SB-200 Damaged plate on "TUNE" capacitor

Discussion in 'Amateur Radio Amplifiers' started by KJ4AQU, Apr 1, 2012.

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  1. W1BR

    W1BR Ham Member QRZ Page


    Here's what I did in my SB-220.

    http://i271.photobucket.com/albums/jj129/k1zjh/DSCF1452.jpg
    http://i271.photobucket.com/albums/jj129/k1zjh/DSCF1434.jpg

    The vernier drive is probably an old Jackson Brothers drive I had stored in my 50 years of accumulated
    junk-box collection.

    The shaft on the Heathkit tune cap had to be cut back. The drive mounting ears directly aligned with
    existing tapped 6-32 screw holes in the capacitor frame. A metal standoff is used a spacer to mount
    the reduction drive to the capacitor frame.

    You have to use a step drill to open the shaft hole on the front panel so that the face of the reduction
    drive fits through the opening. Some sort of dial pointer needs to be mounted on the drive face to show
    the capacitor position on the SB-200 front panel markings.

    There is a possibility most of these items could be obtained from Ameritron, since they probably use
    similar parts to provide vernier tuning on their amps.

    BTW, I had some arc damage on both variable caps. Both were cleaned up using flat jeweler's files,
    and have been working fine ever since. I wouldn't be too quick to discard that damaged tuning cap.

    Pete
     
    Last edited: Apr 6, 2012
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    6:1 planetary reduction drive for 1/4" shaft devices is $10.95/each new, here: http://midnightscience.com/catalog5.html

    That's actually not a bad price. I get them from my local surplus store for about $5/each, but they're usually "used," removed from equipment.
     
  3. W1BR

    W1BR Ham Member QRZ Page

    Wow, that is a good price, and I like the brackets! I'm going to order a few for future projects.
    Tnx for that link!!!!
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    If you can adjust it as-is, none. Why add cost & labor if it works without it? I've been using my SB-220 since the early 70s w/o it (on 80-10m), and don't find it at all tough to adjust. You can always add it later, if you find it tough to adjust.
     
  5. KJ4AQU

    KJ4AQU Ham Member QRZ Page

    WB2WIK -- 6:1 planetary reduction drive for 1/4" shaft devices is $10.95/each new, here: http://midnightscience.com/catalog5.html

    Wow not a bad price. Looks like the one used in the Hw-101. May have to get one.

    The main reason I want one is the 10 & 15 are very touchy. And these old hands aren't as steady as they used to be.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I agree with you. I built my SB-220 in about 1976 or something when I was in my mid-20s and my hands weren't shaky at all, and I still found it to be a pain in the butt to tune on 10m, and maybe 15m also. Just "no reason" for what they did, when those planetary drives were just a couple of bucks each back then and other amps (Swan-Drake-etc.) all had them and sold for only a bit higher price point (difference between a kit and a factory wired model made them about equivalent).

    After building my SB-220 I went on to own several similar amps made by Henry. Pretty big difference. Much nicer designs both electrically and mechanically, and they really weren't much more money. But you live and learn!
     
  7. WA7PRC

    WA7PRC Ham Member QRZ Page

    The HW101 (like my SB-102) didn't use planetary drives for PA tuning. PA tune and load controls have 180° rotation from min C to max C.

    The tuning knob range will go from 180° to 1080°. Unless you have a pointer attached to the tuning capacitor shaft, a planetary drive will make the band markings on the SB-200 front panel useless. When changing bands, you'll have to count turns.

    My hands also aren't as steady as they used to be but, retuning my stock SB-220 (after a band change) still takes only a few seconds.
     
  8. W1BR

    W1BR Ham Member QRZ Page

    A pointer is extremely easy to attach to the Jackson Bros. drives,
    and several on here have expressed dissatisfaction with the
    SB-220 and SB-200 tank tuning on the higher HF bands.
     
  9. WA7PRC

    WA7PRC Ham Member QRZ Page

    • The unit mentioned in this thread isn't a Jackson Brothers drive. I'm looking forward to seeing photos of either (with a pointer) in this application.
    • Several hams have expressed dissatisfaction with the sharpness of tuning. Thousands (including this ham) have not.
     
  10. W1BR

    W1BR Ham Member QRZ Page

    The pointer attaches to one of the screws on the front of the drive:

    http://i271.photobucket.com/albums/j...h/DSCF1434.jpg

    It isn't difficult. Virtually every amplifier made since the SB-220 was introduced uses vernier drives.
    Come to think of it, they all have pointers too.

    Adding a vernier drive on the tuning cap was one of the best improvements that could be done to that amp.

    Several thousand hams are not reading this read. Only ONE ham has made negative comments about using
    vernier drives on amps. Would removing them from the Ameriron designs be an improvement?
     
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