Re: R: RE: LF: JT9-10 vs JT9-5 test ends with smoke :)

[N1BUG <paul@n1bug.com>]

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



On 1/16/19 8:37 AM, marcocadeddu@tin.it wrote:
> ;-) I agree and will support you with the new meaning for LF!!
> 
> Paul, the new pic is more impressive and shows a big burn... I
> could send you some pic from my collection ;-) Just an idea for
> the new version you are planning. As far as I understood the
> mobile coil is part of the loading coil (If I assume wrong
> discard..) where is it placed? would suggest to place in the
> bottom part of the coil just to be in the lower voltage
> environment.
> 
> Of course when RF want to burn .. it burns!
> 
> Marco, IK1HSS
> 
> 
> 
> ----Messaggio originale---- Da: luis@vigilant.es Data:
> 16-gen-2019 10.25 A:
> "rsgb_lf_group@blacksheep.org"<rsgb_lf_group@blacksheep.org> Ogg:
> RE: LF: JT9-10 vs JT9-5 test ends with smoke :)
> 
> Sorry to see the damages Paul. As Chris said very certainly "LF
> without smoke is QRP" ;-)
> 
> I would add that LF stands for "Let's Fire" and a "!" should be
> added at the end
> 
> 73 de Luis EA5DOM
> 
> -----Mensaje original----- De: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de N1BUG 
> Enviado el: martes, 15 de enero de 2019 22:56 Para:
> rsgb_lf_group@blacksheep.org Asunto: Re: LF: JT9-10 vs JT9-5 test
> ends with smoke :)
> 
> Eventually I will rebuild it perfect... although I would prefer
> to start over with a new coil as this one requires too much
> maintenance. Right now I don't have the luxury of time for any of
> that. It's solar minimum and I need this thing working. :)
> 
> I don't trust the inner coil form for HV now, too much carbon:
> 
> http://www.n1bug.com/vario-fail-2-1200.jpg
> 
> So that'll have to get replaced. I will make the connections
> differently this time!
> 
> 73, Paul
> 
> 
> 
> On 1/15/19 10:42 AM, Chris Wilson wrote:
>> 
>> 
>> Hello N1BUG,
>> 
>> I  too  have had issues with bolted connections to the
>> variometer. Not an  expensive  fix  so  long as you don't mind
>> a few battle scars, but knowing  you,  you  probably  want it
>> cosmetically perfect again ;) LF without smoke is QRP...
>> 
>> Tuesday, January 15, 2019, 2:50:18 PM, you wrote:
>> 
>>> Thanks to all who monitored and provided reports on this
>>> latest test of slow JT9 modes.
>> 
>>> The test ended suddenly around dawn this morning. Here is the
>>> reason:
>> 
>>> http://www.n1bug.com/vario-fail-1-1200.jpg
>> 
>>> It's the inner coil from the 2200m loading coil /
>>> variometer:
>> 
>>> http://www.n1bug.com/vario-fail-0-1200.jpg
>> 
>>> I had hoped to be on looking for QSOs tonight, but obviously
>>> that is not going to be possible. I do not know when I will
>>> be QRV again.
>> 
>>> I have a very busy day today, so the final report on the JT9
>>> test might not be ready until tomorrow.
>> 
>>> 73, Paul N1BUG