I understand that the HV needs to be delayed for this tube. If I use a separate switch between my PT CT and ground would a 250VAC switch be sufficient?
Easiest way to get HV delay is using a vacuum tube rectifier instead of a mercury rectifier tube.
Mercury is nasty stuff. Should it evaporate do to an exident the fumes cannot get put back in the glass bottle again, thinck of that!
If you need higher voltages and currents not obtainable with vacuum tubes use Xenon filled tubes instead (same sockets than mercury rectifiers)
Mercury is nasty stuff. Should it evaporate do to an exident the fumes cannot get put back in the glass bottle again, thinck of that!
If you need higher voltages and currents not obtainable with vacuum tubes use Xenon filled tubes instead (same sockets than mercury rectifiers)
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It would be better to have a separate filament transformer and avoid switching the CT in the case of mercury vapor tubes or the xenon filled tubes. You would be switching mostly DC which likes to sustain an arc better than AC. There are time delay relays that can be bought on amazon or other parts suppliers for not so much money also.
With C input, raw dc before the caps goes to zero, so should not be much different to ac, is it?
Anyway, secondary voltage propably exceeds the voltage most switches can handle, so best, as suggested by daqvin_carter, a seperate transformer for the heater and and a timer relay to switch the primary of the hv transformer.
Anyway, secondary voltage propably exceeds the voltage most switches can handle, so best, as suggested by daqvin_carter, a seperate transformer for the heater and and a timer relay to switch the primary of the hv transformer.
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Some Xenon tubes do not necessarelly need delayed hv, others do, mrcury always and need also a defined temeratur rank to work propably.
In addition, MV that have quirks, like backfiring and all kind of unexpected things that are escially disturbing in audio.
If it is the blue glow you are after better settle for the darker one from the xenon gas filled.type.
Back in the days, they have been considered a big improcemt over MV tubes.
Offcourse the non plus ultra where silicon hv replacements as soon as those became avaiable.
In addition, MV that have quirks, like backfiring and all kind of unexpected things that are escially disturbing in audio.
If it is the blue glow you are after better settle for the darker one from the xenon gas filled.type.
Back in the days, they have been considered a big improcemt over MV tubes.
Offcourse the non plus ultra where silicon hv replacements as soon as those became avaiable.
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I guess it would depend on the voltage across the switch. You could wire the two switches of a double pole switch in series to gain some voltage headroom.
Lots of people have done it that way yes, using a suitably heavy-duty switch. Or you could copy the 5F6 Bassman power supply.
http://www.prowessamplifiers.com/schematics/fender/Bassman_5f6-Schematic.html
Correct.
I have been PM-ing with the OP. My HV delay would act as shown in the attachement during an adjustable delay.
Will this fulfil the requirement?
Jan
Will this fulfil the requirement?
Jan
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I believe standby is built into the operation of tube testers. Either you're not expecting to apply HV to the DUT right away, or the 'DC' is just rectified AC with no cap, so no need for a standby.
I have only experience with large MV rectifiers feeding Rf-generator tubes (over 10-12kV, 6-12A dc).
They where ok with a 5min delay when switched (used) on a daily basis, but after the summer, during which the factory was shut down for a couple weeks, at least 15min delay where needed to be sure they will not backfire. Spare tubes, just to make sure, where heated 30min before HV was applied.
They where ok with a 5min delay when switched (used) on a daily basis, but after the summer, during which the factory was shut down for a couple weeks, at least 15min delay where needed to be sure they will not backfire. Spare tubes, just to make sure, where heated 30min before HV was applied.
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MV are prized for their very low voltage drop, this means better sound.
If you have them, use them, with or without a delay.
Of course there is also that blue sexy glow.
If you have them, use them, with or without a delay.
Of course there is also that blue sexy glow.
"Use a time delay valve/tube as they did back in the day. Cheap as chips."
Can you recommend any?
Can you recommend any?
This would do it
https://www.ebay.co.uk/itm/205018578140?customid=&toolid=10050
This is on Ebay UK, I don't know where you are but I'm sure you could find one local to you.
Cetla416a,
I saw your moniker, and a Light[house] triode flashed up on my minds screen.
Love that tube; the 416A was in a great commercial Mono FM tuner we used.
It is my favorite example of a planar triode, with minimal fringe effects, all other fields are equal.
I saw your moniker, and a Light[house] triode flashed up on my minds screen.
Love that tube; the 416A was in a great commercial Mono FM tuner we used.
It is my favorite example of a planar triode, with minimal fringe effects, all other fields are equal.
Are you saying that arc overs would come with a significant risk of blowing the glass ?
By Hot Start Event are you refering to time delay tubes characteristics.
I am not an expert about abusing a mercury vapor rectifier, but I am paranoid, so I "see" broken glass.
A Hot Start Event . . .
Everything is normal, the amplifier is warmed up and running properly.
Then, the power company has a brief power outage, flickering on and off, at different intervals of on and of off, and sometimes with very large transient voltages.
Tube cathodes have thermal inertia, usually lots more thermal inertia than filaments only.
The tube cathode is Hot. Power goes off, the cathode is still Hot when the power comes back on. Bang!
Or, the power goes out, and when it comes back on, the 120VAC has a very fast transient of 300V.
These events are a designers nightmare, and are a repair persons living.
I do my best to protect my power amplifiers.
Transient absorber power strips.
But what about the on, off, on, off, even if there are no transients.
A typical fuse setup for my amplifiers is:
A 1.5A Fast Blow fuse, in series with a 600mA Slow Blow fuse.
The 1.5A protects from inrush currents, at cold power up, and at Hot Start events.
The 600mA slow blow protects when some tube or part draws more than the usual running current, takes a little time, but then it opens up (the more the extra current, the faster it blows).
The amperages are determined by
1. Accurately measuring the power-up inrush current of a cold amplifier, when the switch is closed at the crest of the power mains voltage (120VAC, the crest is at 169.7V peak).
2. Accurately measuring the RMS current of a warmed up running amplifier.
If you pick values that are too high, the protection is reduced.
I came by the need for a 600mA slow blow fuse, when the 0.5 amp slow blow fuse would blow after a week, or even 2 or 3 months of cold amp power-ups.
The 1.5A fast blow was similarly determined, when a 1.25A fuse failed after a few cold amp power-ups.
Attention to details makes it as close as you can get, versus fuse amperage increments.
I know, I am perhaps too serious when it comes to reliability.
My $0.03 adjusted for inflation.
A Hot Start Event . . .
Everything is normal, the amplifier is warmed up and running properly.
Then, the power company has a brief power outage, flickering on and off, at different intervals of on and of off, and sometimes with very large transient voltages.
Tube cathodes have thermal inertia, usually lots more thermal inertia than filaments only.
The tube cathode is Hot. Power goes off, the cathode is still Hot when the power comes back on. Bang!
Or, the power goes out, and when it comes back on, the 120VAC has a very fast transient of 300V.
These events are a designers nightmare, and are a repair persons living.
I do my best to protect my power amplifiers.
Transient absorber power strips.
But what about the on, off, on, off, even if there are no transients.
A typical fuse setup for my amplifiers is:
A 1.5A Fast Blow fuse, in series with a 600mA Slow Blow fuse.
The 1.5A protects from inrush currents, at cold power up, and at Hot Start events.
The 600mA slow blow protects when some tube or part draws more than the usual running current, takes a little time, but then it opens up (the more the extra current, the faster it blows).
The amperages are determined by
1. Accurately measuring the power-up inrush current of a cold amplifier, when the switch is closed at the crest of the power mains voltage (120VAC, the crest is at 169.7V peak).
2. Accurately measuring the RMS current of a warmed up running amplifier.
If you pick values that are too high, the protection is reduced.
I came by the need for a 600mA slow blow fuse, when the 0.5 amp slow blow fuse would blow after a week, or even 2 or 3 months of cold amp power-ups.
The 1.5A fast blow was similarly determined, when a 1.25A fuse failed after a few cold amp power-ups.
Attention to details makes it as close as you can get, versus fuse amperage increments.
I know, I am perhaps too serious when it comes to reliability.
My $0.03 adjusted for inflation.