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Icom IC-910H low power

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• Icom IC-910H low power

• Icom IC-910H low power

  VK5PJ > 16-09-2016, 04:15 PM

  the start of this thread really starts here, so please have a read to get any needed background
  
  http://www.vklogger.com/forum/viewtopic....974#p61974
  
  So last night all the stars aligned, the new FET had arrived, I had been practicing with the hot air soldering station (elcheapo from ebay) so it was time to push back my aprehension and just DO IT.
  
  Cleaned up the PCB, freshened up the solder tining on the heatsink and the under side of the PCB and then put them together with some BIG heat. Now this is while they are still OUT of the 910.
  
  Have let it all cool down and checked that the pre-driver board is now attached the small heatsink.
  Tin the underside pads of the new FET
  
  *-Caution-* Exisiting capacitors and larger resistors on the board do start to become mobile with the hot air gun, so be careful where you point it
  
  Now time to get the assembly back up to temp by blowing air from the top on the exposed section of the heatsink that pokes through the board. check at intervals to see if it melts som fine solder (air gun removed) then once confident it is hot it is time to introduce the FET and keep the heat on while its pads take the solder from the PCB, I added a small amount of fine solder to ensure it was all flowing.
  
  Let it all cool down again.
  
  Put the board back into the 910, I used the hot air again to get each side of the board to slide down the header pins by waving it back and forth and a small amount of pressure from a fine tool.
  
  Put the securing screw back in to mate it all up to the main chasis and BEFORE you tighten it up, wave the hot air across the header pins to make sure it is all home, then tighten the screw, you can repeat this a few times if unsure.
  
  Okay, here is the reward, straight to 70cm on FM tx and there was 70W on the external power meter and it did not waver one little bit. At this point I stopped and went back to the house to calm my nerves, more extensive testing later.
  
  I have some photos I will contribute later on,
  
  Peter, vk5pj

• Re: Icom IC-910H low power

  VK5ZLR > 16-09-2016, 06:32 PM

  Good save.
  
  Now I can send all my fixups to Peter's Radio and TV repairs.

• Re: Icom IC-910H low power

  VK2KRR > 17-09-2016, 08:53 AM

  Excellent work Peter, let me know if u want to test it on 70cm WSPR I can go back over there, just on 2 at present. :ugeek:

• Re: Icom IC-910H low power

  VK5KK > 03-10-2016, 06:46 PM

  Hi All,
  
  Have updated the driver in Dad's IC910H to a RD07MVS-1B FET ... its had a fair flogging on WSPR over the last few years!
  I used teflon tape to protect the PCB components when using the blow torch (joking .. rework station)
  
     
  
  Final installation of new FET
  
     
  
  Cheers
  
  David VK5KK

• Re: Icom IC-910H low power

  VK5PJ > 03-10-2016, 06:50 PM

  Hi David,
  may I ask what changes you made to the BIAS circuit for that FET?

• Re: Icom IC-910H low power

  VK5KK > 07-10-2016, 07:31 PM

  Hi Peter,
  
  Checking the specs it needs about the same +2.5V on the gate as the original but that is at 7.2V VDs. I haven't set the bias yet, with the FET out the range was 2 to 3 volts over R131's full range. It's now on the test bench so will post the results over the weekend! BTW the old MosFET showed a fair amount of temperature drift
  
  Cheers
  
  David VK5KK
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