From: [email protected] (Warren K2ORS/WD2XGJ)
Reply-To: [email protected]
To: [email protected]
Subject: Re: LF: Re: Keeping the smoke in
Date: Thu, 02 Feb 2006 23:10:18 +0000
Hi Mike,
I don't think that the cores were damaged from the last incident. I was
able to run the 250 watt transmitter through it with no problem and no
measureable reflected power. I understand that Laurence also used 3 stacked
FT-290-77s but actively cooled it. A cooling fan is not easy to do in my
case since the tuner is in a weathertight box.
--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm
-------------- Original message ----------------------
From: "MIKE REID" <[email protected]>
> What cores did Laurence use and what wire size & type? Sorry to hear she
failed
> again. Maybe the cores got damaged the other day with no external
indications
> like cracking or? I don't recall you having trouble with the transformer
when it
> was dry and Teflon is way better than cotton so that leads me to think
the cores
> were no good after the first heat cycle/failure.
>
> Mike
> WE0H
>
> ----- Original Message -----
> From: Warren K2ORS/WD2XGJ
> To: rsgb lf reflector<mailto:[email protected]>
> Cc: LWCA LF Reflector<mailto:[email protected]>
> Sent: Thursday, February 02, 2006 4:41 PM
> Subject: LF: Keeping the smoke in
>
>
> Hello the list,
>
> I've heard that the secret to keeping things going in
electronics is to
> make sure you don't let the smoke out (that's what makes it all work
> apparently).
>
> I have again failed to do so. After rewinding my toroidal loop
> transformer in the ATU, I had a core overheating problem. The core is 3
stacked
> FT-290-77 ferrites.
> After setting the Decca up on QRSS for an hour or so I noticed a
problem with
> the rf output current, it was pulsing up and down as if the Decca guard
circuit
> was cutting in to protect the PA. So I through the breaker and went out
and
> opened the tuner box. Smoke poured out. Bad news. I checked the
temperatures
> with a non-contact infra-red thermometer and the toroid core was 343
Farenheit.
> The Curie temperature for type 77 ferrite is 200 C (which is 392
Farenheit).
> Not sure yet if the core is permanently damaged, I'm still waiting for
it to
> cool down.
>
> All credit to Laurence who managed to get a loop to work at this
power
> level! And especially with the currents he dealt with in the parallel
wire loop
> configuration.
>
> I guess I need a bigger core than the 3 stacked FT-290-77s any
suggestions
> out there?
>
> --
> 73 Warren K2ORS/WD2XGJ
> FN42hi
> http://www.w4dex.com/wd2xgj.htm<http://www.w4dex.com/wd2xgj.htm>
>
>
