A remote Power Supply for the SB-220

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Apr 26, 2017.

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  1. AF6LJ

    AF6LJ Ham Member QRZ Page

    He can do it but he has to provide a B- lead and a chassis ground.
    It doesn't matter how or where he does it,
    He needs both a B- and a chassis ground.

    For those who may have forgotten their basic electronics....
    The cathode current in this amplifier is in series with the center tap of the filament transformer which has B- connected to it.
    The grid current is measured from B- to ground.
  2. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    On the HP240, I installed meters on the PS front panel. HV, Plate and Grid current. The issue is I won't be able to see the PS after it is installed and the actual amp will be 5 feet in the air above the operating position. So if the power output meter wiggles at all, the amp is working just fine.

    I wish I could install an intermediate Amp in the thing as the 736R only does 10W and I need the solid state amp to get up to 100W. Maybe a pair of 6146s but I don't have the PS for those. They would shoot out of the sockets with 3KV on them!!!

    I do like the twisted pair idea. One suggestion is to use CAT 5 Cable for the signal lines. K9YC emphasized at the talk on RFI he did at Visalia to use CAT 5 cable for signal runs. It is self shielding.

    so I might run a 4 wire cable up to the amp for the AC. I need to look at the docs on the W7RY and see where he gets his 120VDC I could rectify the AC on one of the primaries
  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    The FTDX-5000 doesn't do six meters??

    The power for the W7RY mod comes from the bias winding on the SB-220/221 filament transformer.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The FTDX5000 does do six meters, but its receiver is not up to the FT-736R. Pat's already reported on that, and I've found the same thing.

    However...he could use the 5000 for TX and the 736R for RX! Or possibly make changes in the 5000 to improve its six meter performance. I have no idea how possible that might be (complicated rig).

    One of the big problems in the "HF+6 meter" transceivers is they did really nothing to optimize 6m performance. The transverter in the 736R is amazing. It's well optimized just for six meters, since that's all it does.

    I see the QST Product Reviews for the two rigs (on six meters) indicates the FT-736R measured -140.5 dBm MDS with a 600 Hz CW IF filter (no preamp, just the receiver). Same type review for the FTDX-5000 indicates -120 dBm MDS with a 500 Hz CW filter (also no preamp).

    That's a world of difference! Now, you can engage a preamp on the 5000 to improve that (736R doesn't need it), but then IMD and BDR worsen.

    I can see why Pat would lean towards the 736R for 50 MHz use, but for every problem there's a solution.:p
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    Makes sense to me, and the MDS on my IC-756 wasn't that great on six ether.
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    Looks like Pat needs a 120W IPA
    That is not hard to find or build.
  7. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    I have a 100w solid state amp that I can use, but it would be nice to incorporate it into the SB221
    So I got those files on the W7RY, tnx Sue.
    I can use 2n2222s for the 2n3904s. Have most of the caps, probably the resistors except the power resistors. But will hafta order the zeners and tl-431 and mpsa42and tip47. So more from Mousey Wouser
    AF6LJ likes this.
  8. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    That W7RY board is pricey! Might just scratch build it on a perfboard
    AF6LJ likes this.
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    It's not that pricy :rolleyes:
    There is a high voltage power transistor in there.
    The original parts are not that expensive.
    Don't forget the MOV ether...
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    You really can't do that, some of the transistors have higher breakdown voltages than the 3904s and 2222s...
    Not all the parts mount on the board.
    The main switch transistor doesn't. and two (or maybe three) of the resistors that connect to the relay coils don't also.

    By the way...
    I have many 24VDC DPDT relays....
    I tossed six of them in a bag along with some useful documentation and that shielded plug for you to try on the inverter....
    Now all I have to do is remember the bag tomorrow.

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