy to sell you the LCD!
Email direct, please.

Andy

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