What kind of crazy car radio display is this?

[truereplica]

I picked up four identical used car radios.
They were made for the early 90's Taurus-
Sable. Since my dad has two wagons of that
vintage that both have bad switches, dead
displays, or both I thought I would give him
an early birthday present.

I tested all four radios. Sound was good, all
switches and pots were smooth with no popping
or static. However, there was a small problem.
The displays were dead in all four units!

I pried the top off one of the radio chassis
and immediately noticed a miniature version of
the kind of lamp sockets that are commomly used
for fender marker lenses, interior lighting,
etc. A small lamp housed in a half-round cover
attached to the back of the display was burned
out. By replacing this 25 cent lamp all four
displays would again light up.

The question I have is what kind of crazy,
looney, display am I looking at! From the
front bezel you see what appears to be common,
LED style, seven segment digits. All green in
color. Once I discovered that lamp behind the
display I grabbed my old copy of "Electronic
Display Devices" by Richard Perez. All of the
display types described in this very thorough
book generate their own light, except in the
case of black segmented LCDs that require back
lighting.

The display on these radios really do look like
old fashioned LEDs, but they can't be. If you
look closely at the display without the bulb
lighting it up the digits still function normally.
The segments are translucent so the light from
the lamp can filter through.

If the display is not LEDs, LCDs, VFDs, or ELDs,
what the heck is it? Did Ford create a new type
of display just for these cars?

[Enzo]

Why can't it be LCD? I am sure that is what it is. The color can be whatever color they want, the LCD is just a gate for the light. Consider the LCD based projection TVs. LCDs are not limited to black on gray.

In the pro audio stuff I work on, there are all manner of LCD displays on the sound processors. Most these days are back lit, either by LEDs or by EL panel. I dabble in consumer audio as well, and I see many receivers with LCD displays, some of which use a simple bulb behind them, just like your car radios.

[Externet]

Hi.
Sould be a transmissive-only green dye LCD, it needs conventional lightbulbs as backlighting.
Miguel

[Gorgon]

Hi,
I once bought a clock radio with a backlit LCD blueish display. In a short time the light went, and I opened the radio and found 4 small bulbs with a blue rubber cover. I replaced the old bulbs with 2(I didn't have more) white 3mm LEDs, put on the same rubber cover, and the radio has worked excellent for many years. So, using LEDs for replacement is a good idea, specially in cars, where the vibration can wear the bulbs.

TOK

[truereplica]

I guess the thing that really had me twisted in
knots was when these radios were designed and
manufactured. They were put in cars starting
around 1985. They didn't change at all over
the next several years.

These days, the brilliant colors found in LCD TVs
and monitors are commonplace. The lamp I found
behind the display looks like something out of
Edison's workshop!

Instead of thinking logically, my mind went back
too far. I should have realized that the kind
of primitive displays I was thinking about were
around in the early '70s. By the mid to late
'80s LCD technology was widely available in a
whole range of devices.

You guys are very right, and I was very wrong!

truereplica