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Heathkit SB-200 Amp upgrade

Discussion in '"Boat Anchor" & Classic Equipment' started by KM4HNF, Jun 11, 2018.

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  1. KM4HNF

    KM4HNF Ham Member QRZ Page

    Decided to upgrade my sb-200 amp with the Harbach stuff. Just installed the Power supply conversion. Went well.
    Also installed the soft-key board, which also went well.
    I bought the Transmit/receive relay at the same time, but wondering if I really need it. I know they say if it ain't broke, don't fix it!!!, but... My question revolves around the fact that the relay really didn't have any instructions, and it looks somewhat different than the original. Not certain how to proceed, or if I SHOULD proceed with the new one. Pros and cons, if any , appreciated.

    On a different note, on my SB-102 transceiver, doing some recap, and on top of the LMO, are two electrolytics in metal type cans, 500MFD at 25 VDC I think, Do these metal clad caps fail over time like the paper ones, requiring replacement? Info appreciated.

  2. KI4AX

    KI4AX Ham Member QRZ Page

    Hello RJ:

    I upgraded my SB-200 a couple of years ago and used the Harbach mods. I also replaced the Relay due to it's age and condition. I don't remember having any issues with the new relay and it was pretty much a direct replacement except for having to change the value of a resistor. The decision to replace the relay should be based on the condition of the existing relay. If it shows much wear I would go ahead and replace it, while you have the cabinet off, since the original relay is pushing 50 years old. If you get stuck I'm sure someone here on the Zed will be able to help you.

    Yes, those caps do go bad over time. They suffer the same degradation the paper ones do. They dry out and short out. Usually a cap will start heating up if it is going bad so if the cans are getting warm they are on their way out. Again, I would replace them as a matter of preventative maintenance. The old ones can be left in place to maintain the original 'look' by installing the new ones at the bottom of the cans in the under chassis.

    Good luck and have fun...

    Dan KI4AX
    KD2ACO likes this.
  3. W1BR

    W1BR Ham Member QRZ Page

    Electrolytic caps are constantly reforming (leakage currents) when in operation. It is a chemical reaction, thus electrolytic caps have a finite operating lifespan that can be as low as a few thousand hours when run at maximum ratings (temperature, ripple current, etc.) Old electrolytic caps can be tested for ESR, leakage and capacitance, but it is often better to simply replace questionable caps when they are encountered. Unfortunately, there is a wide variation in the quality of vintage electrolytic cap brands... some failed within a few years, others will still test and perform like new. Sprague caps are generally reliable, Aerovax was junk from day one.
  4. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Sometimes, electrolytic cap age is a hot topic around here.
    My system for gauging electro-life is to look at the stopper and read the date code. Dry stoppers with signs of electrolyte leakage= replace.

    If the stoppers look OK, then the date code comes into play:

    <20years= :)
    20-30y= o_O
    40 years? :(
    over that? The cap probably doesn't owe you much. :oops:

    It may work ok if it has been in regular use, but I don't expect too much out of them.
    50y+? Foggettaboutit. :p
  5. KM1H

    KM1H Ham Member QRZ Page

    And no date code means it is even older.

  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Pffffft, BLAM! :eek:
    KM1H likes this.
  7. KI4AX

    KI4AX Ham Member QRZ Page

    Small mushroom cloud slowly rises from the amp.....
    KM1H likes this.

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