Yaesu FT-736 battery goop

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC3MBK, Sep 26, 2021.

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  1. KC3MBK

    KC3MBK Ham Member QRZ Page

    I'm replacing the battery on a Yaesu FT-736. Unsoldering was the easy part. This battery has this very hard, white goop holding it to the circuit board. Initially I thought it was just a white silicone. But it is as hard as a rock and is acting like a glue.

    Anyone know how to soften this stuff up?

    I don't want to try acetone for fear that it will damage to other stuff.

    Do you think a heat gun might soften it, as if it were a hot glue?

    Strange why they would do this on a replaceable part.

    Battery (Small).JPG
  2. KB2SUJ

    KB2SUJ Ham Member QRZ Page

    Epoxy potting. Intended to 'stabilize' the part and thence the board traces. I'd of clipped off at the battery and soldered in a cell holder to then make future battery replacements a breeze.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    My FT-736R, which I bought new in 1987 and have changed the battery twice now, did not have any of that goop.

    If you bought your rig used, I suspect a previous owner did that...it was not "factory done," at least not in mine and the two others I've worked on over the past 34 years.

    Be really careful. The holes are plated-through and I found applying soldering heat from the "back side" of the board (not the component side shown in your photo) works okay to remove the old battery, then clear any solder from the hole using a small-tip soldering pencil and a bit of "solder wick" clears out the holes. Too much heat can loosen the circuit traces and then you have a real repair on your hands.

    Although I haven't had to work with the "white goop" shown, I'd guess applying soldering heat from the back side of the board sufficient to melt the solder through the holes might loosen the goop also. Maybe not, but that's what I'd try, first.

    Thankfully Yaesu made the battery pretty easy to access once you remove the covers and drop the front panel down. Only a few screws holding the board in place and they're easy to get to. Don't forget to unplug the speaker wire, and also plug it back in when you install the top cover again.:)
  4. KC3MBK

    KC3MBK Ham Member QRZ Page

    Yea, already removed the solder before I took that picture. I have one of those powered solder sucker guns.

    I may try a heat gun on the white epoxy just to see if it softens. Certainly makes the job much more difficult than it needs to be.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You're fortunate the solder sucker didn't pull the foil right off the board. It's not wide and it's not well adhered.

    That's why I used "solder wick" instead. My solder suckers are a bit too powerful for work on thin traces.

    In any case, did you buy the rig used, and do you know the previous owner if so? Might ask him if he replaced the battery, and if so, what the "stuff" is.
  6. KC3MBK

    KC3MBK Ham Member QRZ Page

    I did buy it used. Previous owner was a member of our Ham Club. But he became a silent key a couple of years ago. His Wife finally decided to liquidate all of his ham gear, including antennas. It was a pretty large collection and me and another guy handled selling everything. But there were a few things that I wanted for my collection, and the Yaesu 736R was one. It has one extra module installed for 220 MHz, no 6 meters. It does have the optional CTCSS module. For the past couple of years it was stored in a plastic RubberMaid box in an outdoor shed. There is just the slightest trace of surface rust on the chassis, otherwise it is pristine.

    I do use solder wick on most things. My Prokit SS-331 is a new acquisition (pistol type desoldering tool).
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Sorry to hear about your club member friend.

    Since the 736R has been around for 34 years, it's likely the original owner replaced the memory battery so you're likely replacing it for the second time.

    The original one lasts 10-12 years, but not forever.

    Of course, the rig works fine without the battery but loses all memories. When my battery died, I didn't even know it because I never shut off the rig! As long as the rig is powered "on," it doesn't need the battery and all memories will be retained...until you shut it off!

    My 736R has been "off" maybe ten or twelve times in its 34-year life. Once plugged in "at home" I just leave it on all the time, with the lamp switch in "DIM" to preserve the meter lamps (and also the display, which also dims).
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    Glue can become a problem over the years.

    Cleaning bad glue from a PCB fixed a lot of problems. Flux Too.

    That glue just reduces stress on the solder connections due to vibration. Protects when the radio is dropped during shipping. :oops:
  9. KC3MBK

    KC3MBK Ham Member QRZ Page

    Goop is GONE!

    I broke the spot welds on the straps attached to the battery in order to get the battery out of the way.

    Then I broke out the heat gun. The white epoxy like stuff softened and I was able to pry it off the board and the straps remaining from the battery. Then removing the remaining straps was easy.

    I'm not sure why this was done. Unless you are hanging the 736 under the dash of a dump truck, I can't think of why this would be necessary.

    I really wanted the original mounting technique as I already have the replacement battery.

    Thanks to all that replied,


    GoopAway (Small).JPG
    K8BB, KA9JLM, KB2SUJ and 2 others like this.
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page


    Good job.

    Now to find out you installed the battery backwards...:p

    Only kidding. Good luck with the rig!

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