HTML Image
Forum: 1 Lucky Nerd

  1. Forum
  2. FidoNet
  3. AMATEUR RADIO

  • Removing resin from a 49:1 sealed transformer

    From bgonev@2:240/8001 to All on Wednesday, June 18, 2025 21:01:14
    Hi All,

    After I do not know how many years, I'm back here on the net :).
    So back to the primary topic:
    Recently I've purchased an 49:1 unun from a manufacturer, but I am not satisfied with the performance of it (compared with another 49:1 transformer the SWR is notably higher.
    Therefore I plan to dissassemble it completely, but the main problem is that the ferrite inside the box is sealed wit a resin. I would like to hear your opinions or experience, how to safely remove the resin without damaging/destroying the ferrite ?

    Thank you
    73 de Z32X

    --- Mystic BBS v1.12 A43 2019/03/03 (Windows/32)
    * Origin: BlackICE BBS (BlackICE.BBSindex.com:23) (2:240/8001)
  • From Scott Street@1:266/625 to bgonev on Wednesday, June 18, 2025 18:15:24

    Therefore I plan to dissassemble it completely, but the main problem is that the ferrite inside the box is sealed wit a resin. I would like to hear your opinions or experience, how to safely remove the resin without damaging/destroying the ferrite ?

    I would use heat from a heat gun to soften the resin and pick it out with fine tools. In my experience, their just isn't a really good way, fast way. Do a little area at a time with minimal heat to avoid cooking the resin and causing a bigger mess.

    Best of luck!

    --- Mystic BBS v1.12 A49 2024/05/29 (Linux/64)
    * Origin: <=-{ The Digital Post }-=> (1:266/625)
  • From bgonev@2:240/8001 to Scott Street on Sunday, June 29, 2025 16:20:09
    Tnx Scott,

    I've managed to remove the resin, and now the toroid can be reused for
    another project. The way how I've removed was a 3-hour-lasting process of boiling the block into a boiling water, and chipping out parts of the resin
    in the first 10 seconds after the block was out of the water. After 10
    seconds the resin was solidifying so, it was a repetitive process of
    boil+chip out... You were right, not an easy way to remove it..

    BR,
    Boris

    --- Mystic BBS v1.12 A43 2019/03/03 (Windows/32)
    * Origin: BlackICE BBS (BlackICE.BBSindex.com:23) (2:240/8001)
  • From Mortar M.@1:124/5016 to bgonev on Sunday, June 29, 2025 12:41:40
    Re: Re: Removing resin from a 49:1 sealed transformer
    By: bgonev to Scott Street on Sun Jun 29 2025 16:20:09

    The way [I did it] was a [3-hour] process of [submerging] the block [in] boiling water, and chipping out parts of the resin...

    Wouldn't that damage the components inside?
    --- SBBSecho 3.28-Linux
    * Origin: End Of The Line BBS - endofthelinebbs.com (1:124/5016)
  • From bgonev@2:240/8001 to Mortar M. on Sunday, June 29, 2025 21:48:36
    Well, the main aim was to salvage/save the toroid, not the windings. Also the female PL259 connector was saved..

    73 de Z32X

    --- Mystic BBS v1.12 A43 2019/03/03 (Windows/32)
    * Origin: BlackICE BBS (BlackICE.BBSindex.com:23) (2:240/8001)
  • From Scott Street@1:266/625 to bgonev on Monday, June 30, 2025 06:11:58
    On 29 Jun 2025, bgonev said the following...
    Tnx Scott,

    You are welcome.

    I've managed to remove the resin, and now the toroid can be reused for another project. The way how I've removed was a 3-hour-lasting process of boiling the block into a boiling water, and chipping out parts of the resin in the first 10 seconds after the block was out of the water.
    After 10 seconds the resin was solidifying so, it was a repetitive
    process of boil+chip out... You were right, not an easy way to remove
    it..

    I know manufacturers add the resin (potting) to stabilize components for vibration resistance, but holy cow does it make it hard to repair a minor fault in such devices. My best examples are automatic voltage regulators from portable generators, in many cases the capacitor will fail, maybe the bridge rectifier might be bad on one side... but it is the same hours of heating, picking, and swearing. :)

    Glad you got the part you needed, I just hope it works after all that.

    Good luck!

    --- Mystic BBS v1.12 A49 2024/05/29 (Linux/64)
    * Origin: <=-{ The Digital Post }-=> (1:266/625)
  • From bgonev@2:240/8001 to Scott Street on Tuesday, July 01, 2025 14:00:04
    Well, not that the core is out and free, I will use today to create 4:1
    Balun. I am thinking to build 2 core Guanella version (not stacked), which in essence is a design based on two interconnected 1:1 Baluns. I've read on the net that this design is the "real" 4:1 Balun, compared to the single core design which does not provide stable balance to unbalance transformation, and that it is possible to provide the common current to the shield of the
    coaxial feed line.
    I will appreciate if someone have comparison experience based on usage on
    these 2 different designs..

    73,
    Z32X

    --- Mystic BBS v1.12 A43 2019/03/03 (Windows/32)
    * Origin: BlackICE BBS (BlackICE.BBSindex.com:23) (2:240/8001)

I recommend using



to connect to the BBS