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HEALTHKIT SB-220 glitch resistor Mod?

Discussion in 'Amplifiers' started by cbkidd1, Jul 3, 2021.

  1. cbkidd1

    cbkidd1 Well-Known Member

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    Hello,
    I would like to do the glitch resistor mod to my SB-220. My question is will an Ohmite B20j10RE 10Ohm, 20w, 5% resistor be enough protection? And where would be the best place to install it. And are there any other mods I should do to safeguard the new tubes and transformers? 73,


     

  2. nomadradio

    nomadradio Analog Retentive

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    There is a wire that runs from the meter/rectifier board to a ceramic feedthrough bushing at the top of the divider wall. Replace that wire with the glitch resistor.

    Making a 20-Watt resistor fit in that spot may be awkward.

    73
     
  3. cbkidd1

    cbkidd1 Well-Known Member

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    Hello Chris,
    I thought you would be the one to help me as always lol. So I will remove the blue wire coming off of the meter/rectifier board. And put the glitch resistor in its place. By the way that is the old meter/rectifier board. I am feeling better now so I wanted to get started on the repairs. While I was at it I wanted to find out if there were any other mods I should put in place to protect the tubes and other parts of the amp? I think there is one for the relay? I have it wired for 120vac. I also took a few photos and was wondering if you might know what the black box with the relay on the underside of the amp is for? I have no clue.73,
     

    Attached Files:

  4. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    That "Black BOX" is not stock! Guessing "someone" changed the relay from the 120 volt coil the original had. Used a friken wall-wart for power supply!:(
    Looks like the 120v Bias supply has been modified also. Could be fine, but those taped up connections "bother" me IMHO:eek:
    Other wise...new caps and Harbach rectifier/meter boards come to mind as something I would do.
    Also upgrade Hi-volume fan mod...
    My 2 cents
    All the Best
    Gary
     
  5. cbkidd1

    cbkidd1 Well-Known Member

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    Hello Gray,
    Been a while how are things? That is not what I was hoping to hear. Why would anyone want to change it? I thought the bias mod was done by moving two of the wires on the relay? I have been using it running on 120ac in CW mode. With about 90 watts of drive and it had been working fine until the cap bank had moved and shorted the bleeder resistors to ground. Lucky for me Chris helped me check the transformer out and it was found to be ok. I just got done replacing the caps Bleeders and meter board. I just need to install them.
     
    #5 cbkidd1, Jul 4, 2021
    Last edited: Jul 4, 2021
  6. cbkidd1

    cbkidd1 Well-Known Member

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    Ok, I looked over that black box and found that it indeed is a power supply. And I followed the two wires coming off of it over to the power switch for the amp. Then I went back and traced the blue wire from what looks like a relay board mounted on top of the power supply. It goes to the back of the amp and is wired into the ant relay plug? Why do people do these things to nice amps? Should it be taken out? Here are a few more photos.
     

    Attached Files:

  7. nomadradio

    nomadradio Analog Retentive

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    I'd guess it's a hillbilly soft key.

    The factory relay has a coil that requires 110 Volts DC to activate. And that's the voltage appearing on the center pin of the relay jack in the rear.

    A lot of newer radios will not tolerate a voltage this high connected to the radio's 'external amplifier' keying feature. I have seen more than one Yaesu FT757 smoked this way.

    The wall wart that's been installed with a relay plastered to its rear is probably there to carry the factory relay's switching, with a much-lower voltage now appearing on the center pin of the relay jack on the amplifier's rear panel.

    Not sure what other purpose it might serve.

    73
     
  8. cbkidd1

    cbkidd1 Well-Known Member

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    Thank you, Chris,
    That's kind of a relief. I had been using it with my FT-102 Transceiver. I have been looking at other mods for the SB-220 and one was the relay mod for 220vac. If I was to switch over to 220vac? Would I need to switch any of the wirings on the relay? Almost forgot I also want to add the Diode mod to the meters. Would it be ok for me to use 10A10 Diodes? I just happen to have a few extra from a Dyanco VTA-ST120 tube stereo amp kit that I am building. Thanks, Chris, for everything you have helped me with over the years. 73,
     
    #8 cbkidd1, Jul 5, 2021
    Last edited: Jul 5, 2021
  9. cbkidd1

    cbkidd1 Well-Known Member

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    Well, I got the new caps and bleeder resistors along with the new metering board. New tubes and glitch resistor installed. And oiled the fan. Wired for 120AC. All seems to be working just fine. I am keying around 40 watts from the transceiver with the SB-220 set to CW and seeing around 225 watts unmodulated from the SB-220 and getting around 600 watts with modulation with around 100ma or so on the grid. On 11 meters.Thanks for the help.
     
  10. nomadradio

    nomadradio Analog Retentive

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    Rock on! Gotta love it when a plan comes together.

    Where did you get the meter board? If it was Harbach you timed it perfectly. He's out of action since his basement flooded. And if you got it somewhere else, that's valuable info. At least until Jeff gets his business reconstructed.

    73
     
    #10 nomadradio, Jul 25, 2021
    Last edited: Jul 25, 2021
  11. cbkidd1

    cbkidd1 Well-Known Member

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    Hello Chris,
    I am sorry to hear about jeff's basement being flooded. Sure hope most if not all his electronics and other stuff is ok? I bought all the parts from Jeff except for the Glitch resistor and tubes back in May of this year. With having heart trouble and vacation. I did not get around to getting the whole thing done till Last week. I also like to take my time and go over my work a whole lot of times to make sure I do things right. I think with your help there is not much I can't do when it comes to the radio gear. For that, I am very thankful and grateful. All I need to finest now is the Dyanco VTA-ST120 tube amp kit. I bought it as my Birthday gift. And believe it or not, I also paid for my birthday dinner for my family and me at a cost of $220.00, And here I thought this is what others do for you on your birthday? lol.
     
    #11 cbkidd1, Jul 25, 2021
    Last edited: Jul 25, 2021

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