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Amp supply LK-550

Discussion in 'Amateur Radio Amplifiers' started by W1CJF, May 23, 2019.

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  1. W1CJF

    W1CJF Ham Member QRZ Page

    So I just acquired a amp supply lk-550 with the 3 3-500s. The Parasitic Suppressors seem a little beat up and was wondering if there is a company that makes the horseshoe ones? It hasnt been used in a while so I'm going thru and cleaning up and checking anything before I plug it in. Does anyone make the pre built parasitic's? Thanks 20190519_162514.jpg
  2. N8FVJ

    N8FVJ Ham Member QRZ Page

    It was determined horseshoe (hairpin) are not as effective as the standard wire wound around a 47 to 100 ohm resistor with 47 being the best resistance at VHF frequencies. I also read ceramic type resistors work as well as carbon resistors. Replace the resistor.
  3. W1QJ

    W1QJ Ham Member QRZ Page

    I make my own all the time. I simply start with an NOS CC resistor that has the correct value and construct a "clone" of the original. Looking "beat up" doesn't necessarily mean they won't work. It all depends on the actual value of the resistor. After 40 years of use they may drift and change value from heat. If there is a question, making clones with known good resistors is the thing to do. Making something OTHER than what is on there may be a big mistake. You can't argue with success for 40 years. I view suppressors as a maintenance item like brake pads in a car. At some point it is due for a new set.
    VK6APZ, WA7PRC, KA0HCP and 3 others like this.
  4. W9GB

    W9GB Ham Member QRZ Page

    Last edited: May 23, 2019
  5. G4SSG

    G4SSG Ham Member QRZ Page

    did you notice the burn't out resistor on the control board ?
  6. AE4JA

    AE4JA Premium Subscriber QRZ Page

    Yep, under the pair of diodes on the lower left... I looked closer after you mentioned it. That amp is going to need a good "once over" before any power is supplied...
  7. W1QJ

    W1QJ Ham Member QRZ Page

    Those ALO boards in this amp are useless. Totally unnecessary, but if its there and works, ok.
  8. WA7PRC

    WA7PRC Ham Member QRZ Page

    ^ ^ ^ THIS^ ^ ^

    The LK-550ZC documentation specifies PC1-PC3 each as 3T 16ga on a 100Ω/2W carbon resistor. Ebay seller 'bigsmythe74' ( sells NOS Allen-Bradley carbon composition resistors for a (usually) reasonable cost. In this application, it doesn't have to be EXACTLY 100 Ohms... any value around 100Ω will be fine.

    I see 91Ω/2W is available for $1.25/ea plus $3.50/order shipping ( If you have your heart set on 100Ω, it'll cost you $4.00/ea ( plus $3.50/order shipping.
  9. W2WDX

    W2WDX Subscriber QRZ Page

    Chris ... if you need three of these carbon comp resistors I literally have hundreds of this value NOS, both AB and Ohmite. Just let me know. I can QC for value and mail a bunch up to you. Don't worry about money, like I said I have more than a lifetime supply and I think it's a crime what people are asking for these nowadays.

    I would also suggest "uping" the wattage rating on that resistor on the control board. I have seen this several times on these amplifiers and they were probably underrated by the manufacturer due to available parts inventory.
    Last edited: May 25, 2019
  10. W1CJF

    W1CJF Ham Member QRZ Page

    Yea I still have some work to do on this before I even think about plugging it in.

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