Icom 735,delay in receive after finished transmitting..

Discussion in 'Radio Circuits, Repair & Performance' started by VE1ELK, Nov 14, 2017 at 1:29 AM.

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  1. VE1ELK

    VE1ELK Ham Member QRZ Page

    Hello to all,i hope this has been seen by others in the past..it just started happening..transmit awhile and the receive does not come back right away 100%,i used to hit the ptt button on the sm 8 and it would kick something back into place..whatever that is..not it wants to not do it and i have to let the radio sit there and a few minutes it will come back 100%,it makes me think theres band filter relays or something like that,that has dirty contacts..and quick flicks cleared it but it has gotten worser...so anyway just wondering if this has happened to anyone else...and is there coil relays in there..i am downloading the schematics as I type and i hate to yank a radio all apart unless i know right where to go..I do have a rtl sdr to make up the receive but heck..i have to have pc runnin then.i hope its a easy fix and it will be if its a relay..old school electronics is in my back yard. Thanks
     
  2. AF7XT

    AF7XT Ham Member QRZ Page

    if not dirty relay then just the dumb question. VOX much ?
     
  3. N8VIL

    N8VIL Ham Member QRZ Page

    Check the relay. Mine did that many years ago and it was the relay towards the back on the PCB by the input bandpass filter section. I replaced it and all was fine.
     
  4. N8VIL

    N8VIL Ham Member QRZ Page

    ic735board.jpg
    Here is a picture of the board with the relay. Take the bottom cover off. Transmit for a second and tap on the relay and see if the receive comes right back. That will verify if this relay is the suspect. I believe it to be the attenuation switching relay now that I come to think of it. There is also a relay in the PA module that may be bad also. The PA boards were known to have bad connections that connect to the antenna connectors.
     
    Last edited: Nov 14, 2017 at 2:26 AM
  5. VE1IC

    VE1IC Ham Member QRZ Page

    very good chance on the rx/tx relay. However, it really depends on how the rx comes back. Does it come back right away, but it is attenuated, or does it come back with no receive? To check if it is the band filter relays, simply switch to a different band and see if the problem occurs there too. Usually around here it's the 80m band relays that go bad, if it is them. Doesn't matter if they are sealed or not, I've replaced even the sealed once before too.
     

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