Icom 751a: No Transmit

Discussion in 'Radio Circuits, Repair & Performance' started by 88MAN, Jul 24, 2017.

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  1. 88MAN

    88MAN QRZ Member

    Well N8YX, I sent the 751a for restoration work an hour ago. It has hardly been used and doesn't have a scratch anywhere. I hope I get it back in the same esthetic condition... :)
     
  2. N8YX

    N8YX Ham Member QRZ Page

    Fingers crossed.

    One of mine is in like-new shape. The other...just needs a mint/NOS front panel and it'll look brand new. As it is, the rig just has the usual small wear marks around the panel edges but works FB.

    The R71As, on the other hand...need some VCO trimmer replacement and other attention. For what I paid for them, I didn't get hurt.
     
  3. KM4F

    KM4F Ham Member QRZ Page

    Who can you get to work on these on the SE part of the US?
    I have a 751 with a few issues, it's also been stored about 25 years:
    wobbly turning knob, probably just needs tightening, haven't looked into it
    missing one button (bottom right) I have no idea where it could by
    The main problem is on 10/12 meters, sometimes there is no transmit or receive. I can hear the relay clicks. Sometimes it works, sometimes not.

    I've been using a Kenwood 430 which is nice, but the 751 has FSK with I really can't do without during contests!

    I did have it cleaned up earlier pot-wise. It does work well otherwise.
    I just don't even have the time to pull it apart and check the relay and solder joints, you'd think without kids in the house you'd have more time, I seem to have less and less!
     
  4. W9GB

    W9GB Ham Member QRZ Page

    READ FIRST:
    eHam.net REVIEWS of Amateur Radio Equipment Repair (Shops & Individuals)
    http://www.eham.net/reviews/products/26

    Icom America : Authorized Dealer Service Centers (You obviously did not perform this step)
    Enter Zip Code. Select Amateur and Any Distance.
    http://www.icomamerica.com/en/support/partsandservice/servicecenters.aspx

    You will find that once a radio is dropped from factory support/service --- your options decrease.
    --
    The majority of highly qualified radio technicians specialize by radio brands (Icom, Yaesu, Kenwood); Equipment types (Transceivers, Amplifiers, HF, VHF/UHF, Microwaves, Rotators); or specific models (Yaesu FL-7000, FT-100MP; Kenwood TS-430/440; etc.)

    --
    For Icom, the three known are: SARTS (SW Michigan); MTS (Washington state); and Amateur Radio Service (Paul Hansen, W6XA -- former Icom SE Service).

    You will need to contact Paul -- while he returned to Georgia, unknown if accepting work.
    http://www.amateurradioservice.com/about.htm

    SARTS is now an Icom Midwest service center, BUT may accept your IC-751 for repair.
    http://www.sarts1.com/

    Scott Malcom (MTS) is best known tech for Icom radios from the 1970s and 1980s,
    largely due to his parts supply and donors sent to him (some parts unobtainium).
    http://mts-icom.wixsite.com/hamradiorepair

    Bill Graasa, N4ATS in St. Cloud, FL ... MAY be able to help (CALL First).
    While Bill specializes in Yaesu, he may look at your radio.
    http://www.n4ats.com/
     
    Last edited: Aug 2, 2017
  5. 88MAN

    88MAN QRZ Member

    The Icom 751a has been resurrected! Scott Malcolm (MTS) repaired the "no transmit" issue. It was a bad solder joint at the T9 regulator. I had him change electrolytic caps in key areas. Also, the plaster trimmer caps were replaced with ceramic ones. He does excellent work. The radio looks mint as it did before. Even though I got a Yaesu Ft-991a, nothing beats having real controls to every function on the radio. Not to mention the multi-function meter.
    Hopefully, I'll be OK for a few years. 2017-08-02 07.40.05.jpg
     
  6. W9GB

    W9GB Ham Member QRZ Page

    The Icom IC-751A is a nice HF radio from 1980s ... competitor to Kenwood TS-440S.
    IMG_4520.JPG
    SEE that 24-pin Molex connector on the Rear Panel, Upper Right?
    ACQUIRE that Molex 24-pin Nylon housing for the mating plug ASAP.
    http://www.mouser.com/ds/2/276/0003062241_CRIMP_HOUSINGS-133220.pdf
    BUY NOW (prices are rising).
    Why? Koch Industries purchased Molex in 2013.
    They are discontinuing 1970s/1980s connector housings with a large number of pins (>20).

    The Nylon molding for .062" Series : 24-pins are Marked for Obsolescence
    http://www.molex.com/molex/products/datasheet.jsp?part=active/0003062241_CRIMP_HOUSINGS.xml
    BUT the Pins/Sockets are still current production for lower pin moldings.

    MOUSER shows in Catalog --
    http://www.mouser.com/catalog/645/usd/1620.pdf
    BUT product page for Molex 03-06-2241 (24-pin mating connector) shows OBSOLETE.
    http://www.mouser.com/ProductDetail/Molex/03-06-2241/?qs=4l18HjQZIn8vDD2Y23XvZw==

    Rare "Retail" Peg board package.
    IMG_4521.JPG
     
    Last edited: Aug 26, 2017
  7. 88MAN

    88MAN QRZ Member

    Thanks W9GB for the handy information. It's already showing "not available" at Mouser. Wow!
     
  8. SP9O

    SP9O Ham Member QRZ Page

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