Allied SX-190

Discussion in '"Boat Anchor" & Classic Equipment' started by N4KDF, Apr 30, 2021.

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  1. W5RKL

    W5RKL Ham Member QRZ Page

    I had an AX-190, ham bands only receiver a few years ago. I no longer have it but when I had it I removed C89 and R91,
    threw them in the trash. I then replaced the 2 blade power cord with a 2 blade polarized power cord, connecting
    AC Neutral to the power transformer primary winding where C89 and R91 were connected and AC hot to the
    other power transformer primary winding lead. If you keep C89 and R91 and switch to a 3 wire grounded power cable, that's
    entirely up to you. If you connect the polarized power cord correctly you won't have the AC power on the chassis problem.

    It's important to know that the AX/SX-190 receivers do NOT switch OFF the AC power to the power transformer. As long
    as the power cable is plugged into the wall outlet, there will be AC power applied to the power transformer regardless of the
    receiver's main ON/OFF switch position. There also is NO fuse in the power transformer primary. The only fuse in the
    receiver is in the B+ supply output that powers the receiver. I recommend installing a fuse in the AC Hot side of the
    power cord connected to the power transformer lead. A 1/4" amp fast blow fuse should work.

    Added comment:

    You should purchase a book on Basic House Wiring so you learn how your house wiring
    and wall outlets are wired to the house breaker box and how AC Main power is provided
    to the house breaker box from the power pole or underground AC power source. The book
    will show how individual AC circuits are wired in your house.

    Mike W5RKL
    WA1GXC likes this.
  2. W5RKL

    W5RKL Ham Member QRZ Page

    If you replace C89 and R91 with a new capacitor and a new resistor and you installed a 2 blade polarized cord,
    ensure you connect the cord's "AC Neutral" to the junction of C89, R91, and the power transformer's primary
    lead. With AC Neutral at C89/R91 and power transformer primary lead, you won't feel that AC tingle when
    touching the receiver's chassis. The polarized power cord can be plugged into your wall outlet only one way.

    The polarized power cord's "AC Neutral" wire is the one with "Ribs" along its length. If
    you're not sure, use your ohmmeter to test continuity from the "wide blade" and the
    stripped ends of the wires. The "ribbed" wire coating stripped end will show continuity
    with the wide blade.

    Mike W5RKL
    W2WJ likes this.
  3. N4KDF

    N4KDF Premium Subscriber QRZ Page

    I've located a true safety capacitor from a dead UPS. It's an Okaya PA104. I'll use that to replace the old cap in the radio. I've also got a polarized adapter permanently attached to the original line cord. Looks a little funky but avoids having to replace the original cord or hack of the existing plug. That would look bad and I'm trying to keep the radio unmolested. Installation of a fuse and switch in the primary circuit are my next obstacles. I really don't want to drill holes in the radio as it is in such nice condition.
  4. W9BRD

    W9BRD Ham Member QRZ Page

    The mains bypasses on my old Collins 32V-3 were bulkhead mounted and 0.1 uF as I recall. They passed enough current at 60 Hz to set up quite a bite.

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