Realistic DX-300 bad LED display

Discussion in '"Boat Anchor" & Classic Equipment' started by KJ6ZOL, Nov 10, 2019 at 5:04 PM.

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  1. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    I wasn't sure where to post this, since this is a 1970s rig, so mods may move this post if needed.

    I got a Realistic DX-300 for $30 at the Valley of the Moon hamfest in Sonoma, Cal., earlier this year. The seller warned me it was untested, but I figured that $30 was still a good price considering what these go for on Ebay. I had no time for it then, so it went into the closet. So, this morning I finally fired it up, and the LED frequency display has a weird problem. It will only display numbers up to "999 khz" and then blink off. The rest of the circuitry seems fine, and I was tuning in Chinese domestic stns with no problem, but the display isn't working. Has anybody had the same problem with the DX-300 and fixed it?

    BTW, when you search for "Realistic radio" on Ebay, make sure you don't accidentally hit the first autocorrect entry for "realistic sex doll". :eek::eek::eek::eek:
     
  2. KF5FEI

    KF5FEI Ham Member QRZ Page

  3. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    That "Scribd" site wants an $8.99/mo autorenewed fee! :eek: Do you have any other sources?
     
  4. WA0YDE

    WA0YDE Ham Member QRZ Page

    Manualslib.com has it.....for free.
     
    KJ6ZOL likes this.
  5. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    Thanks. Looks like the Mhz part of the display is a different circuit than the khz part; it has something to do with a mechanical linkage while khz runs through an IC. Also, there seems to be a jumper involved. It's possible the jumper is missing, or the linkage is disconnected. I have a lot on my plate right now, so back in the closet it goes. :(
     
  6. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    That makes sense - the MHz is a simple switch sensing arrangement while the KHz is actually from a frequency counting circuit

    But without a schematic to look at, there's no way to guess things deeper than that.

    Note that the DX-300 was a pretty dreadful receiver - more "birdies" than actual signals. The DX-302 was a vast improvement - still not a great receiver but better performing than the 300.

    Dave
    W7UUU
     
  7. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    Dave, my primary intent in buying the 300 was to work "full duplex", where I could hear myself and any other stations trying to QSO at the same time. The tx/rx relay arrangement in HF transceivers has always bugged me. I will try to answer a CQ and when I click the PTT button off I will hear several other stns trying to do the same thing. I love trying to QSO special event and DXpedition stns, so obviously I want to choose the best opening to be heard. Most of the GRE manufactured Radio Shack rigs were pretty chintzy as far as circuitry went, they were built for the low end of the market at a time when inflation was raging and people didn't have a lot of money laying around. People wanted a relatively nice SW rx without having to venture into a radio store catering to hams. RS filled a need in the market in their heyday, that's for sure.
     
  8. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    I will say the AX-190 (ham bands only) and SX-190 receivers made by GRE (I always thought they were Trio/Kenwood!) were the very best of the offerings from Radio Shack in that era. I used an AX-190 I bought used in 1980 for about 3 years as my sole CW receiver and worked the world. Of course, it was during a very good solar period - but I was always pleased with how the AX-190 performed. At the same time I also had a DX-302 that despite having the cool digital display, was pretty inferior to the analog AX-190.

    Good luck in solving your problem - don't give up until you have a decent-resolution schematic in hand to help diagnose what's going on.

    Dave
    W7UUU
     
  9. KF5FEI

    KF5FEI Ham Member QRZ Page

    Really? You couldn't find squat, and then you gripe because someone does the work for you, but it's a pay site? They had a 30-day free thing, which I did not explore, because I didn't need the manual.
     
  10. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I have both the DX-300 owner's manual and the DX-300 service manual in PDF files.

    Contact me, by E-Mail, at the following E-Mail address:

    k9sth (at) sbcglobal (dot) net

    and I can attach the files to my return E-Mail.

    Glen, K9STH
     
    W7UUU likes this.

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