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Heathkit Question

Discussion in 'Electronic Repair' started by Ralph Farr, Nov 3, 2003.

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  1. Ralph Farr

    Ralph Farr Guest

    Hi all,
    I have a quick question I was wondering if someone might be able to
    answer. What is the standard light bulb number for the 5V lamps in a
    Heathkit GC-1195/1197 clock. They are 5V miniature wedge type light
    bulbs that are used for the display segments. I guess this could be a
    proprietary Heathkit part, but I was hoping maybe someone had changed
    these and maybe knew if there was a standard bulb equivalent (the
    Heathkit part number is 412-621. Thanks and I do appreciate any help.

    Ralph Farr
     
  2. Jerry G.

    Jerry G. Guest

    What you should do is see if you can get a Newark or equivalent catalogue
    and carefully go through it. There are hundreds of different types of these
    small lamps. I am sure that your lamps are of some standard. I doubt very
    much that Heath had their own made, especially in the time that they were
    around.

    If there are any electronic suppliers in your area, which you can check to
    verify in your yellow pages, pay them a visit with a sample of a lamp. You
    can try Radio Shack, or a TV service place, but these would be very limited.

    If you know the voltage and current rating of the lamp, you can probably
    substitute it and also install new sockets to match. This is too much of a
    hassle for something that is standard.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    Hi all,
    I have a quick question I was wondering if someone might be able to
    answer. What is the standard light bulb number for the 5V lamps in a
    Heathkit GC-1195/1197 clock. They are 5V miniature wedge type light
    bulbs that are used for the display segments. I guess this could be a
    proprietary Heathkit part, but I was hoping maybe someone had changed
    these and maybe knew if there was a standard bulb equivalent (the
    Heathkit part number is 412-621. Thanks and I do appreciate any help.

    Ralph Farr
     
  3. Neil

    Neil Guest

    They sound like a standard wedge base 5v lamp. Can you scan or photo this,
    and I will match.
    Kim
     
  4. Jim shedden

    Jim shedden Guest

    Hi Ralf,

    I built one of those clocks a long time ago and it is currently
    lounging on my "to play with" pile. It was a great conversation piece,
    and always drew comments.

    Those little bulbs are problematic. I've had the clock for years and
    they get loose in the socket, or burn out at different times. I'm
    planning on replacing them with high brightness L.E.D.'s. You could
    measure the lamp voltage with the photocell light (I think I remember
    the intensity increasing with room light) and calculate an appropriate
    value of series resistance for the LED. Glue it into the segment,
    wire it to the board with soldered connections and you are done for
    probably a few decades. I did illuminate a segment red, and it looked
    great (keep the LED at the back of the bulb hole so the segment can
    spread the light). I'd love to see it in blue, but then you get pretty
    expensive.

    Illuminate a segment for yourself with a LED before you commit to
    hacking it up. If you use multiple LEDs per segment, I'm sure you can
    make the thing overly bright.

    As I said, it is waiting for me to try and I have no final report. For
    me, if it doesn't work out, I'll trash the clock anyway. I'm done
    playing bulb-boy.

    That clock used to throw off some warmth from the linear regulator.
    This should save some power as well.

    Now, if you could only add the "atomic clock" circuit so the thing
    sets its own time on power outage...

    Good Luck,

    Jim
     
  5. Ralph Farr

    Ralph Farr Guest

    Thanks for your reply Jim - I had never thought about using LED's but
    that is something I would definitely consider now.

    Ralph
     
  6. James Sweet

    James Sweet Guest

    Seems it would kinda lose some of it's vintage charm if you did that,
    incandescent segments are something you don't see much these days.
     
  7. Bob M.

    Bob M. Guest

    Yeah, and the reason you don't SEE many of them any more is that they keep
    burning out!

    Perhaps the way to keep the vintage stuff original would be to put a small
    value resistor in series with the bulbs so they last longer. They'd be
    dimmer, but put it on a shelf near the ceiling where it's darker anyway and
    maybe no one will notice.

    Bob M.
    ======
     
  8. James Sweet

    James Sweet Guest

    Well yeah, I didn't say incandecent was very practical, but it's cool none
    the less. Someone else mentioned this unit has a photocell to dim it when
    the room is dark, one could probably just put a variable resistor across or
    in series with this to adjust the max brightness, dimming it 20% would
    extend lamp life considerably, but then if you get a large quantity of
    replacement lamps it'd be pretty easy to just replace them when they burn
    out, or group relamp the segments that see the most use.
     
  9. Hi

    You can go a long way to drive the life of the bulb up with two
    resistors. Put one resistor in series with the bulb to knock down the
    applied voltage. The other resistor is put in parallel across the switch
    to put just a little current through the filament when it is supposed to
    be off. It should just glow faint red. By doing this, the inrush current
    is reduced since the filament is already hot. Inrush current is what
    kills the bulbs.

    Regards
     
  10. Jim shedden

    Jim shedden Guest

    Sorry on the mis-type of your name.

    The control chip is, apparently, National MM5387AA/N

    Can't vouch for the source, but here you go:
    http://www.chipdocs.com/pndecoder/datasheets/NSC/MM5387AAN.html

    Jim
     
  11. Jim shedden

    Jim shedden Guest

    Sorry on the mis-type of your name.

    The control chip is, apparently, National MM5387AA/N

    Can't vouch for the source, but here you go:
    http://www.chipdocs.com/pndecoder/datasheets/NSC/MM5387AAN.html

    Jim
     
  12. I did something like this once...

    I'd been playing around with LM3915 bargraph display chips, and after getting
    some LEDs going, I wanted to use incandescent bulbs. So I built a driver
    board, and across each switching transistor I put a 100 ohm resistor. When
    the power was on you could just *barely* see the filament glowing. Never had
    a bulb burn out, either. (These were #47 bulbs, for whatever that's
    worth.)
     
  13. Ralph Farr

    Ralph Farr Guest

    Thanks everyone for the replies - it has been a very interesting
    discussion. I do like the vintage light bulb segments, but it would be
    great to improve reliability. I was thinking about possibly using clear
    white LED's to replace the bulbs. I haven't worked with any white light
    emitting LED's - are there any as bright as a miniature incandescentt
    lamp or would it take several to equal the same brightness?
     
  14. Jim shedden

    Jim shedden Guest

    Hi James,

    I read the Heathkit circuit description and it basically says the full
    lamp voltage is 5 volts regulated and will dim from there. So if you
    want to keep it vintage, I would look into Chicago Miniature lamp #86
    available from 'www.mouser.com' as p/n 606-CM86, they are T1-3/4 wedge
    base at 6.3 volts rated 20,000 hrs.

    That seems to indicate that they will last over 2 years. In my
    experience, whenever anyone commented on the clock and I said I had
    built it, the next minute the time was in Klingon (When all were
    looking, of course).

    The sockets seem to be problematic as well, many times I opened it to
    relamp, and it was just the way the segment was pushing on the bulb.
    In my opinion it is a poor and frustrating design.

    Sorry I didn't post the p/n right away, but I actually had to open the
    clock and measure the bulb. I'm lousy at judging dimensions.

    LED's, that's for me!

    This thread is going to make me break out the soldering iron. I have a
    few "white" led's that could be tried. I guess if you get the vintage
    color that you like the only difference would be that the LEDs may
    turn on and off more abruptly. You could probably ramp the voltage on
    the flashing colon to make this unnoticeable.

    For some real fun put an RGB tri-color LED and drive circuit in. You
    could probaly match the color of the lamps then. See

    http://www.superbrightleds.com/TriColor LED.htm

    You could program it to randomly change colors every 5 minutes. Now
    that would be a conversation piece! It would look great right next to
    the lava lamp. Burn some incense, put on your John McLaughlin albums
    (you know, the big black CD's). Let people worry about your sanity,
    maybe a vacation will be suggested!

    Regards,
    Jim
     
  15. Ralph Farr

    Ralph Farr Guest

    Thanks Jim for actually opening up the clock and checking out the bulb
    for me - I didn't mean for you to go to that much trouble! I really do
    appreciate it though. Are these the ratings for the original heathkit
    lamps - 6.3V .2A or is the original no longer produced? I was just
    wondering since the clock outputs 5V to the bulbs - I guess that was to
    dim the output a little and possible prolong bulb life. Thanks again for
    your help.

    Ralph
     
  16. James Sweet

    James Sweet Guest

    They're quiet bright, but generally in a rather tight beam, also they have a
    much higher color temperature, they look more like fluorescent light.
     
  17. verni

    verni

    3
    0
    Apr 4, 2007
    lamps

    I have same clock grandfather type still going strong since mid 1970's.
    the lamps that i use are from arcade machines i got from company in england same type wedge 6v..any wedge 6v will always do if same size..mine works perfect..have photo of clock still running with them in it if u want i can email u it.
    my email address is ......regards vernon...p.s like the remark junior member..lol i'd show em how to build things..lol
     
    Last edited: Apr 4, 2007
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