Re: [Amps] Alpha 77dx L5 help

[Michael Tope <W4EF@dellroy.com>]

I just happen to stumble on this sentence when looking for reference 
information on Iron Powder cores: "Long term operation of iron powder 
cores above 80 °C can cause a permanent reduction in both Q and 
inductance." It seems to confirms your caution about trying to repair an 
iron powder core that has been overheated.
The sentence can be found near the bottom of page 5 in the application 
note "Iron Powder Cores for RF Applications" from Micrometals:
https://s3.amazonaws.com/micrometals-production/filer_public/85/52/8552a1c8-03d8-41f3-949c-7e89dd74be12/iron_powder_cores_for_rf_applications_app_note.pdf

73, Mike W4EF.............

On 12/3/2024 5:04 AM, gudguyham--- via Amps wrote:
> If a virgin core is broken you can probably fix it as stated but if the core overheats 
> the properties of the permeability often change and new cores are needed.  The 
> Command Technology HF2500 uses a similar toroid system and the cores are probably the 
> same.  Keep the burned one intact so you can count turns and where the taps go.
>
>
> Sent from the all new AOL app for iOS
>
>
> On Monday, December 2, 2024, 11:45 PM, Ron W4BIN <ka4inm@gmail.com> wrote:
>
>     Mr. Greg K1YW wrote:
>
> > I have a friend in Thailand who recently zorched out L5 in his 77DX.
> > Believe it or not, a small lizard got into the tank circuit and when
> > he was tuning on 80 meters, L5 got extremely hot - to the point of
> > cracking both of the torroidal cores! Does anyone know what specific
> > cores were used or if not, what the approximate value of inductance
> > that L5 should be? I assume these are iron powder cores. I'm trying to
> > help him remotely or perhaps send him a replacement
>     If they are broken in two (or more pieces) I have a friend that
> swears that after gluing broken
> powered iron cores back together they work just as good as new, after
> being epoxied back together,
> Clamp them together while the epoxy sets.  (a radiator hose band might do)

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