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SB-200 Damaged plate on "TUNE" capacitor

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

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  1. AF6LJ

    AF6LJ Ham Member QRZ Page

    That's funny :D
    Besides arn't those suppose to be good watches?
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Probably, but I've had this one a really long time. I think it died of old age.
     
  3. KM1H

    KM1H Ham Member QRZ Page


    Youre right, guess I always missed that step and so did many others as most I get in here are on the inside. If I have to drop the panel the hardware goes inside if it was on the panel.....simple common sense.

    Just checked the 220, 221 and 2200 manuals are all the same there.

    DUMB!
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I thought so. I never thought about keeping the washer and nut on the tuned input subchassis because it would act like a "spacer" and keep the front edge of that away from the panel. Thinking about it now, that probably doesn't really matter.

    I'll try it your way next time I have to mess around with one.
     
  5. KM1H

    KM1H Ham Member QRZ Page

    It does bow the panel ever so slightly but its not noticable all buttoned up. I used to grumble about that and blamed Heath.
     
  6. W1QJ

    W1QJ Ham Member QRZ Page

    There is no doubt that without a nut on the inside if the outer nut gets loose the calibration of the switch can change and wreck havoc on the contacts. I carefully line up the contacts and tighten the outer nut on the front panel. Sure would be nice to have a nut on the inside. I can live with a slight bulge over a burned switch.
     
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    That's really easy to fix with a step drill, and nobody is the wiser until they take the bandswitch knob off.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Actually, a switch index with a forward facing (towards the knob) washer having a 90 degree blade (prong) sticking out 1/4" or so can physically "lock" the switch in position against the chassis or panel so the bushing can't possibly rotate, ever -- at least not accidentally. This is a five-cent item they could have used, and is used on many rotary switches.

    <Sigh>

    Oh well, if I were building an SB-200 or -220 from scratch today there are many things I'd change in the assembly process, including adding reduction drives to both controls. They were really cheap in 1975 and they're still cheap today. Plenty of room for them. I'd split the outer cover into two so the top half and bottom half are individually removable (just about "zero" added cost), snap on a STANDBY switch on the back end of the REL OUTPUT power pot (these used to cost $0.95 each from Centralab back in the day), and use low voltage keying (which really would have been exactly zero extra cost if done from the start).

    Funny thing is, they're still good amplifiers. Just not fully hatched.
     
  9. W1BR

    W1BR Ham Member QRZ Page

    Another major FUBAR was not having the 4-40 wafer hardware extend through all of the wafers. It was possible for the front indexing
    mechanism to move, along with the input filter wafer, while the PA tank wafer remained firmly attached to the rear Al. housing of the
    input filter shield. You had to very careful when tightening that nut to be sure everything was in alignment. BTW, I had thought about adding
    a pot with a switch and tried it. Not enough clearance to the filament transformer. Its tight back there. Next move might be using a different
    Rel/Grid/Voltage switch that has two poles and four positions to put the amp in standby.
     
  10. KJ4AQU

    KJ4AQU Ham Member QRZ Page

    Finally I have the replacement TUNE cap and will replace this weekend. Problem is I have no Transceiver to test. Also on a somewhat related question whcuh verniers do you all recommended be used on this amp? Thinking of adding one.

    Also KA5S interesting idea about using varnish (clear finger nail polish)
     
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