Re: Sudden B+
- From: "Iain Churches" <IainNG@xxxxxxxxxxx>
- Date: Mon, 11 Feb 2008 19:11:35 +0200
"Patrick Turner" <info@xxxxxxxxxxxxxxxxxx> wrote in message
news:47B068EB.D5ACA218@xxxxxxxxxxxxxxxxxxxxx
Jon Yaeger wrote:
in article EZRrj.7589$x%3.189@trnddc06, West at west@xxxxxxxxxxx wrote on
2/11/08 1:32 AM:
"Iain Churches" <IainNG@xxxxxxxxxxx> wrote in message
news:V_zrj.294813$Fj2.198421@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
on
"Jon Yaeger" <jono_1@xxxxxxxxxxxxx> wrote in message
news:C3D3BFF2.B229E%jono_1@xxxxxxxxxxxxxxxx
in article Farrj.1070$r03.896@trnddc08, West at west@xxxxxxxxxxx
wrote
other2/9/08 7:02 PM:
We have often discussed the merits of having the HV on a delay
circuit.
It's
easy to ramp DC filament voltages with a transistor and a few parts
but
incorporating this type of design with high voltages is somewhat
impractical.
My point and concern is the sudden thump, assault, if you will, on
precious
($$$) valves when the HV kicks in. Having less experience then many
hereRATs, maybe my concern is unwarranted. It's just that I cringe when
all
that
energy comes on so instantly. What do you think? Is there a concern
or
am I picking fly shit out of pepper?
west
Tampa Bay, FL
West,
Do you sit around and try to think up topics for discussion, just to
generate activity and attention? It sure seems that way.
Its better than just digging in for a flame war.
could
Not too long ago there was a thread on cathode stripping, which you
easily check out if you weren't so lame or lazy.
Yes but each time a subject is revisited, the explanations get better.
indirectly
Many designs use a very simple tube solution to delay HV -- an
heated cathode, such as the 5AR4. If you follow them with
recommended
size
caps or a choke input filter, the inrush shouldn't be a problem.
Yes, a tube diode can be used to delay the B+.
I have tried this but I found that in a revised Quad-II. I used silicon
to rectify, and the retired the GZ34 to act as a series slow turn on
diode
where it dissipates less heat than if used as the rectifiers.
But the GZ34 still turn on a lot faster than the KT66, so the B+ tends
to soar
anyway to a full +450V, right on the limits for the electros, before
settling
down to the wanted +375V.
moment
The Eico HF87 also used a bimetallic, resistive strip that took a
isto
heat up and then shorted itself out, reducing inrush further.
Simpler
better.
But when cool the bi-metal is shorted, so at the instant of turn on
there
is a large inrush, no?
Not if the power relay is used to short out a largish series resistor
through which the caps have been charging slowly, until the relay closes.
Electro-mechanical devices which heat up and go twang to do things
like in the old days are more unrelaiable than simple SS and delay RC
circuits
operating of an auxilliary supply of +12V.
:-) The same pair of DLS16 twangers which I fitted some five
years ago are still working impeccably. They only go twang once,
when the amp is powering up. I have every reason to think that
this same pair of twangers may outlive me:-)
The range of delay devices made today are not common,
and I don't like saddling a customer with some device that cannot be
easily
replaced from generic components stores and replaced in 5 minutes.
Agreed. The DLS16 is readily available, but not from a generic
component stores, (but neither is the 6CG7 either:-))
It has an octal socket and so could be changed in 10secs.
Iain
.
- References:
- Sudden B+
- From: West
- Re: Sudden B+
- From: Jon Yaeger
- Re: Sudden B+
- From: Iain Churches
- Re: Sudden B+
- From: West
- Re: Sudden B+
- From: Jon Yaeger
- Re: Sudden B+
- From: Patrick Turner
- Sudden B+
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