SB-220 Filter Capacitor replacement fit

Discussion in 'Amateur Radio Amplifiers' started by KD5YPH, Dec 17, 2015.

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  1. KD5YPH

    KD5YPH Ham Member QRZ Page

    Quick update...
    1. I realized after the fact that I had the board upside down in the photos above. I was in a hurry and wasn't paying attention but it does not fit the correct way either.
    2. After some more thought, I tried creating my own mounting bracket with some cheap cutting board material and discovered that the bottom of the PCB was hitting the chassis. After some dremel work, it no longer hit the chassis but still doesn't give me enough room to tighten everything down.
    3. Someone suggested adding standoffs which I'll add into the mix to try.
     
  2. KM5FL

    KM5FL Ham Member QRZ Page

    Judging from the photos and your description, it appears the whole mess is ill-designed.. I was using Harbach Electronics' components when Allen Harbach was alive. Harbach's original designed filter block didn't use those spacers or the snap-in capacitors. Some of the components used back then are becoming obsolete, so Jeff has re-designed some things.. Normally their stuff fits as intended but something went wrong here..

    Rather than modifying anything, I suggest you contact Jeff and let him work it out for you..

    KM5FL
     
  3. KC2PMM

    KC2PMM Premium Subscriber QRZ Page

    Agreed. This is supposed to be a bolt-it-in type of upgrade. Something is not right. Call Jeff. You should not be having this much of a problem.
     
  4. N5SMO

    N5SMO Premium Subscriber QRZ Page

    Is there any issue (other than originality) with skipping the plastic spacer blocks all together? Wouldn't the caps run cooler exposed to airflow? I guess what I am trying to understand is "what is the purpose of the plastic spacer blocks?" Arc prevention or to prevent bulging perhaps???
     
  5. W1QJ

    W1QJ Ham Member QRZ Page

    Be sure you are not trying to fit the caps all the way in. Most caps have a slight ripple just behind the top edge where the pins are. DO NOT try to get that part of the cap in the shells, that ridge is ever so slightly larger in diameter and it won't fit, that should be exposed.
     
  6. N5SMO

    N5SMO Premium Subscriber QRZ Page

    With the W7RY board and the shorter 450V caps, do you have to use the plastic surround blocks at all? what is their function? They will fit ok, I am just trying to understand what their purpose is.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    You don't have a W7RY board. You have the board sold by Harbach. Although they are basically all the same of that type. You have to loosen the U shaped hold down bracket, that means removing the nuts underneath so you can lift the bracket up high enough so you can slip the cap and shell assembly in place on the chassis and then come back down on top with the bracket. YOU CAN NOT SLIP THE CAPS IN THE SHELLS WITH THE SHELLS IN PLACE IN THE AMP. You have to slide the shells on individually and leave the cap ridge out or they won't fit. Then like a sandwich lay them in place on the chassis and then slide the U bracket down over and hold in place while putting the screws back in on the bottom. I have never had to do any razor blade work unless the caps are too big.
     
  8. W7RY

    W7RY Ham Member QRZ Page

    How did this ever work in the first place?

    The screw studs are too short to fit through the chassis with the plastic cap blocks without the capacitors according to your pictures.

    Are these plastic cap blocks and the aluminum bracket from different amplifiers? They must be.

    Best solution is to make the studs longer. You can make a longer one by using a crimp on lug and crimping a long 6-32 headless screw into the lug. Then screw the lug onto the aluminum cap holder bracket. Looks like the original studs are riveted onto the bracket? If so, you'll have to drill them out, and use flat head screws and countersink them on the inside.

    Good luck
    73
    Jim W7RY
     
  9. K7RJB

    K7RJB Ham Member QRZ Page

    SLPX331M450H5P3 are the 330 caps I used with my Harbach board the caps fit fine, you cannot fit the caps all the way into the plastic holder. The rolled end of the cap is larger than the body. So a little less than 1/8" of the cap sticks out of the holder.
    I also spaced the resistors off the board a little to provide some thermal relief.
     
    Last edited: Jun 26, 2019
  10. N5SMO

    N5SMO Premium Subscriber QRZ Page

    What is the purpose of the plastic holder blocks? That is what I am trying to figure out. What function do they server?
     

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