757 GX2

Discussion in 'Radio Circuits, Repair & Performance' started by N4DXX, Jun 1, 2019.

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  1. N4DXX

    N4DXX Ham Member QRZ Page

    This radio was working fine and i rmoved the top cover to replace a blown light in the meter..well put it back together and the radio comes on but only the tx light and the meter pegs..No display no sound nothing just a red tx light and pegging meter..Cant find anything loose and the voltages all seem ok on the pa unit ..relay is activating when the power button is pressed..Help!
     
  2. N3DT

    N3DT Ham Member QRZ Page

    Undoubtedly some connector is loose. Check it carefully and re-seat any you messed with and maybe any you didn't.
     
    G4COE likes this.
  3. G4COE

    G4COE Ham Member QRZ Page

    Agree with N3DT.

    Ribbon cables are notorious, they look smugly in and yet they are not....be very careful with these, you pull em' out straight and put them in straight because if you bend the ends there is every chance the fine silver foil contacts will part from the plastic base.... and you'll have a very hard time in inserting it with a possibility of it bending across the others and creating a short.

    The crimp connections can also be problematic, the wire's may have become loose or parted from the crimp so this is another thing to look out for.

    Dave
     
  4. N4DXX

    N4DXX Ham Member QRZ Page

    Ok,I have it powered up and has good rx..Loose connection..Now i have another issue..I have good rf drive going into the pa board and have tested the 1971 pre driver the drivers and finals..All test good using a atlas dca 55 tester..Can not get any output and can't get my bias setting to go over 10 MA or so no where near the 250ma the service manual calls for..will this low bias cause No rf output?Also has good signal and audio into a nearby receiver..Thanks
     
  5. N4DXX

    N4DXX Ham Member QRZ Page

    Fixed had shorted cap in pa unit..old age i guess..Thanks
     
  6. G4COE

    G4COE Ham Member QRZ Page

    Good work
     

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