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Yaesu FT-897 Very low output power

Discussion in 'Ham Equipment' started by br9613, May 21, 2011.

  1. br9613

    br9613 Member

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    Turned the radio on the other day and noticed I had very little output power accross all bands, The radio is only pulling around 1.7 amps in FM transmit mode, should be in the neighborhood of 20. Before I send it in for a look I was wondering if anyone had any ideas I could try. I have done a full blown reset and it didnt help. All other aspects seem fine. Allfuctions operate and it receives fine jus very little power. Also used a dummy load and meter and it doesnt even move the needle so I checked the overall currernt draw and it ranges from 1.7 to 1.5. I would think maybe the final are bad but would that occur in all modes, HF,UHF and VHF. Anyway thanks for any help in advance.


     

  2. Radioman1

    Radioman1 W9WDX Amateur Radio Club Member

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    Low power 897

    Before I sent it back I would swap the coax jumpers

    used in your test for some other ones and verify that

    it was in fact my radio, possibly carry to another

    Ham's shack and ask him to check it out on his

    equipment, it's happened before.....Mac
     
  3. HiDef

    HiDef Active Member

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    Here's an interesting collection of stuff from a trusted source. It may not help but anyone with one of these radios should have a look:

    FT897 IDLING CURRENT ADJUSTMENT
     
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Does it have good power output on SSB on HF? If it does it is not the finals. Does it have good power output in FM mode on VHF or UHF? There is a separate power output module for V/UHF.
     
  5. br9613

    br9613 Member

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    Low output

    No it has no power throughout all bands and modes. I m pretty sure it is the finals. Is anyone familiar with the procedure for replacing or is it just easier to send in and have it done. I know on older units it is something that can be done but im not sure about this model. Thanks
     
  6. br9613

    br9613 Member

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    Low output

    Took a look inside and dont see anything that looks like a problem butI know that doesn mean much on these newer units. Other than the finals what would cause this problem on all bands and modes, If the finals were bad would the radio still not draw the normal current. All it is pulling is around 1.7 amps on transmit and about 1 on receive. Im just wondering what could go out before the finals that would affect all output. Ive seen some mention of a cat fuse but not sure if this has anything to do with my problem

    Thanks again for all the help;
     
  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    If it has no power out on ALL bands and ALL modes including the VHF and UHF bands it is NOT the finals. There is a completely separate output module and circuitry for those bands regardless of mode. The chances of loosing all the finals for all bands is pretty remote unless it was struck by lightning.


    Is the power supply good? What is the voltage while transmitting?
     
  8. br9613

    br9613 Member

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    low output

    The voltage is at 13.7, it dips a little when I push transmit to 13.6, This is on the display, I double checked my power supply and it is accurate. It puts out a signal that my handheld can pick up but it wont even register on the SWR or power meter. The display doesnt show anything on the power meter when depressed. I am using a 25 amp power supply which should be adequate. I tried running it through a linear amp I had and it doesnt even trigger the amp when transmit is pressed, Like I said there is a signal I can pick up on my handheld when Im within about 100ft of the unit but thats about it. Ive tried all bands and same thing. Im thinking the same thing that it would be almost omposible to lose all of the finals. I know there was no surge or lightning involeved. Perhaps a CPU issue, I have noticed some irregularities with my FM repeater shift, sometimes it doesnt shift and then it does, I havent ruled out human error on that one though. Im still learning some things on this radio.
    I double checked the service menu and its all in line as it should. Just very weak output. One question, Since the radio isnt drawing any amps when transmitting , does that point to anything else other than finals.
     
  9. KE5MC

    KE5MC Guest

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    Internal power distribution

    An earlier post pointed out possible power issues. I would have to go back to read the post again if the intent was external or internal. If you have access to a schematic check the internal power and see if there is a voltage that is common to the driver/power amp stages for the various bands. There might be other means to explain your symptoms, but a common voltage is one. It can be surprising how incoming power is changed and distributed to run all the functions in todays radios

    Good Luck!


     
  10. Happy_Hamer

    Happy_Hamer Administrator
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    Is this the D model?
     
  11. br9613

    br9613 Member

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    No, its the non D model. I do have a schematic and I was looking for the same thing, However there are numerous sources that poer all bands and it doesnt give me the details on what the correct readings should be. I saw mention of a chip fuse on another site but I dont believe the other function would be functional if it was blown. The receiver seems fine it pulls in strong just no output,Im attaching the schematic and service manual if anyone needs or wants it. It does show 3 finals. It goes through one then splits off and goes inro 1 for UHF/VHF and another for 50mhz. Im going to see if Im gettin anything to the first one it shows 13.6 volts. Before it is a Pre Drive at 5Volts . Anyway Thnaks again, Im just going to start backtracking with the schematic and see,, Page 5 is wher Im looking.
     
  12. Brlux

    Brlux Member

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    I have an 857 (nearly electrically identical to the 897) that does something similar,mine has no power on CW across all bands but is fine with other modes.

    I have a friend who had a problem that sounded almost exactly like yours on his 857. No out power all bands all modes. It just happened over night for no reason. He sent it in to Yaesu and a little under $100 later they ended up replacing 6-7 diodes.
     
  13. br9613

    br9613 Member

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    thanks for all the replys, I will be sending off today and will post the results,
     
  14. Happy_Hamer

    Happy_Hamer Administrator
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    Any info yet?
     
  15. F1RAF

    F1RAF Member

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    I guess that you have blown one of the driver FET on the main unit. Check for Q1006 or Q1007 if they are burnt...
    I had that issue, with similar finding less than 2A, few milliwatts output, all modes, all bands... and just ordered for a 2SK2973 transistor...

    Regards, Nicolas F1RAF


     

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