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Yaesu FT-8100R wont turn on

Discussion in 'Radio Circuits, Repair & Performance' started by KB1THM, Dec 24, 2019.

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  1. KB1THM

    KB1THM Ham Member QRZ Page

    I have a question about my yaesu ft-8100r 2/440 radio. I just took it out of storage, it has been about a year or so since I last turned it on, and before I was having no issues with it. I try to power up and nothing. Checked the fuses and the zener diode across the circut board where the power comes in and everything checks out. Even right where the wires are soldered to the board there is 13.5 volts. Looking at the circut board you can see a previous repair where there is a jumper wire installed across a burned trace. I think that is a common issue with this radio, but I dont think that would be an issue that would arise after being in storage. Also a previous owner did a mars/ cap mod. It was in a cold attic for a year and heat as well. Any ideas or is this radio junk? I have basic electronics skills and basic soldering capabilities, I am no expert. I could not see anything out of the ordinary here.

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  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Did you check the connectors that connect the radio to the control head ?

    You may just need to clean those connections.

    Good Luck.
     
  3. KD0RCB

    KD0RCB Ham Member QRZ Page

    What I would try is to remove the top and bottom covers , apply power, and heat the pc boards, slowly on both sides, with a hairdryer, in all areas, esp around the electrolytic caps, and keep trying to turn the radio on as you do this..... Capacitors, after sitting for a long time, especially in cold, will develop very high ESR. Many times I have seen this in various electronics, and they will test high - bad- with a good ESR meter. Heating can temporarily lower the internal resistance of the electrolyte , and begin to work again. If you find an area that is touchy and begins to work when heated, I would suggest replacing any caps in that area. Good luck, Randy.
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    I never do the shotgun method.

    The head of the radio needs to have a good connection before it will turn on.

    • Theft-Deterrent Detachable Front Panel
    If the radio needs to be warmed up, I put it in the oven. :D (Light on Only)
     
    Last edited: Dec 24, 2019
  5. KB1THM

    KB1THM Ham Member QRZ Page

    Okay thank you. Let me give these methods a try and report back!
     
  6. KD0RCB

    KD0RCB Ham Member QRZ Page

    No, its not a shotgun method- its a quick , effective, and cheap way to narrow down a possible ESR cap issue...if heating various pinpoint areas don't seem to affect the problem, of course move on to deeper troubleshooting methods, for there are many. As far as putting the whole radio in an oven, that would heat the whole radio, and wouldn't help in pinpointing any specific area...The blowdryer method is a lot cheaper than spending hundreds of $$ on a quality ESR meter like I did, which they may never use again. Using heat (or cold) can be a very effective troubleshooting tool for diagnosing certain problems. Randy.
     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    I agree.

    I just do not like the idea of replacing caps that are OK, And do not need replacement.

    Many time the PCB can get damaged replacing parts that are just fine.
     

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