Hi Curt,
Thanks for your advice. I have copied the list in now as you suggest.
I do have Gary's excellent CD.
Regrettably I did not catch it in time. Great pity it was all tested out okay
all bands ready for an antenna!
73
Damien
Date: Thu, 13 Mar 2014 13:24:28 -0500
From: cptc...@flash.net
To: damienman...@hotmail.com; drakelist@zerobeat.net
Subject: Re: [Drakelist] What have I done now?
Hi Damien:
Yes, especially when replying to posts, be sure to note where the
reply is directed address-wise. Always good to copy the list as
well as any direct message so others can follow along with the
discussion responses.
The scenario Garey outlined is very likely indeed. It kind of was
an extension of my comment about it is sometimes hard to tell
exactly what was going to happen in all stages of the rig. He
went into the schematic a little deeper than I did--All of those
guys are very knowledgeable in the Drake line-up.
If you plan to do much work at all on these rigs, Garey's CD with
annotated pictures and notes is the best available as far as I
know.
Hopefully, you caught it before the finals or other parts got
damaged.
BTW, a fan pulling air out of the back of the cage is a great
benefit to these rigs to shed some of the heat. That being said,
these things will run 24/7 at rated output in tough modes like
RTTY and just keep going--they are very robust as long as properly
loaded.
Cheers
Curt
On 3/13/2014 11:20 AM, Damien Mannix wrote:
Hi Curt,
Thanks again. I will do everything you suggest.
Actually I am puzzled myself as to how the list works
nowadays! I did in fact also hear from Mike Bryce (no call
sign given), Evan K9SQG and Gary K4OAH who also kindly invited
me to join the DrakeRadio group. Never knew it existed but I
will certainly join.
Regards,
Damien G3XER
Date: Thu, 13 Mar 2014 11:07:11 -0500
From: cptc...@flash.net
To: damienman...@hotmail.com; drakelist@zerobeat.net
Subject: Re: [Drakelist] What have I done now?
Hi Damien:
Doesn't change my thoughts really. Even tho the relay for
Tx would not be engaged, and this keeps the cathodes
floating and not grounded, with bias very low or removed
from the grids, the tubes will conduct enough to get hot for
sure. I think the worst is that the current comes thru the
grids so can physically damage the tube internals.
Which tubes, finals or driver, or others, is a guess
only--perhaps all to some degree. I would just power it up
again with a full on AC4 and monitor it closely to be sure
nothing has gotten burned or out of tolerance enough to do
damage. Especially, confirm that the bias control does what
it is supposed to do with adjustment range, verify that the
current reading of plate current is close (be careful!) and
do an operational check-out.
These are very robust rigs but the finals are especially
intolerant of unloaded or excessive plate current being that
they are TV sweep tubes.
Let us know how it goes. Kind of surprised we haven't heard
from anyone else on the list.
Curt
KU8L
On 3/13/2014 10:31 AM, Damien Mannix wrote:
Hi Curt,
Thank you for your two replies. I am most grateful for
your input. How one can be misled. I certainly thought I
was doing the right thing!
No sure if it makes any difference to your conclusions
but I never switched to transmit I just left the TR4 in
Receive mode.
73
Damien
Date: Thu, 13 Mar 2014 08:25:26
-0500
From: cptc...@flash.net
To: drakelist@zerobeat.net
Subject: Re: [Drakelist] What have I done now?
Thinking about it a
little more, since it may or may not have transitioned
to TX, the driver or any of the other tubes that are
bias controlled can do the same at reduced voltages.
Hope there was no long term damage.
I once worked on a FT101E that had a defective socket
on the grid of one of the finals. As soon as HV came
on, with that grid floating, it began cooking. Bias
measured OK, all voltages lookedOK, but no bias was
getting to the actual tube--duh! I finally figured
out what was going on after the tube got so hot, the
vacuum sucked a hole thru the side of the tube. Still
have that tube BTW...reminder..
Curt
KU8L
On 3/12/2014 12:18 PM, Damien Mannix wrote:
Hi all,
Still waiting for better weather to put up an
antenna but then ready to go with my TR4/AC4 which
are fine into a dummy load, or at least they were!
Bought a, supposedly good, AC4 as a spare. Decided
to power it up gradually with the TR4 as a load.
Two hours at 50v, two at 80v, two at 110v, two at
140v. No problems and a fan on the rear behind the
PA begins to run at this voltage. Then, ten minutes
at 170v and 'wow' what is that smell? I thought it
was my shack heater.
No it was the TR4. The top, above the forward most
PA tube, was unbelievably hot. Switched off
immediately of course.
Can't spot anything untoward in the PA compartment
so after a complete cool down I took it slowly up to
230v with my usual AC4. Not done a full test but it
seems perfectly happy again, heat and smell wise,
after 30 minutes at 230v.
Might I have ruined anything and, presumably, the
fault is in the AC4.
Thanks in advance for any thoughts.
73
Damien G3XER
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