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Sb200 tube makes clicking on 10 meters

Discussion in 'Amateur Radio Amplifiers' started by KB3SQW, Nov 20, 2018.

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  1. KB3SQW

    KB3SQW Premium Subscriber QRZ Page

    Well my relay was not making noise it is a tube . I replaced them with new still some issue. All other bands ok . Can a band switch cause this . Not sure where else to go.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Turn the lights out and see what is arcing.

    Use a dummy load

    Good Luck.
    K7TRF likes this.
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Sure, a band switch, a bad connection somewhere, an issue with the loading or tuning caps arcing to ground. Could be a lot of things. Try what Don suggests, operate the amp on 10m into a dummy load with the outer amp cover removed and turn off the lights to try to see the actual arcs. That should help you pin down the cause but since it's only happening on 10m, the band switch is a good guess.

    If you haven't already done so, DON'T use Deoxit on the band switch contacts inside the RF cage, any residue it leaves is a sure way to get HV arcing. If you, or someone else, has already done that or you can see arcing near the RF cage bandswitch contacts then clean it up with high concentration alcohol and inspect the actual switch to see if the ceramic is cracked or the contacts are charred from previous arcing. But start with Don's test to narrow down the problem area.
    WA7PRC and KI4AX like this.
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Everclear works good for cleaning if you have it on hand.

    Only drink it to celebrate the fix, After the cover is back on. :)
    WA7PRC, W1TRY, KI4AX and 2 others like this.
  5. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    J├Ągermeister leaves too much residue in there.
    K0OKS likes this.
  6. KI4AX

    KI4AX Ham Member QRZ Page

    It will be hard to get at, but check at the bottom of the band switch (inside the RF cage). If someone tried to clean the band switch, with contact cleaner (like DeOxit), the dirt and grime probably ran down and concentrated near the bottom. There is a bolt (threaded shaft) that holds the band switch wafers together at the bottom and the gunk will cause a short from that bolt to the closest contact - which is really close to the bolt. If that IS actually the issue I doubt you will see it even in the dark because you can not view the bottom of the band switch wafer from the top of the amp. There is a hole in the chassis directly under the band switch and you MIGHT be able to view the arcing through the hole if you flip the amp upside down.

    Carbon trails are difficult to stop once they get started. If you DO have a carbon trail going you will most likely have to change the band switch wafer. They can be purchased from Harbachs.

    Had that issue with my SB-200. I could hear the 'snapping' sound but had a really difficult time finding it because of the location. And, every time the short (snap) occurred it would destroy the soft key I had installed and the amp would lose its Idle Plate Current.

    If the amp is really dirty it is also possible there is a carbon trail between solder lugs on a terminal strip some where. Found one of those in my amp also.

    Dan KI4AX
  7. KM1H

    KM1H Ham Member QRZ Page

    Could also be a parasitic suppressor with cracked resistor and that usually happens on 10M. Replace both with an Ohmite 47 Ohm OY series.

  8. KB3SQW

    KB3SQW Premium Subscriber QRZ Page

    Ok I got it with a lot of help and learning.... I found the relay to be dirty and the band switch also both cleaned up . I also found the person that installed the sk in it put one red wire from it on the 2 terminal not 5 . After wiring and checking I got it . Thanks and sorry about the twin posts I thought I was chasing two things.
    KA9JLM likes this.
  9. WA9SVD

    WA9SVD Ham Member QRZ Page

    You can find 90% "rubbing alcohol" in most apothecary shoppes. (I.E. drug stores and many supermarkets.) Be careful though. Standard rubbing alcohol is only 70%, and the cheap discount stores now only have 50% isopropyl alcohol, and won't do the job. Obviously, the 90% alcohol is more expensive, but a pint bottle goes a LONG way.
    KC8VWM likes this.
  10. K8ERV

    K8ERV Ham Member QRZ Page

    Not when I'm thirsty!

    TOM K8ERV Montrose Colo
    KQ9J and WA7PRC like this.

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