How about running the bias through the coil of an in line small relay. It is
held in any time the negative voltage is present. The present final cathode to
ground circuit would be run through the normally closed relay points. Loss of
any bias current and the relay cuts off the finals. Boyd
Geoffrey S. Mendelson [EMAIL PROTECTED] made an utterance to the drakelist
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On Sun, Dec 16, 2007 at 10:24:48AM -0500, Mike Bryce wrote:
Do you want to put the protection inside the power supply?
That brings up a
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang
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Ron -
That would work, there would be a pulse of high current, but would fade
pretty quickly as the filaments cooled.
I'd rather avoid a relay, since
Chuck Grandgent [EMAIL PROTECTED] made an utterance to the drakelist gang
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Alright, here's a thought.
If I have the gain / drive level control all the way down (counter
clockwise), and the bias were to fail, would my finals be
Gary Poland [EMAIL PROTECTED] made an utterance to the drakelist gang
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Chuck,
Nothing you can do short of turning the equipment off would prevent the
final tubes to fully conduct if the bias went positive and the VOX trips
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang
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Nope...
If B+, screen and filament voltages are applied, and the cathode is
grounded, the finals will draw however much current the power supply can
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang
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When the bias fails, the finals conduct. The VOX trips because the bias
is ALSO used to bias off the relay tube. Bias gone, the relay tube
conducts,
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang
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Chuck -
You could, but the fuse would have to be able to clear the 650V B+ to
open the circuit. A fuse that is RATED to do this is about six inches
Bill Horne [EMAIL PROTECTED] made an utterance to the drakelist gang
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Is there a provision in the kit for a crowbar circuit to safeguard the
rig if the bias (or other) supply fails?
Bill, W1AC
Chuck Grandgent wrote:
I
Mike Bryce [EMAIL PROTECTED] made an utterance to the drakelist gang
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Gosh..
I thought about that, but here's no way to crowbar the bias circuit.
in the old supplies, the damage is caused by a lack of bias. So, if
there is
In a message dated 12/15/2007 5:45:09 PM Eastern Standard Time,
[EMAIL PROTECTED] writes:
a system that deprives the transformer of it's primary voltage, shutting
down the
supply.
I think I would rather have that than frying a set if finals, or maybe an
audible bias loss alert.
73 and
Mark Pilant [EMAIL PROTECTED] made an utterance to the drakelist gang
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Hi Mike.
the only way I could come up with would have been a system that
deprives the transformer of it's primary voltage, shutting down
the supply.
Jim Shorney [EMAIL PROTECTED] made an utterance to the drakelist gang
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On Sat, 15 Dec 2007 17:44:33 -0500, Mike Bryce wrote:
in the old supplies, the damage is caused by a lack of bias. So, if
there is a failure of the bias
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang
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Mike -
Yeah, it's not as easy to crowbar a 700V power supply as it is a 13.6V one!
Probably simplest is a thyristor across the AC line (after the fuse!
Bill Horne [EMAIL PROTECTED] made an utterance to the drakelist gang
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Mike,
I understand, and perhaps Crowbar is the wrong term: there's certainly
enough technical expertise on the list to suggest a viable circuit.
Here's
This is starting to remind me of my tractor problem.
1950 Ford 8N that is.
The problem is, if you're dumb enough to be around the PTO off the back and
get entangled and hence expire. On a similar board lots of controversy about
how best to protect against these sort of mishaps.
So, I hooked up
Robert Ladden [EMAIL PROTECTED] made an utterance to the drakelist gang
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The first set of caps lasted 30-40 years. Would the new caps last
less than that?
I think it is more likely that the cinch connector would become
Ron Wagner [EMAIL PROTECTED] made an utterance to the drakelist gang
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Gary,
I looked at this some years ago. I had a design started that would drop
the filiament voltage off the rig. Kind of hard to run a tube w/o a
Jim Shorney [EMAIL PROTECTED] made an utterance to the drakelist gang
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On Sat, 15 Dec 2007 20:46:22 -0500, Robert Ladden wrote:
I think it is more likely that the cinch connector would become loose
and the pin that carries
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