[Heathkit] HW-8 and HW-7 toroids?

[Garey Barrell]

Tom -

I have seen several references to this problem in the HW toroids.   I was
designing / building 50W transmitters in the 450 MHz region back in the mid
60's.   We ran into a similar problem whenever I managed to vaporize a
transistor in an untamed amplifier, and determined that the strong DC
current pulse was actually magnetizing the toroidal core and drastically
altering it's permeability.   Rather than wind another toroid, I found that
demagnetizing it (by passing it through a "demagnetizer" [read Weller
soldering gun] loop) returned it to "normal".

It would be interesting to try demagnetizing one or more of these HW toroids
to see if that would "fix" it.   Or has this already been tried?

By the way, I also discovered that you can actually "see" the flash through
the ceramic top of those transistors!  :-)

73, Garey - K4OAH
Atlanta

----- Original Message ----- 
From: "Tom N�JMY - AAR7FV" <tfarl@mchsi.com>

> Question for the QRP guys.  I have an acquaintance who is in the pre-wound
> toroid business.  I have him contemplating offering the problematical
> 4-toroid HW-8 output set for 80 and 40 meters.  So far, every HW-8 I've
> encountered needed new ones to get back up to rated output, due to
> permeability changes.  Granted, I've only encountered three, hi hi.
>
> My question is this: does the HW-7 also use the same parts?  I was
thinking
> I was told that the HW-9 did not, but that the HW-7 did.
>
> Can someone clear me up on this one?
>
> Tnx es vy 73,
> Tom
>