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    Building, troubleshooting and testing of these amplifiers should only be
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Vacuum tube parameters - Educate me

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I am looking for alternatives to existing sweep tubes. Obviously there is a pinout difference which does not need to be explained.

But how do I determine if something is a good match?

Power Handling
1) How do I determine how many watt's a tube can put out/endurance? Do I look at plate dissipation? Screen dissipation? Plate Voltage? Screen supply voltage? Do I look at the Vf and amperage?
2) What does this even mean Vf 6.3 Volts / If 0.22 Ampere? The If 0.22 part... Is that the voltage it's comfortable at with that amperage? Or is that only a endurance value? So for example could I replace a Vf 6.3 Volts / If 0.22 Ampere with a Vf 9 Volts / If 0.22 Ampere tube?

Myriad of other parameters
There are a ton of other parameters so long I don't even want to list. What are the vital ones for a person simply trying out new tubes?

Can I use a half-wave vacuum rectifier tube in place of a Beam Power Tube?
So many choices...power triode, small-signal pentode, hexode, heptode, thyratron, enneode, single gasfilled rectifier diode, etc... What can safely be swapped out?
 
I am looking for alternatives to existing sweep tubes.

Why? Is this for a particular amplifier?

Can I use a half-wave vacuum rectifier tube in place of a Beam Power Tube?
So many choices...power triode, small-signal pentode, hexode, heptode, thyratron, enneode, single gasfilled rectifier diode, etc... What can safely be swapped out?

No, you replace a power tube with another power tube. A rectifier tube is for converting AC to DC.


jeff
 
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Joined 2008
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I am looking for alternatives to existing sweep tubes. Obviously there is a pinout difference which does not need to be explained.

But how do I determine if something is a good match?

Power Handling
1) How do I determine how many watt's a tube can put out/endurance? Do I look at plate dissipation? Screen dissipation? Plate Voltage? Screen supply voltage? Do I look at the Vf and amperage?

2) What does this even mean Vf 6.3 Volts / If 0.22 Ampere? The If 0.22 part... Is that the voltage it's comfortable at with that amperage? Or is that only a endurance value? So for example could I replace a Vf 6.3 Volts / If 0.22 Ampere with a Vf 9 Volts / If 0.22 Ampere tube?

Myriad of other parameters
There are a ton of other parameters so long I don't even want to list. What are the vital ones for a person simply trying out new tubes?

Can I use a half-wave vacuum rectifier tube in place of a Beam Power Tube?
So many choices...power triode, small-signal pentode, hexode, heptode, thyratron, enneode, single gasfilled rectifier diode, etc... What can safely be swapped out?

There are different ways to answer the first question. I'd suggest you start by looking at some of these posts. One or two of them will be easier to understand than others. Which ones depends on your own personal vocabulary and way of thinking.

The second answer is simple in any language. The f in Vf stands for the filament (or heater) voltage. Though there are those who will argue for tweaking those, in general you're best off at first to follow them exactly. So if the power supply for the heaters is 6.3V you should use a tube with heaters that run at 6.3V.

If you were to convert the circuit to suit a tube with 9V heaters you would have to find a way to supply that voltage. Trying to run a 9V tube on 6.3V would mean the cathode would not be hot enough to emit electrons the the way the tube was designed to. Running the heater at higher than spec'd voltage will shorten its life. (In some application notes running the heater at lower voltage is said to shorten the tubes working lifetime)

There are exceptions to this, with some even finding that lowering or raising the voltages results in obtaining desirable characteristics not listed on the data sheet but this part of the tweaking thing is debatable (sometimes hotly) and I wouldn't listen to any of that stuff if you're starting out with tubes.

Also I hope you don't mind throwing in a personal opinion but if I read you right and you're just starting off I think you're best off to build the circuit as designed. Do that and while listening to the results start to read up on the electronics of tube circuits and then work out what changes you want to try. Trying to chew the whole pie at once is an invitation to indigestion which from what I've seen often results in pushing the plate off to the side.
 
Thanks everyone. Pete's original thread is quite long.. I guess I may need to read it to determine what everyone else has used and what is safe. Given the high voltages involved I guess going forward I will play it safe and not experiment on my own.

If you're fairly new to this, one thing you'll need to get used to, is the broad range of confusing 'standard' symbolism, labeling & nomenclature used in tube circuits and publications over the years.

When reading old and/or foreign data sheets, look carefully at the units in use, if you're not sure what a given parameter might indicate. In particular, note the proportional relationship between Siemens (S) and micro-mho (uMho), the Gm (transconductance value). Another good example would be the symbols for voltage: E (EMF), V (Volts) and U (Potential) are identical in meaning. Add to that the fact that a tube plate may be known as either plate or anode (p or a) you get Ep, Ea, Vp, Va, Up and Ua all meaning "plate voltage". Oh, and uA (but not Ua) means "micro amps" to boot.

It's a crapfield.
 
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Pete's original thread is quite long.. I guess I may need to read it to determine what everyone else has used and what is safe. Given the high voltages involved I guess going forward I will play it safe and not experiment on my own.

Yes, it's a long thread, but still worth going thru, especially if you're considering building the amp. For stock power tubes, you're limited to 6JN6 (no top cap anode), or 6JM6/6GV5 (top cap anode). For driver tubes, there are more with the same pin-out and characteristics as the 6CB6, but it seams most people stick with this tube for stock builds.

It's also handy to have the tube data sheets on your computer for reference. You can search and download here: http://www.mif.pg.gda.pl/homepages/frank/vs.html

jeff
 
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Status
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