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 <mailto:cptc...@flash.net>
To: drakelist@zerobeat.net <mailto: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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