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803Re: [Altair Computer Club] Re: LED Mod for front panel on my Altair 680

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  • Dan
    Sep 3, 2005
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      Yep, thats the one. I've been reading over the assembly manual since I
      dug it out. It's weird seeing how I begin to remember building this so
      far back. I noticed that I actually have a 680b from references within
      the documentation. Although I recall the front panel silkscreen never
      said 680b. I saw online that the 680b was the big seller by MITS and the
      first version was somehow discontinued. I'm getting mine all
      dissassembled now to check all the connections and clean it up a bit. I
      have to check the power supply still and hope it's still alive.

      =Dan

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      Tom Sanderson wrote:

      > You could solder in socket pins and change or replace LEDs a will.
      >
      > Here are some pictures of the 680 front panel:
      >
      >
      > http://www.virtualaltair.com/systems/680/images/680FP3W.jpg
      > http://www.virtualaltair.com/systems/680/images/680FP5W.jpg
      > http://www.virtualaltair.com/systems/680/images/680FP6W.jpg
      >
      > Tom
      > --- In altaircomputerclub@yahoogroups.com, Dan <ragooman@c...> wrote:
      > > Hi,
      > >
      > > I would guess looking at a couple dozen hi-brite LEDs would get
      > blinding
      > > after a few seconds. The red hi-brite LEDs I have can run up to
      > 2.5v and
      > > 30ma and have about 7000mcd of light. I think I'll just keep the
      > regular
      > > LEDs in there now. Thanks for the info on your experience, I guess
      > the
      > > hi-brites are good only in some appl's.
      > >
      > > =Dan
      > >
      > >
      > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      > ~~~~~~~~
      > > [My Corner of Cyberspace
      > http://ragooman.home.comcast.net/%5d <http://ragooman.home.comcast.net/%5D>
      > > [Pittsburgh Robotics Society
      > http://www.pghrobotics.org/%5d <http://www.pghrobotics.org/%5D>
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      > http://groups.yahoo.com/group/pghvintagecomp/%5d
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      > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      > ~~~~~~~~
      > >
      > >
      > >
      > > Steve wrote:
      > >
      > > > Most 5MM LEDs, like those in the Altairs, are nominally rated at
      > 20mA
      > > > current consumption, but can usually be pushed to at least 30.
      > All
      > > > red LEDs have about the same voltage drop across them (about
      > 1.7V).
      > > > Whether "regular" or super-bright, those are the specs.
      > Therefore,
      > > > you could directly replace the original LEDs with bright ones,
      > and no
      > > > other changes would be necessary. Essentially, "super-bright"
      > simply
      > > > means more efficient- you get more light out with the same power
      > in.
      > > > Super-brights don't require increased voltage (or current).
      > It's the
      > > > COLOR that determines the voltage of the LED. The shorter the
      > > > wavelength, the higher the voltage drop across the device.
      > Infrared
      > > > runs at the lowest voltage, red is higher, then green, blue,
      > white,
      > > > and ultraviolet (White LEDs are really deep blue with a
      > fluorescent
      > > > white phosphor*). UV runs at about 3.5V. All consume ~20 to 30mA
      > > > nominally.
      > > >
      > > > I would recommend against using high brightness LEDs in your 680
      > for
      > > > 3 reasons:
      > > > 1) I had the same idea that you did- that brighter would look
      > > > better. I was wrong. The LEDs were bright enough to make it
      > very
      > > > difficult to read the writing on the front panel, and in an
      > indoor
      > > > environment, they were just too distracting. They might be OK
      > from
      > > > across the room, but up close they just don't work.
      > > >
      > > > 2) Using LEDs with clear envelopes rather than the difused
      > > > translucent "dull finish" type would look bad when the computer
      > is
      > > > turned off.
      > > >
      > > > 3) If you ever decide to sell your 680, those non-standard lights
      > > > will surely hurt the price.
      > > >
      > > > In the 8800b, each LED is powered by the unregulated +8V supply
      > > > through a 220 ohm resistor and a buffer. This means that they're
      > > > actually quite a bit overpowered at over 30mA each. The other
      > > > Altairs probably are similar. Superbright lights would be
      > blinding
      > > > at that level.
      > > >
      > > > But if you really want to jazz up the look, why not install
      > different
      > > > colors for the various functions? A rainbow of colors is
      > available,
      > > > and it's possible that you wouldn't have to change too many
      > resistors.
      > > >
      > > > steve
      > > >
      > > > * You can now find quite a few white LED flashlights on ebay that
      > > > only use a single 1.5 Volt cell for power. This would seem to
      > > > disprove my statement that more than 3V is needed to operate the
      > > > device. Not true. Those flashlights have inverters inside that
      > step
      > > > up the voltage to the appropriate level. I have a little 12-
      > > > LED/single cell flashlight here that actually works all the way
      > down
      > > > to a battery voltage of 0.2V.
      > > >
      > > > ==========================
      > > >
      > > > --- In altaircomputerclub@yahoogroups.com, Dan <ragooman@c...>
      > wrote:
      > > > > Hi,
      > > > >
      > > > > While I was working on my 680, I thought of something to do
      > with
      > > > the
      > > > > front panel. Seeing how the LED's on here were 30yrs old, (I
      > can
      > > > still
      > > > > remember soldering these on__uuggh__), I figured it would look
      > > > better if
      > > > > I replaced them with Hi-Brite LED's. Although these require a
      > > > little
      > > > > more voltage to attain the ultra-brite output, I would think
      > using
      > > > them
      > > > > still at the same voltage as the ordinary LED's would make them
      > > > stand
      > > > > out more and replace the somewhat dull finish look associated
      > with
      > > > the
      > > > > old style LED's. I had some lying around so I was going to try
      > a
      > > > couple
      > > > > to see how much difference there is. Has anyone done this yet
      > and
      > > > > experience any results ?
      > > > >
      > > > > =Dan
      > > > >
      > > >
      > > >
      > > >
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