Thinking of getting an SX-71....

Discussion in '"Boat Anchor" & Classic Equipment' started by VE3GZB, Feb 24, 2021.

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  1. VE3GZB

    VE3GZB Ham Member QRZ Page

    I already have an SX28 and an HRO, so I was now thinking of looking for and getting an SX-71. I like the layout of it.

    I use these boat anchors just for occasional casual listening on HF, looking for a bit of DX and listening in on a ham band or two.

    Before I put any hard earned cash out I want to ask for any thoughts regarding the SX-71? Good? Bad? Ugly?

    73s, VE3GZB
     
    KA0HCP likes this.
  2. K0IZ

    K0IZ Ham Member QRZ Page

    Our radio club used to have one as its station receiver. I played with it a lot. Liked the styling, classy. Double conversion on upper bands. Crystal filter (good for CW, not great for SSB). 455 IF so otherwise fairly broad. As I remember was quite stable after some warmup.
     
    VE3GZB likes this.
  3. W5RKL

    W5RKL Ham Member QRZ Page

    The SX71 is a great receiver.

    There were several runs of the SX-71. The "White" dial SX-71 did not have 15 meters on the
    band spread dial. The 15-meter band was added to the Band spread dial in the Black dial SX-71.
    Other than the lack of 15 meters on the White dial SX-71s, the other runs of the SX-71 were
    basically the same. I have a RUN 4 version, Black dial. I picked it up on eBay a couple of
    years ago and it works great.

    The SX-71 is a single/dual conversion receiver.

    Bands 1 and 2 are single conversion with an IF of 455Khz
    Bands 3, 4, and 5 are double conversion with first IF of 2.075Mhz and second IF of 455Khz.

    You can download the operator manuals here:

    https://w5rkl.com/wp-content/uploads/2015/02/hallicrafters-SX71-User-Manual-1.pdf

    https://w5rkl.com/wp-content/uploads/2015/02/SX-71_Run4_JJB.pdf

    Service bulletins here:

    https://w5rkl.com/wp-content/uploads/2015/02/Hallicrafters-SX71-Service-Bulletin.pdf

    https://w5rkl.com/wp-content/uploads/2015/02/Hallicrafters-SX71-Service-Bulltin-1950-109.pdf

    If you purchase an SX-71, check the multi-capacitor C61, it more than likely if it has not been replaced
    then I recommend you replace it along with the paper capacitors (hard plastic/wax coated capacitors). hayseedhamfest.com
    has an SX-71 capacitor kit, a wise investment.

    The SX-71 does not have an inline fuse so I recommend adding a fuse holder with the properly rated fuse mounted below
    the chassis. A 1.5 amp fuse will protect the receiver. The chassis is "steel". I use a single fuse holder such as the one shown
    below. Drill a single hole to allow a 6x32x1/4" machine screw and 6x32 machine nut and #6 lock washer to mount the
    fuse holder to the inside rear side wall. Connect the "AC HOT" to one fuse holder terminal and the other fuse holder
    terminal connect to the main ON/OFF switch. You can replace the 2 blade power cord with a 3 wire grounded
    power cord (the Black wire is AC Hot, the WHITE wire is AC Neutral, and GREEN wire is safety ground). The green
    wire connects to the SX-71 chassis.

    73
    Mike W5RKL

    [​IMG]
     
    Last edited: Feb 24, 2021
    N2EY, VE3GZB, W7UUU and 1 other person like this.
  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    For those of us unfamiliar...

    What cost $179.50 in 1949 would cost $1,980.28 in 2020.

    "The SX-71 is a 5 band communications receiver covering AM broadcast and shortwave from 538 KHz to 34 MHz in four overlapping bands. A fifth band covers 46 to 56 MHz directly on the bandspread dial which is also calibrated for the 80, 40, 20, and 10 meter ham bands. A later version, Run 4, also has calibrated bandspread for the 15 meter ham band. The left slide-rule dial is the main tuning dial and the right slide rule dial is for bandspread and the 6 meter band."
    Courtesy of: https://people.ohio.edu/postr/bapix/SX71.htm
    [​IMG]
     
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  5. W5RKL

    W5RKL Ham Member QRZ Page

    There are a few SX-71s on eBay, one has the front panel painted an ugly "Orange".
    Prices range in the low to mid $200 range. There's an SX-71 on eBay with a current bid price of $303.
    Looking at it, there's no 15-meter band on the band spread dial so that's most likely a Run #3.
    There's an SX-71 on eBay with a Buy it Now price of $249. I can see the faint "RUN 4" stamped
    on the chassis and it has 15-meters on the band spread dial.

    The speaker terminals are rated at 500 ohms or 3.5 ohms. An 8-ohm speaker will work. A large
    8 inch or 12-inch woofer really works great. The R-48 speaker works very well as does the
    R46B and PM-23. I use the R48 and PM-23. My PM-23 has an 8-inch 8-ohm woofer that
    sounds great.

    If the receiver powers up but the dial lamps and tube do not light up, check the rear octal socket for
    the octal jumper plug. Pins 6 and 7 must be shorted to allow 6.3VAC to power the tube filaments
    and the dial lamps. If the lamps and filament are lite but no signal heard, check the front panel
    RECEIVE/STANDBY toggle switch needs to be in the RECEIVE position.

    The V7 local oscillator 6C4 has a tendency due to age to fail at the bottom end of the broadcast band.
    When tuning the broadcast band below 700Khz, V7 would stop oscillating even when aligning that
    band. Replaced V7 with another 6C4, problem solved.

    73
    Mike W5RKL
     
    VE3GZB likes this.

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