Date: Thu, 17 Jan 2019 12:14:30 +0000
From: Chris Wilson <dead.fets@gmail.com>
Message-ID: <1973353494.20190117121430@gmail.com>
To: N1BUG <rsgb_lf_group@blacksheep.org>
In-Reply-To: <92fbbb62-a1fe-0e0f-c048-08dd3c2cdfb2@n1bug.com>
References: <16856e12994.marcocadeddu@tin.it> <92fbbb62-a1fe-0e0f-c048-08dd3c2cdfb2@n1bug.com>
MIME-Version: 1.0
Subject: Re: R: RE: LF: JT9-10 vs JT9-5 test ends with smoke :)
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Hello N1BUG,

Personally I would machine or cut a piece of brass tube so the bolt
head, nut and washers, plus the connectors are tightened against the
brass tube, not the plastic. The tube can then just be a loose or push
fit into the plastic former.

Thursday, January 17, 2019, 12:01:19 PM, you wrote:

> Hi Marco,

> It's always interesting to see pics from other collections if you
> want to share. :-)

> After careful study of the ruined coil, I made a guess:

> SS hardware was a poor choice. Using the machine screw to carry RF
> from inside to outside of the coil form was not the best way. I
> think the hardware became slightly loose. We have all seen this
> happen when hardware is installed in "soft" plastics. Loose hardware
> caused higher resistance in the connection and more heat. More heat
> softened the plastic, which made the hardware more loose, more
> resistance, more heat. Eventually the connection became so loose
> there was an arc, too much heat and everything burned.

> Well, it's just a guess, but it's not too hard to imagine this can
> happen.

> Every nut and screw on that unit was a bit loose, even the ones that
> did not yet show any sign of overheating.

> I cut and drilled already a new coil form but I wait now for brass
> hardware to arrive before winding.

> 73,
> Paul


-- 
Best regards,
 Chris                            mailto:dead.fets@gmail.com