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Amp Supply LK-500-NTC Variable Capcitors

Discussion in 'Amateur Radio Amplifiers' started by K1SR, Dec 20, 2016.

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  1. K1SR

    K1SR Ham Member QRZ Page

    First of all hope everyone is having a good holiday.

    I'm trying to find two variable capacitors for my no tune lk500.
    I tried getting the Id off a friend's lk and the Id looks like it may be BOAPL500E. Not sure about the first two characters. They could be 80, but I think they are BO.

    Any help much appreciated.

    I would love to locate a dead LK500NTC for other parts needed. Thank very much in advance
    K1SR Rob IMG_1779.jpg
  2. W1QJ

    W1QJ Ham Member QRZ Page

    Rob, I think I have what you need. Is what you need what I see in this photo?
  3. K1SR

    K1SR Ham Member QRZ Page

    Yes. I need the two variable capacitors you see in the photo.
    Tell me how much and I will send you the money.
    Thanks so much
  4. K1SR

    K1SR Ham Member QRZ Page

    Louis, the pic is a friend's amp with the correct variable capacitors.
    Someone replaced them in my amp with a different brand and one of them the shaft moves in and out. So I'm hoping to replace them with the correct caps.
    Someone really got in the amp that had no business being in there.
  5. K1SR

    K1SR Ham Member QRZ Page

    OK, I did get the correct information and these are the two variable air capacitors I am looking for.
    80APL50DE. These are 10 to 50 pf rated 3.3KV with
    .080 spacing.

    Thanks for looking
    K1SR Rob

  6. W1QJ

    W1QJ Ham Member QRZ Page

    That is because these caps usually get RF burned when somebody uses the amp outside the area of the band that the amp has been pre-loaded for. I see these caps burned more often than not on these amps.
  7. W9GB

    W9GB Ham Member QRZ Page

    Rob -

    Oren Elliot Capacitors - APL capacitors
    Edgerton, Ohio
    Largest manufacturer of air variables (USA based), outside of China.

    APL Features:
    Used as a tuning capacitor in a variety of RF test equipment and ham radio gear.
    • Low price
    • High maximum voltage
    • Large capacitances
    • Low-leakage L4-grade ceramic
  8. W9GB

    W9GB Ham Member QRZ Page

    APL Group

    Oren Elliott Products 80APL36DE (photo above)
    Air Gap:0.080 inches
    Min Cap:9pF
    Max Cap:36pF
    Max Voltage:2000

    The 80APL36DE is an off-shelf part (Internet order). $54.00 USD.

    Contact them for lead-time and price for the 80APL80DE model you require.

    APL Options:
    • Single-hole mounting
    • Mounting posts
    • Lock bearings
    • 80° rotor stop
    • Solder lugs for electrical connection to the stator
    • Insulated shaft.
    APL Variation:
    The APL-DE model, is a "double-ended" APL. The rear ceramic adds strength and rigidity, and is necessary on extremely long APLs with close spacing, like the popular 32APL208DE (.032" air gap, 208pF maximum capacitance). We currently offer five standard air gaps, whose corresponding maximum voltages range from 600V to 1500V.
    Last edited: Dec 24, 2016
    W1TRY and KD2ACO like this.
  9. K7GLD

    K7GLD Ham Member QRZ Page

    As a "perhaps" help to others with the LK500ntc amps, if/when the caps get RF burns/blisters, they can often be carefully filed down at the burn spots with a thin file - like the old "points files" used in old cars, and still available at NAPA and similar auto parts stores - but you MUST be meticulously careful that ALL filings are removed, and don't get lodged in other nearby caps rotors/plates.

    Next possible fix, is that if damaged area is near one end of cap rotation, rotate the rotor section to opposite undamaged side of rotation, and carefully retune for band(s) needing fix...
  10. AA7QQ

    AA7QQ Ham Member QRZ Page

    Harbour Freight (And the like) have small file kits with 10 different profiles for under $10. At my (Former) job, we used them all the time.
    After filing, I wonder if polishing with scotchbrite pads might be a good idea?


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