Soft Start Problem

W

west

Guest
Gentlemen,
There always seems to be much talk about inrush current being detrimental to
tube filaments, light bulbs, etc. How many of us have turned on a cold light
bulb and have it blow open the filament? A power amplifier's filaments can
draw in excess of 15 steady state amps and much more cold. In tube circuits
the inrush filament current can hasten the life of a tube, some of which can
be rather expensive. Of course a thermister in series with the filament can
alleviate this problem, but it poses other problems, such as increased heat
(especially bad in Florida). If you turn the system on-off-on, the fuse most
likely will open because recycling of the thermistor is slow.
So I am searching for alternate ideas to the thermistor. The HV is no
problem because I simply add a 555 timer that shorts out a power resistor in
series with the B+. The relay activates after the tubes safely warm up.
I've posed this question on my beloved NG, RAT with little satisfaction. I
believe the problem is that this is an electronic, not tube problem. All
suggestions are very welcomed and appreciated. Thank you very much in
advance for you time.
Cordially,
west
 
west wrote:

Gentlemen,
There always seems to be much talk about inrush current being detrimental to
tube filaments, light bulbs, etc. How many of us have turned on a cold light
bulb and have it blow open the filament? A power amplifier's filaments can
draw in excess of 15 steady state amps and much more cold. In tube circuits
the inrush filament current can hasten the life of a tube, some of which can
be rather expensive. Of course a thermister in series with the filament can
alleviate this problem, but it poses other problems, such as increased heat
(especially bad in Florida). If you turn the system on-off-on, the fuse most
likely will open because recycling of the thermistor is slow.
So I am searching for alternate ideas to the thermistor. The HV is no
problem because I simply add a 555 timer that shorts out a power resistor in
series with the B+. The relay activates after the tubes safely warm up.
I've posed this question on my beloved NG, RAT with little satisfaction. I
believe the problem is that this is an electronic, not tube problem. All
suggestions are very welcomed and appreciated. Thank you very much in
advance for you time.
Cordially,
west
Click to expand...
I dont have proof but my thoughts on why a cold light bulb goes poof is......
It was hot when you turned it off and while it was hot some of the hot argon
leaked out. Then when it was turned off and cooled some of the gas was replaced
via the leak with oxygen..........this repeats over time untill there is enough
outside air inside the bulb for the combustion of the tungsten filament.
 
Tim Thomson wrote:

west wrote:

Gentlemen,
There always seems to be much talk about inrush current being detrimental
to tube filaments, light bulbs, etc. How many of us have turned on a cold
light
bulb and have it blow open the filament? A power amplifier's filaments
can
draw in excess of 15 steady state amps and much more cold. In tube
circuits the inrush filament current can hasten the life of a tube, some
of which can be rather expensive. Of course a thermister in series with
the filament can alleviate this problem, but it poses other problems,
such as increased heat (especially bad in Florida). If you turn the
system on-off-on, the fuse most likely will open because recycling of the
thermistor is slow. So I am searching for alternate ideas to the
thermistor. The HV is no problem because I simply add a 555 timer that
shorts out a power resistor in
series with the B+. The relay activates after the tubes safely warm up.
I've posed this question on my beloved NG, RAT with little satisfaction.
I believe the problem is that this is an electronic, not tube problem.
All suggestions are very welcomed and appreciated. Thank you very much in
advance for you time.
Cordially,
west

I dont have proof but my thoughts on why a cold light bulb goes poof
is...... It was hot when you turned it off and while it was hot some of
the hot argon leaked out. Then when it was turned off and cooled some of
the gas was replaced via the leak with oxygen..........this repeats over
time untill there is enough outside air inside the bulb for the combustion
of the tungsten filament.
Click to expand...
On the workbench, whenever we start up an older tube radio rig, we plug it
into a large power reostat. We slowly increase the voltage from zero, up
to the AC operating voltage necessary. The reason for this is:

1. to charge the paper capacitors, slowly, so that the possibly dried-out,
dielectric wax paper is not breached. 'Slowly' means a steady increase
over approximately 5 to 8 seconds, with readiness to immediately stop upon
any strange noise, or smoke!

2. so that the tube 'heater' elements are brought up to full capacity with
'inrush' current limited.

DISCLAIMER !!!
I caution everyone to NOT fool around with any electric / tube type
equipment, AC mains, including monitors, and, television sets, as the
charge built up naturally, in the capacitors, can be of lethal levels
( usually considers as any current above approximately 10 milliamps,
depending upon humidity!) unless experienced, and, you have proper safety
equipment in use!


--
http://safeharbordome.com http://livecdlist.com http://distrowatch.com
http://yolinux.com http://lugww.counter.li.org http://linuxiso.com
 
What he said--with 3 nit-picks:
...whenever we start up an older tube radio rig,
we plug it into a large power reostat.
Wise Linux User

Most folks use a Variac.
Click to expand...
..
..
We slowly increase the voltage from zero, up to the AC operating voltage
...'Slowly' means a steady increase over approximately 5 to 8 seconds

Very old lytics that have been in deep storage
Click to expand...
can be even more temperamental than this.
I have seen (with patience) ancient components (out of the unit
and on a capacitor tester capable of applying variable voltages,
up to the working voltage of the part) come back from the dead
over a period of many, many minutes.
S-L-O-W-L-Y cannot be overemphasized.
..
..
The reason for this is:
1. to charge the paper capacitors, slowly,
so that the possibly dried-out, dielectric wax paper is not breached.

As I suggested above, it's the electrolytics
Click to expand...
that are the most fragile of the things in an old unit.
They must be allowed time for the dielectric layer to "form up";
this is an electrochemical process and mustn't be rushed.
 
May I comment on the eloquence of your irrelevance? The subject matter is
strictly about the filament voltage. Thank you just the same.
west

"Wise Linux User" <duz2600@yahoo.com> wrote in message
news:B%zve.168222$IO.110072@tornado.tampabay.rr.com...
Tim Thomson wrote:

west wrote:

Gentlemen,
There always seems to be much talk about inrush current being
detrimental
to tube filaments, light bulbs, etc. How many of us have turned on a
cold
light
bulb and have it blow open the filament? A power amplifier's filaments
can
draw in excess of 15 steady state amps and much more cold. In tube
circuits the inrush filament current can hasten the life of a tube,
some
of which can be rather expensive. Of course a thermister in series with
the filament can alleviate this problem, but it poses other problems,
such as increased heat (especially bad in Florida). If you turn the
system on-off-on, the fuse most likely will open because recycling of
the
thermistor is slow. So I am searching for alternate ideas to the
thermistor. The HV is no problem because I simply add a 555 timer that
shorts out a power resistor in
series with the B+. The relay activates after the tubes safely warm
up.
I've posed this question on my beloved NG, RAT with little
satisfaction.
I believe the problem is that this is an electronic, not tube problem.
All suggestions are very welcomed and appreciated. Thank you very much
in
advance for you time.
Cordially,
west

I dont have proof but my thoughts on why a cold light bulb goes poof
is...... It was hot when you turned it off and while it was hot some of
the hot argon leaked out. Then when it was turned off and cooled some of
the gas was replaced via the leak with oxygen..........this repeats over
time untill there is enough outside air inside the bulb for the
combustion
of the tungsten filament.

On the workbench, whenever we start up an older tube radio rig, we plug it
into a large power reostat. We slowly increase the voltage from zero, up
to the AC operating voltage necessary. The reason for this is:

1. to charge the paper capacitors, slowly, so that the possibly dried-out,
dielectric wax paper is not breached. 'Slowly' means a steady increase
over approximately 5 to 8 seconds, with readiness to immediately stop upon
any strange noise, or smoke!

2. so that the tube 'heater' elements are brought up to full capacity with
'inrush' current limited.

DISCLAIMER !!!
I caution everyone to NOT fool around with any electric / tube type
equipment, AC mains, including monitors, and, television sets, as the
charge built up naturally, in the capacitors, can be of lethal levels
( usually considers as any current above approximately 10 milliamps,
depending upon humidity!) unless experienced, and, you have proper safety
equipment in use!


--
http://safeharbordome.com http://livecdlist.com http://distrowatch.com
http://yolinux.com http://lugww.counter.li.org http://linuxiso.com
Click to expand...
 
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