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
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
