Kenwood TS-140S Meter Backlight Replacement

Discussion in 'Radio Circuits, Repair & Performance' started by KA2IRQ, Oct 11, 2019.

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  1. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    I have a Kenwood TS-140S that after 31 years, finally blew out the backlight for the meter.

    The service manual says the rating on the bulb is 14V @ 80mA - anyone know an equivalent bulb and how it mounts? I wouldn't mind replacing it with an LED/resistor combo if it isn't too bright and can be made to fit correctly.

    I've never had the front panel of this radio off, so I have no idea how difficult it is to replace the bulb. The service manual doesn't really touch on it and I think only has one line drawing of the front panel removal.

    She's a good little radio- deserves some TLC.
  2. G4COE

    G4COE Ham Member QRZ Page

    I'd be looking at super bright white LEDs, less heat and more reliable..... a 'warm white' gives that incandescent bulb glow while 'white' gives that white clean glow, you'll need to use a dropper resistor because of the lower voltage, the current of them being around 25 to 30mA.

    For meters I use SMD leds and made a PCB strip to mount in meters that hold 2 or three SMDs, I got that idea when I put metere lamps in my linear Daiwa psu.

    If I get shadowing I either use a frosted strip over the top or take the gloss off the LED with a file or sandpaper. The frosted strip is the actual filters that comes from inside of defunct 'flat panel' screens..... never clod em out, cos there's usually a good thick sheet of plastic in there that could be put to many usage..... and bags of Mylar sheets.

    If you got the manual have a look at the explosion diagram that's shows how all the parts are put together. Quite a long time I did a TS140, think you'll find it pretty easy, some sets you just undo a couple of screw's leaving the bottom one in that hold the front panel allowing it to tilt forward.

    K9ASE likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    This place seems to have the original lamp. As I recall, once you disassemble the panel and expose the subchassis, the lamp just "plugs in" to the rear of the meter (I think -- it's been several years).
    TS-140 meter lamp.PNG

    If they or anyplace else doesn't have it, you could certainly use an ordinary 30mA LED that fits, in series with a 270-330 Ohm resistor; if that's too bright, reduce current by going to a 470-560 Ohm resistor.
    KA2IRQ likes this.
  4. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    Cool! Thank you for the info. That place didn't come up in any of my searches (or I just missed it).

    Yes, I watched a few repair videos on the radio, seems pretty straightforward. I believe you have to swing open the inner chassis and the bulb is right there.
  5. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    Yeah, that "Discont" in QTY means they have nothing in stock. I did find the replacement bulb on eBay however, so I get to keep it "original."
  6. G4COE

    G4COE Ham Member QRZ Page

    I can't recall if I used 5mm or 3mm LEDs...... well worth giving it a try, some rigs used coloured sleeve over the bulb should you use an LED this sleeve can be removed.

    The LEDs can be connected in series with one common resistor or connected in parallel with each having a resistor, you'll need to drop LED Voltage (typically 2.5 to 3V per LED) minus the bulb voltage (12V) aiming for 25-30mA of current... no need saying they don't 'pop' like bulbs. Standard LED types can be a bit dismal compared to super-bright.

  7. KA5IPF

    KA5IPF Ham Member QRZ Page

    Go to your local hobby shop and buy the appropriate bulb. They are used in trains.
    KA2IRQ likes this.
  8. W9GB

    W9GB Ham Member QRZ Page

    You have a LOCAL Model Train Store, in your backyard (Eatontown)
    They have used 14 and 12 Volt miniature bulbs (“Grain of Wheat”, T-1 size) since 1950s.

    The Traindoctor
    1301 West Park Ave

    Hobby Shop
    (732) 660-7062

    Jersey Shore Hobby Center
    2175 State Route 35
    Hobby Shop, Art Supplies
    (732) 449-2383
    OTHER Area Retail Stores:

    HobbyMasters in Red Bank.
    The Hobby Shop in Matawan
    East Coast Train Parts in Manalapan
  9. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    I didn't realize those bulbs were used in hobby stuff like trains or I would have gone that route... already ordered the bulb.. but thanks.

    I'm not sure the Traindoctor is still open- if it is the store I think it is, it was closed years ago. Hobby Masters is run by Tom, N2VFK, old buddy of mine- great guy.
  10. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    Different store.

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