Another SB-1000 band switch problem...

Discussion in 'Amateur Radio Amplifiers' started by K9DD, Jan 29, 2019.

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  1. K9DD

    K9DD XML Subscriber QRZ Page

    I obtained an SB-1000 amp that works on every band but 40 meters. I found the problem but can't figure out how to fix it. The band switch wafer SW2C is supposed to switch in C26 (170pf) on 160 only, mine switches it in on 40. I have a carcass from a parts amp that is wired correctly. It looks like the wiper is off by several degrees. I took it apart far enough to move the wiper to the correct position but when I do that the wiper will not go on he shaft. The only way it fits is when it is in the 40m. position. I can't figure out how to fix it. Looks like the wafer was manufactured wrong.

    If there was an easy way to move the entire tank circuit from the parts amp to the good one I'd do that. It would be easy if the band switch could be removed in tact but it doesn't look like that is possible. The 160 meter input coil is burned badly on the donor amp.
     
  2. W9GB

    W9GB Ham Member QRZ Page

    Damaged band switches are common with used SB-100o HF amplifiers.
    Proper Alignment of Multiple Rotary Wafers have been an issue since first usage with 1940s shortwave receivers. Previous service attempts of rotary wafer switches can make a real (expensive) mess. Requires patience.

    Replacement Wafers (CentraLab, ElectroSwitch) and Tank Circuit Parts can be acquired from Ameritron/MFJ ... silver plated parts require quality Silver Solder.
    http://www.electro-nc.com/productpages/rotaryswitches.shtml
    Ameritron/MFJ services the Heathkit SB-1000 amplifier (see below) using AL-80B parts.
    CONTACT Ameritron/MFJ for your Individual Part Needs (wafers, coils, etc.)

    Ameritron AL-80B uses a 3-section ceramic band switch (part # 500-2135), $102.00
    http://www.ameritron.com/Product.php?productid=AL-80B
    The Tuned Input Wafer, S201, is sold separately (part # 500-4811), $31.85
    ===
    In Case you were Unaware .....
    HeathKit SB-1000 Repairs

    Ameritron now offers professional repair services for the HeathKit SB-1000 amplifiers.
    http://www.ameritron.com/heathkit.php
    To have your unit repaired by us, please ship it to: Ameritron, 116 Willow Road, Starkville, MS 39759.
    IF your tubes are okay, you can keep them. If you are not sure if your tubes are working properly or not, ship them in a separate container. Please include a note describing your problem with the unit as well as a phone # and/or email address that we can contact you at. We will give you a estimate on our repair costs by phone or email.
     
    Last edited: Jan 29, 2019
  3. W1QJ

    W1QJ Ham Member QRZ Page

    The wafer that switches in the added padding on 160 meters usually get toasted in that amp because Heathkit did not have you install the corona washer. Hence most SB-1000 amps that get used on 160 have this wafer toasted. I fixed many of these so far. Apparently someone found a wafer that looked right but as you say the indexing is not right. That person put on that wafer and then realized after it was back together that it was all wrong and then sold the amp to you. I have made my own wafers for this use in the past as it is hard to find the right one.
     
  4. K9DD

    K9DD XML Subscriber QRZ Page

    Thanks for the info. The wafer on the parts amp appears ok so I'll probably use it, maybe the whole switch.
     
  5. KN4CTD

    KN4CTD Ham Member QRZ Page

    Is it possible someone has the wafer installed flipped around 180 degrees (backwards)?
     
  6. WA7PRC

    WA7PRC Ham Member QRZ Page

    That occurred to me, too (bassackwards installed been have might wafer The). :p
     
    K9ASE likes this.
  7. KN4CTD

    KN4CTD Ham Member QRZ Page

    I’ve never personally seen it but have heard of it before. I guess it could be easy to make that mistake and still have something that works.....sort of
     
  8. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    I have seen it where the wafer was flipped top to bottom, side to side, and various other combinations... Sometimes someone will use the wrong switch count wafer too!

    If you have a good wafer, draw a diagram of the orientation, then redraw it to be sure of the diagram, then pull the improper wafer and see if you can use it in another orientation and have it work. If all else fails, sell it on ebay as untested... XD

    I had burnt contacts on my band switch, but I was able to use a set of unused contacts by drilling out the rivet and using 2-56 hardware to remount it where it was needed.
     
  9. W1QJ

    W1QJ Ham Member QRZ Page

  10. W1QJ

    W1QJ Ham Member QRZ Page

    In the above photo you can see the corona washer. You need to add that washer when you finally get the right wafer. The rear wafer comes off easily by doing some disconnecting, the next two wafer come right off to get at the back one which is your concern. If your rotor is not bad but just the contacts, you can put new contacts on like I and the fellow above mentioned.
     

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