[mick]

On Fri, 01 Jan 2010 21:36:09 -0800, Alex wrote:

snip

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part
numbers.



Would it be possible to bias the heater winding to a higher voltage, say
90v? That might allow a far larger choice of bottles.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Ian Bell[_2_]]

Alex wrote:
Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher.

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part numbers.

Thanks in advance!
Regards,
Alex



You might well find it hard to find many more B9A tubes with greater hk
ratings although you might like to look at the 12BH7 but it mu is lower
than that of a 6CG7.

Be careful with these ratings because in many cases they are not dc only
ratings but the sum of dc and peak signal values.

The normal way to work a CF such are you are thinking of is the elevate
the heater voltage to around 75V or so above ground.

Cheers

ian

Cheers

Ian

[sparky]

On Jan 2, 12:36*am, "Alex" wrote:
Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher..

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part numbers.

Thanks in advance!
Regards,
Alex

Can you use a separate transformer for this heater?
That would solve your heater-cathode voltage problems.

[Alex]

Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher.

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part numbers.

Thanks in advance!
Regards,
Alex

[Patrick Turner]

On Jan 2, 4:36*pm, "Alex" wrote:
Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher..

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part numbers.

Thanks in advance!
Regards,
Alex


If you are worried about heater-cathode voltages causing arcs or
leakage, then make a floating dc heater supply which has a 100k
resistance from the cathode to the negative side of the heater supply.
The 100k will keep the heater voltage close to the cathode Vdc and
Vac. The only trouble is that if the heater supply transformer winding
is close to a mains winding then you'll have maybe some mains hum
noise transfered to the cathode via the small amount of capacitance
between windings. So you may need to bypass the heater supply to 0V
via maybe 2uF which will charge up quickly. But then you effectively
have a 100k + 2uF from cathode to 0V which may upset the signal
working.

Another method is to have a 6.3Vac : 6.3Vac transformer from an
existing heater supply and arrange the secondary to have an
electrostatic screen. Stray C is reduced to less than 75pF. The
winding can have a CT and this is then connected to the cathode via
say 10k to bias the winding.

I have never ever needed to do such tricky things in any amplifier and
I've never seen it done in any of many amps or gear I have have
serviced. If you need to use such techniques, you should have become
aware of the extra country miles you gotta travel to make sure the
gear remains smoke and noise free.

6U8A and many video triode pentodes used in TV applications will have
high gm you say you want.
I suggest you browse other listed tri-pents in the old tube manuals.

I never trust the 200Vdc rating for heater cathode voltages and I
would always want the Ek-h to be less than 75V.
I've seen failures in amps where stupid designers have had over 200V
on triodes rated for only 90V.

Patrick Turner.

[Patrick Turner]

On Jan 3, 7:39*am, "Alex" wrote:
"flipper" wrote in message

news




On Fri, 1 Jan 2010 21:36:09 -0800, "Alex" wrote:

Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the
detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher.

As others have mentioned the traditional method is to bias the heater
voltage but, making a guess from your numbers, there are some circuit
tricks you could maybe use.

The first obvious one is to prevent load removal. I.E. a permanent
load in parallel with the one that might be removed.

Second, put a SS diode from grid (diode anode) to cathode (diode
cathode). That will pull down the driver tube's load (since it will
drive into the CF load) when the tubes are non conducting keeping grid
and cathode V low until they both conduct, at which point the diode
drops out and the circuit operates normally. Your concern there is the
nominal operating voltage on the follower (when operating) if all
other tubes are removed (I.E. maximum power supply float under minimum
load) but with the numbers given I'm guessing that should not be a
problem.

Having said that, it's debatable whether 'start up' is as much of a
problem as it might seem because, with no current flow, cathode is not
'high' despite high grid V but the diode makes the issue moot.

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part
numbers.

200V is the normal 'max' and the only thing I can recall higher was a
power pentode. The more common case is lower, like with some intended
for (U.S.) 'line power'.

Note, that *is* total DC and signal peak, for heater negative (your
case). With heater positive it's 100VDC, peaks to 200V.

Thanks. Though the silicon diode will not help from the load disconnection,
it might help reduce positive bias on a cold tube.

Well, I ended up using a pentode section of 6BX8 in a triode connection. It
has plenty of current, a decent transconductance for low output impedance..
Triode connection mu is not directly quoted in the datasheet, but from the
other operation point numbers it must be somewhere around 40, which is good.
In all respects it is better than 6CG7 triode.

Some disadvantage -- this tube is rather hungry on the heater: 0.75A.

Regards,
Alex- Hide quoted text -

- Show quoted text -

I much like to use EL84 or EL86 as driver triodes for output tubes.

An EL84 typical triode set up is Ea = 250V, Ia = 15mA, giving Ra =
2k2, µ = 17, so gm = 7.7mAV.

This is about like using 5 half triode sections of a 6CG7 all in
parallel.

The EL86 has Ra = about 1k5 and µ = 10, so gain is less, but hey, Ra
is *very* low.
6CL6 is another choice....

Linearity is at least as good as 6CG7.

If you wish to use EL84 as a CF or have a pair in µ-follower, and you
have one cathode at +250V, then follow what I said before in a post
about dedicated heater windings. Or bias a common heater supply up to
+125V, which means you'll have 125V Vh-k difference for the top and
bottom triodes. Or if you have a CF after a typical common cathode
gain tube, use a negative -250V supply for the cathode load of the CF
and CR couple the gain tube anode to the CF grid which is biased at
0V.

Patrick Turner.

[Alex]

"flipper" wrote in message
news
On Fri, 1 Jan 2010 21:36:09 -0800, "Alex" wrote:

Hello,
I would ask for an advice from the tube experts.

I need a double triode or a triode-pentode with high cathode-to-heater
voltage rating, 200...250V.
Cathode current -- not less than 15mA. Transconductance -- as large as
possible. Amplification mu -- as large as possible, but not to the
detriment
of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V.

One section of this tube is to be used as a cathode follower. Under steady
state conditions cathode voltage is expected to be around 80...110V, but
during warm-up, transients or pull-down load removal it might rise higher.

As others have mentioned the traditional method is to bias the heater
voltage but, making a guess from your numbers, there are some circuit
tricks you could maybe use.

The first obvious one is to prevent load removal. I.E. a permanent
load in parallel with the one that might be removed.

Second, put a SS diode from grid (diode anode) to cathode (diode
cathode). That will pull down the driver tube's load (since it will
drive into the CF load) when the tubes are non conducting keeping grid
and cathode V low until they both conduct, at which point the diode
drops out and the circuit operates normally. Your concern there is the
nominal operating voltage on the follower (when operating) if all
other tubes are removed (I.E. maximum power supply float under minimum
load) but with the numbers given I'm guessing that should not be a
problem.

Having said that, it's debatable whether 'start up' is as much of a
problem as it might seem because, with no current flow, cathode is not
'high' despite high grid V but the diode makes the issue moot.

To be on a safer side I would like to use a tube with 200...250V
cathode-to-heater rating.

So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating.

I hope many of you, tube gurus, can easily quote more suitable part
numbers.

200V is the normal 'max' and the only thing I can recall higher was a
power pentode. The more common case is lower, like with some intended
for (U.S.) 'line power'.

Note, that *is* total DC and signal peak, for heater negative (your
case). With heater positive it's 100VDC, peaks to 200V.

Thanks. Though the silicon diode will not help from the load disconnection,
it might help reduce positive bias on a cold tube.

Well, I ended up using a pentode section of 6BX8 in a triode connection. It
has plenty of current, a decent transconductance for low output impedance.
Triode connection mu is not directly quoted in the datasheet, but from the
other operation point numbers it must be somewhere around 40, which is good.
In all respects it is better than 6CG7 triode.

Some disadvantage -- this tube is rather hungry on the heater: 0.75A.

Regards,
Alex

[Patrick Turner]

On Jan 4, 6:55*am, "Alex" wrote:
"flipper" wrote in message

...





On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:

"flipper" wrote in message

Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.

Sorry. A typo. Meant 6DX8.

Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage..

I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.

About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?).

This is a fair question. Why do many noval base tri-pents and many
others all have different damn pinouts?
Why is it that there are many different railway guages and screw
threads in the world when it would obviously be much more convenient
for everyone if standard rail gauge was 4ft 8.5inch world wide and if
the only metal threads were Metric threads which IMHO are the best,
ie, the pitch is neither too fine or two coarse regardless of the
application?

Well, deliberate non conformist pin-outs, rail gauges and threads were
all chosen to make sure a given radio could only be fitted with
certain tubes and no others, and that only certain railway rolling
stock could be used and only threads chosen by a manufacturer could be
used. Such hegemony upon homogenious sizes and pinouts mean that once
someone buys an RCA radio or TV set, only RCA tubes can be fitted, and
once someone signs up to having say the broad gauge used in the USA
then that's where they must buy the trains from, and the service
packages. Ditto with threads on screws. If a country buys a Boeing
aeroplane, then they must consequently use Boeing spare nuts and
bolts, even though other cheaper speare parts brands might be quite
suitable. Of course despite the lack of engineering standardization
found world wide it has not prevented many bogus makers of parts for
all sorts of things like companies with names like Phake-Aero-Parts P/
L, and if you were to examine aeroplane servicing with a magnifying
glass you'd find many planes are flying around with nuts and bolts
which are half the strength they should be. Some planes have
highlighted the problem after falling from the sky. But I digress.

Sometimes there are good reasons why triode-pentodes, or frequency
converter tubes such as 6BE6 or 6AN7 have pin-outs different to
substitutes, and mainly because the subs are not quite the same, and
not real subs unless the circuit has a few real changes made to coils
or R&C values to make things work best over a certain RF range.

There is now a vast number of solid state integrated chips with more
than 8 pins. And a vast number of applications or functions for such
chips so having similar pinouts becomes a meaningless advantage to
anyone. So as complexity of devices went beyond the garden variety
twin triode we just didn't really need pin out compatibility.

And in any case, with tri-pents or twin triodes with equal gain
sections **it is not hard to change the socket wiring** to suit a
different tube if we wish to switch say from 6CG7 to 12AU7, etc.
BTW, usually 6DJ8/6922 are compatible in circuits designed for 6CG7
with *one major exception*, ie, the Ea used for the tube. 6CG7 have
almost identical electronic rating data to 6SN7 so the Ea max could be
up to around 300V without dange of arc overs within the tube. But I'd
always limit Ea in 6DJ8 to 150V. In fact, I'd only want to use 6DJ8 in
a power amp as an input triode in SE mode or as an input LTP balanced
pair where the Ea is fine at 100V, and Ia can then be a healthy and
safe 6mA so that you get a nice 5Vrms output from a low Ra device to
drive a driver stage using something such as 6CG7, 12BH7, 12AU7, 6SN7,
EL84, EL34 etc, but which are better suited to producing up to 100Vrms
output with Ea a typical +250V.

Patrick Turner.


So far the mains transformer is not
overly hot and heater voltage (6.1Vac) is still reasonable. However the
tranny is struggling a bit at warm-up. Pilot globe is noticeably dimmer on
turn on. Well, better for the tubes -- less inrush current. If later I find
I need to reduce power consumption, I will take the trouble to rewire.



At 450mA heater power there's the 6JW8 with a triode at 70 but the
pentode is only 1.2W. And the 6CM8 with a triode at 100 and a 2W
pentode. But gm is lower for both compared to the others.

If you're going to burn 750mA, though, why not the 6LY8? Triode is 100
and gm on the pentode is 20k. I almost used those in my 'PC Speaker'
amp but it was too much power.

6LY8 sounds exotic. I do not have such a beast in my collection. Must be
just pre-tube-extinction release.

Regards,
Alex- Hide quoted text -

- Show quoted text -

[Alex]

"flipper" wrote in message

Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.

Sorry. A typo. Meant 6DX8.

Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.

[Alex]

"Patrick Turner" wrote in message
...


If you are worried about heater-cathode voltages causing arcs or
leakage, then make a floating dc heater supply which has a 100k
resistance from the cathode to the negative side of the heater supply.
The 100k will keep the heater voltage close to the cathode Vdc and
Vac. The only trouble is that if the heater supply transformer winding
is close to a mains winding then you'll have maybe some mains hum
noise transfered to the cathode via the small amount of capacitance
between windings. So you may need to bypass the heater supply to 0V
via maybe 2uF which will charge up quickly. But then you effectively
have a 100k + 2uF from cathode to 0V which may upset the signal
working.

Another method is to have a 6.3Vac : 6.3Vac transformer from an
existing heater supply and arrange the secondary to have an
electrostatic screen. Stray C is reduced to less than 75pF. The
winding can have a CT and this is then connected to the cathode via
say 10k to bias the winding.

I have never ever needed to do such tricky things in any amplifier and
I've never seen it done in any of many amps or gear I have have
serviced. If you need to use such techniques, you should have become
aware of the extra country miles you gotta travel to make sure the
gear remains smoke and noise free.

6U8A and many video triode pentodes used in TV applications will have
high gm you say you want.
I suggest you browse other listed tri-pents in the old tube manuals.

Yes, many oscillator-mixer tubes are suitable, 6AN8, 6AW8, 6EA8, 6JW8, but
they are marginal in terms of power dissipation. The best from my junk box
was 6DX8: video pentode (4W plate) + triode with mu=65.

I never trust the 200Vdc rating for heater cathode voltages and I
would always want the Ek-h to be less than 75V.
I've seen failures in amps where stupid designers have had over 200V
on triodes rated for only 90V.

My greatest sin though is that this is not for an amplifier. I am rebuilding
a vintage sweep-oscillator. It has magnetic frequency modulation -- RF coils
are wound on ferrite rods between the poles of an electro-magnet with
permanent nagnet bias.

from the modern view point, the design is quite brainless -- frequency
modulation (sweep) is sinusoidal, just by applying mains voltage to the
electro-magnet coil. Instead of that I will make a saw-tooth modulation.
like a vertical deflection TV circuit at a lower frequency, say 10Hz (10
sweeps per second).

The cathode follower (CF) in question is for the RF oscillator amplitude
stabilisation by way of anode modulation. CF load is virtually the whole RF
oscillator circuit. Yes it is boot-strapped, so to get the highest gain I
would like to have higher mu in the CF, as well as high transconductance.

Perhaps I might the CF pentode as a pentode and boot-strap the whole screen
grid of the CF, not only the load resistor of the previous stage (error
amplifier). Probably this will give even higher gain. What do you think?

Since number of the tube sockets is limited, I have to use combined tubes --
single EL84 per socket would be an unaffordable luxury. I need to squeeze a
saw-tooth oscillator and the final "deflection" stage as well.

Regards,
Alex

[Ian Bell[_2_]]

flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner
wrote:

On Jan 4, 6:55 am, "Alex" wrote:
"flipper" wrote in message

...





On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:
"flipper" wrote in message
Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.
Sorry. A typo. Meant 6DX8.
Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.
I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.
About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?).
This is a fair question. Why do many noval base tri-pents and many
others all have different damn pinouts?
Why is it that there are many different railway guages and screw
threads in the world when it would obviously be much more convenient
for everyone if standard rail gauge was 4ft 8.5inch world wide and if
the only metal threads were Metric threads which IMHO are the best,
ie, the pitch is neither too fine or two coarse regardless of the
application?

Well, deliberate non conformist pin-outs, rail gauges and threads were
all chosen to make sure a given radio could only be fitted with
certain tubes and no others, and that only certain railway rolling
stock could be used and only threads chosen by a manufacturer could be
used. Such hegemony upon homogenious sizes and pinouts mean that once
someone buys an RCA radio or TV set, only RCA tubes can be fitted, and
once someone signs up to having say the broad gauge used in the USA
then that's where they must buy the trains from, and the service
packages. Ditto with threads on screws. If a country buys a Boeing
aeroplane, then they must consequently use Boeing spare nuts and
bolts, even though other cheaper speare parts brands might be quite
suitable. Of course despite the lack of engineering standardization
found world wide it has not prevented many bogus makers of parts for
all sorts of things like companies with names like Phake-Aero-Parts P/
L, and if you were to examine aeroplane servicing with a magnifying
glass you'd find many planes are flying around with nuts and bolts
which are half the strength they should be. Some planes have
highlighted the problem after falling from the sky. But I digress.

Pure crap.

Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are
they the only ones that use them and while radio and TV set of the era
often admonished to "use only insert brand tubes" virtually every
tube type was made by everyone.

As for rail gauge, every one of them was chosen for technical reasons
that, at the time, seemed appropriate to the governing authorities and
the U.S., as of 1863 (except the South), uses Standard/International
gauge, not broad gauge. The South used broad gauge until 1886 when, in
the stunning record time of 36 hours, the entire South was converted
to Standard.


Yes, but of course that is only in the USA which as we all know is only
a very small part of the world and not the centre of the universe as
some seem to think.

Cheers

Ian

[Don Pearce[_3_]]

On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote:

On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell
wrote:

flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner
wrote:

On Jan 4, 6:55 am, "Alex" wrote:
"flipper" wrote in message

...





On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:
"flipper" wrote in message
Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.
Sorry. A typo. Meant 6DX8.
Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.
I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.
About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?).
This is a fair question. Why do many noval base tri-pents and many
others all have different damn pinouts?
Why is it that there are many different railway guages and screw
threads in the world when it would obviously be much more convenient
for everyone if standard rail gauge was 4ft 8.5inch world wide and if
the only metal threads were Metric threads which IMHO are the best,
ie, the pitch is neither too fine or two coarse regardless of the
application?

Well, deliberate non conformist pin-outs, rail gauges and threads were
all chosen to make sure a given radio could only be fitted with
certain tubes and no others, and that only certain railway rolling
stock could be used and only threads chosen by a manufacturer could be
used. Such hegemony upon homogenious sizes and pinouts mean that once
someone buys an RCA radio or TV set, only RCA tubes can be fitted, and
once someone signs up to having say the broad gauge used in the USA
then that's where they must buy the trains from, and the service
packages. Ditto with threads on screws. If a country buys a Boeing
aeroplane, then they must consequently use Boeing spare nuts and
bolts, even though other cheaper speare parts brands might be quite
suitable. Of course despite the lack of engineering standardization
found world wide it has not prevented many bogus makers of parts for
all sorts of things like companies with names like Phake-Aero-Parts P/
L, and if you were to examine aeroplane servicing with a magnifying
glass you'd find many planes are flying around with nuts and bolts
which are half the strength they should be. Some planes have
highlighted the problem after falling from the sky. But I digress.

Pure crap.

Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are
they the only ones that use them and while radio and TV set of the era
often admonished to "use only insert brand tubes" virtually every
tube type was made by everyone.

As for rail gauge, every one of them was chosen for technical reasons
that, at the time, seemed appropriate to the governing authorities and
the U.S., as of 1863 (except the South), uses Standard/International
gauge, not broad gauge. The South used broad gauge until 1886 when, in
the stunning record time of 36 hours, the entire South was converted
to Standard.


Yes, but of course that is only in the USA which as we all know is only
a very small part of the world and not the centre of the universe as
some seem to think.

The "broad gauge used in the USA" is what he referenced so that's what
I spoke directly to.

When Stevenson invented his broad gauge here in the UK, he did a
safety test that involved a complete train with steam loco and a
broken rail on a high embankment. The train derailed (obviously) and
ran down the embankment. The whole train remained upright during the
test, and he was very upset when he was forced to conform to standard
gauge for his railways.

The bean counters had won again.

d

[Don Pearce[_3_]]

On Sun, 03 Jan 2010 11:15:02 GMT, (Don Pearce) wrote:

When Stevenson invented his broad gauge here in the UK, he did a
safety test that involved a complete train with steam loco and a
broken rail on a high embankment. The train derailed (obviously) and
ran down the embankment. The whole train remained upright during the
test, and he was very upset when he was forced to conform to standard
gauge for his railways.

I meant Brunel, of course.

d

[Alex]

"flipper" wrote in message
...
On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:


"flipper" wrote in message

Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.

Sorry. A typo. Meant 6DX8.

Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.


I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.

About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?). So far the mains transformer is not
overly hot and heater voltage (6.1Vac) is still reasonable. However the
tranny is struggling a bit at warm-up. Pilot globe is noticeably dimmer on
turn on. Well, better for the tubes -- less inrush current. If later I find
I need to reduce power consumption, I will take the trouble to rewire.


At 450mA heater power there's the 6JW8 with a triode at 70 but the
pentode is only 1.2W. And the 6CM8 with a triode at 100 and a 2W
pentode. But gm is lower for both compared to the others.

If you're going to burn 750mA, though, why not the 6LY8? Triode is 100
and gm on the pentode is 20k. I almost used those in my 'PC Speaker'
amp but it was too much power.

6LY8 sounds exotic. I do not have such a beast in my collection. Must be
just pre-tube-extinction release.

Regards,
Alex

[Alex]

"Patrick Turner" wrote in message
...

Patrick:
There is now a vast number of solid state integrated chips with more
than 8 pins. And a vast number of applications or functions for such
chips so having similar pinouts becomes a meaningless advantage to
anyone. So as complexity of devices went beyond the garden variety
twin triode we just didn't really need pin out compatibility.

Alex:
Thanks goodness (or whatever it is) that pinouts of the operational
amplifiers in SO-8 and SO-14 and smaller packages are standardised, also
transistors and MOSFETs in TO-126, TO-251, TO-252, TO-220, TO-263, SOT-23,
SOT-223, etc.

[Alex]

"flipper" wrote in message

The 6DX8's 9HX basing seems to be the 'oddball' as there's a whole
slew of triode pentode pairs with 9DX basing.

Could you please explain what "9HX basing" and "9DX basing" means?

[Alex]

"flipper" wrote in message
...
On Sun, 3 Jan 2010 17:56:17 -0800, "Alex" wrote:


"flipper" wrote in message

The 6DX8's 9HX basing seems to be the 'oddball' as there's a whole
slew of triode pentode pairs with 9DX basing.

Could you please explain what "9HX basing" and "9DX basing" means?


That's the EIA designation of the pinout 'standard'. For example, the
'same pin out' you mentioned for twin triodes is 9A (with 'half
heater' pin 9), 9AJ (pin 9 is internal shield), and 9LP (no connection
pin 9). They're not really identical but if you use pin 4-5 heater and
NC on pin 9 they're 'compatible'.

The 5670 twin triode is completely different, however, with 8CJ pinout
and the 20EZ7 (20V heater 12AX7 for 'low cost stereos) is 9PG
(possibly to move the heater pins for, hopefully, less hum
susceptibility). I used the 20EZ7 in Tin Man.

That number is usually located under/near the pin drawing on the tube
datasheet.

If you use Duncan's TDSL program you can search by pinout so, for
example, you could locate all triode pentode pairs with 9DX. At least,
all the ones his program knows about. That's what I did and observed
few results for 9HX.

I did that when I was contemplating the 'PC Speaker' amp because I
considered making a PCB and having 'a lot of choices' seemed like it
might be a good thing. That 6LY8 is also a 9DX, and the 6CX8, and the
6JE8, 6KR8, 6AU8, 6JV8 etc.

Actually, the 6JV8 is almost identical to the 6AW8 and works as a
direct sub in my 'PC Speaker' amp. The others would need component
changes.

Thanks,
This is very useful. I installed that TDSL search program.

[Patrick Turner]

On Jan 3, 6:42*pm, flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner





wrote:
On Jan 4, 6:55 am, "Alex" wrote:
"flipper" wrote in message

. ..

On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:

"flipper" wrote in message

Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.

Sorry. A typo. Meant 6DX8.

Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.

I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.

About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?).

This is a fair question. Why do many noval base tri-pents and many
others all have different damn pinouts?
Why is it that there are many different railway guages and screw
threads in the world when it would obviously be much more convenient
for everyone if standard rail gauge was 4ft 8.5inch world wide and if
the only metal threads were Metric threads which IMHO are the best,
ie, the pitch is neither too fine or two coarse regardless of the
application?

Well, deliberate non conformist pin-outs, rail gauges and threads were
all chosen to make sure a given radio could only be fitted with
certain tubes and no others, and that only certain railway rolling
stock could be used and only threads chosen by a manufacturer could be
used. Such hegemony upon homogenious sizes and pinouts mean that once
someone buys an RCA radio or TV set, only RCA tubes can be fitted, and
once someone signs up to having say the broad gauge used in the USA
then that's where they must buy the trains from, and the service
packages. Ditto with threads on screws. If a country buys a Boeing
aeroplane, then they must consequently use Boeing spare nuts and
bolts, even though other cheaper speare parts brands might be quite
suitable. Of course despite the lack of engineering standardization
found world wide it has not prevented many bogus makers of parts for
all sorts of things like companies with names like Phake-Aero-Parts P/
L, and if you were to examine aeroplane servicing with a magnifying
glass you'd find many planes are flying around with nuts and bolts
which are half the strength they should be. Some planes have
highlighted the problem after falling from the sky. But I digress.

Pure crap.

Its not pure crap at all.

I recently watched an accurate documentary where forensic crash
experts determined that 3 of four bolts which held a tail rudder
assembly onto a Norwegian plane were fake parts which broke due to
being half the strength they should have been. The plane fell from the
sky. Subsequent investigations in the US found fake parts had been
installed on many planes including Air Force One, the US presidential
plane.

There are now firmer govt regulations in place concerning fake
aircraft parts.



Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are
they the only ones that use them and while radio and TV set of the era
often admonished to "use only insert brand tubes" virtually every
tube type was made by everyone.

Yes sure, but there is much pin-out disparity between many triode-
pentodes used in many TV sets so that substitution is impossible
without rewiring the socket, let alone other circuit mods. It'd have
been easier for all if all tri-pents always had the same pin outs for
the same electrodes.

As for rail gauge, every one of them was chosen for technical reasons
that, at the time, seemed appropriate to the governing authorities and
the U.S., as of 1863 (except the South), uses Standard/International
gauge, not broad gauge. The South used broad gauge until 1886 when, in
the stunning record time of 36 hours, the entire South was converted
to Standard.

Not so stunning really. The sleepers used for standard guage were
shorter than for broad gauge, so they cost less.
By 1886, there was no fear between north and south states of the USA
that an invasion would happen. The nth and sth had finished fighting
in 1865. Many of the nth and sth hate each other's guts to this day of
course which shows there is not complete standardisation of emotional
response between nth and sth.

Meanwhile in Oz which has always had a tiny population but a land area
nearly the size of Nth America. There were quite a number of different
rail gauges for a long time before and after Oz had a Federal Govt in
1901. Before 1901, nobody could be sure there would not be a war
between the States of Australia which were in effect like different
countries under British umbrella rule. Ppl in Victoria didn't want
trains full of tropps to be able to be shipped down from New South
Wales. So the Victorians had broad guage, 5'3", NSW had standard,
4"8.5". Meanwhile in Queeensland the gauge was 3'6", and stopped
invasion from NSW. Also Qld was a very large state, very low
population and the cost of sleepers was a major concern and of course
the sleepers were prone to termites, not to mention the whole rail
system being sunject to regular flood damage.
Victoria was the smallest sized state but had a vast abundance of
eucalypt hardwoods which made ideal rail sleepers so the costs of them
being longer didn't worry the Victorians. Melbourne was the effective
capitol of Australia and the main economic centre before the states
became officially united.
Eventually after many years you could get a train trip from Sydney to
Melbourne without the delays caused by changing bogies on carriages at
the border crossings. Vic went to standard.

It would be a dull world if everything was standardized.

Some things, like women, could never be standardized.

Patrick Turner.

[Patrick Turner]

On Jan 3, 10:15*pm, (Don Pearce) wrote:
On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote:
On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell
wrote:

flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner
wrote:

On Jan 4, 6:55 am, "Alex" wrote:
"flipper" wrote in message

om...

On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:
"flipper" wrote in message

snip,

The "broad gauge used in the USA" is what he referenced so that's what
I spoke directly to.

When Stevenson invented his broad gauge here in the UK, he did a
safety test that involved a complete train with steam loco and a
broken rail on a high embankment. The train derailed (obviously) and
ran down the embankment. The whole train remained upright during the
test, and he was very upset when he was forced to conform to standard
gauge for his railways.

The bean counters had won again.

Yes, but testing trains and making conclusions about the guage and
overturning moments during derailments was a very imprecise science
indeed at the time of Stevenson.

The bean counters soon realised that standard guage rolling stock
construction costs could be reduced significanly with shorter axel
length. So muct so that for a given British Pound, much more rolling
stock could be made and the gains outweighed the advanatges of broad
guage instability.

Later during the peak of rail use in the 1950s where train speeds had
increased to above 100MPH there was **** all safety advantage to be
had by making rails wider apart, even though one could have had wider
rolling stock with more floor area for more ppl or freight.

The same sort of thinking applies to motor vehicles where the maximum
width of a truck is about only 8 feet. We make our highways smooth and
straight and the wheels can be close together.

If you double the width of a train or truck, the costs of railways and
roads soar way to high. If wider vehicles were allowed such as 15'
wide Cadilacs with 12 seats, you'd still get ppl trying to drive one
to work on road lanes 20' wide. Its been decided its more efficient to
have lots of slim width vehicles following each other in series than
half the number at double the width for the same road / track area.

But on another planet Moduxium, in a distant galaxy they don't bother
with wheels; they just have toobs where people stand for a few seconds
before they are beamed up or down to the thousands of height levels of
the population.


Patrick Turner.

[Patrick Turner]

On Jan 4, 6:12*am, flipper wrote:
On Sun, 03 Jan 2010 11:15:02 GMT, (Don Pearce) wrote:
On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote:

On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell
wrote:

flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner
wrote:

On Jan 4, 6:55 am, "Alex" wrote:
"flipper" wrote in message

news:119uj59m68tjspq0erc8geu6ehi61n0gfe@4ax. com...

On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote:
"flipper" wrote in message
Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm
6700, 400mA heater.
Sorry. A typo. Meant 6DX8.
Video pentode, connected as a triode, makes a cathode follower.
Triode section, quite not useless, with mu=65, works in another stage.
I don't know how much 'power' you need out of it but you might want to
look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then
there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W
Pentode.
About 2.5W would be enough with some margin.

Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar
to 6DX8 for both triode and pentode. What is frustrating -- pinout is
TOTALLY different, and I have already wired for 6DX8, which does the job
fine. (Sometimes I wonder why not make the tubes of similar application pin
compatible, as most of double triodes?).
This is a fair question. Why do many noval base tri-pents and many
others all have different damn pinouts?
Why is it that there are many different railway guages and screw
threads in the world when it would obviously be much more convenient
for everyone if standard rail gauge was 4ft 8.5inch world wide and if
the only metal threads were Metric threads which IMHO are the best,
ie, the pitch is neither too fine or two coarse regardless of the
application?

Well, deliberate non conformist pin-outs, rail gauges and threads were
all chosen to make sure a given radio could only be fitted with
certain tubes and no others, and that only certain railway rolling
stock could be used and only threads chosen by a manufacturer could be
used. Such hegemony upon homogenious sizes and pinouts mean that once
someone buys an RCA radio or TV set, only RCA tubes can be fitted, and
once someone signs up to having say the broad gauge used in the USA
then that's where they must buy the trains from, and the service
packages. Ditto with threads on screws. If a country buys a Boeing
aeroplane, then they must consequently use Boeing spare nuts and
bolts, even though other cheaper speare parts brands might be quite
suitable. Of course despite the lack of engineering standardization
found world wide it has not prevented many bogus makers of parts for
all sorts of things like companies with names like Phake-Aero-Parts P/
L, and if you were to examine aeroplane servicing with a magnifying
glass you'd find many planes are flying around with nuts and bolts
which are half the strength they should be. Some planes have
highlighted the problem after falling from the sky. But I digress.

Pure crap.

Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are
they the only ones that use them and while radio and TV set of the era
often admonished to "use only insert brand tubes" virtually every
tube type was made by everyone.

As for rail gauge, every one of them was chosen for technical reasons
that, at the time, seemed appropriate to the governing authorities and
the U.S., as of 1863 (except the South), uses Standard/International
gauge, not broad gauge. The South used broad gauge until 1886 when, in
the stunning record time of 36 hours, the entire South was converted
to Standard.

Yes, but of course that is only in the USA which as we all know is only
a very small part of the world and not the centre of the universe as
some seem to think.

The "broad gauge used in the USA" is what he referenced so that's what
I spoke directly to.

When Stevenson invented his broad gauge here in the UK, he did a
safety test that involved a complete train with steam loco and a
broken rail on a high embankment. The train derailed (obviously) and
ran down the embankment. The whole train remained upright during the
test, and he was very upset when he was forced to conform to standard
gauge for his railways.

The bean counters had won again.

You apparently have the same problem as Patrick in thinking cost is of
no consequence but, besides that, there were other pros and cons in
play.

However, be that as it may be, what you or I think would have been the
'best railroad' isn't the issue. The issue was Patrick's absurdity
that all these decisions were some sort of 'proprietary parts'
conspiracy.- Hide quoted text -

- Show quoted text -

Well, another area where a lack of standardization occurs is with
military gear and ammunition. You just don't want your enemy to steal
your ammo and fire it all back at you through their guns.

Patrick Turner.

[Arny Krueger]

"Patrick Turner" wrote in message


As for rail gauge, every one of them was chosen for
technical reasons that, at the time, seemed appropriate
to the governing authorities and the U.S., as of 1863
(except the South), uses Standard/International gauge,
not broad gauge. The South used broad gauge until 1886
when, in the stunning record time of 36 hours, the
entire South was converted to Standard.

http://en.wikipedia.org/wiki/Broad_gauge

" May 31, 1886. Over a period of 36 hours, tens of thousands of workers
pulled the spikes from the west rail of all the broad gauge lines in the
South, moved them 3 in (76 mm) east and spiked them back in place. The new
gauge was close enough that standard gauge equipment could run on it without
problem. By June 1886, all major railroads in North America were using
approximately the same gauge. The final conversion to true standard gauge
took place gradually as track was maintained."


Not so stunning really. The sleepers used for standard
guage were
shorter than for broad gauge, so they cost less.
By 1886, there was no fear between north and south states
of the USA
that an invasion would happen. The nth and sth had
finished fighting
in 1865. Many of the nth and sth hate each other's guts
to this day of
course which shows there is not complete standardisation
of emotional
response between nth and sth.

Canny observation of life in the US. There has been a lot of cross-migration
between the nth and the sth since the CW, which has tended to mitigate the
hatred or at least break it up into smaller pockets. For example, if you go
south in Florida, you go north culturally. Jacksonville, true to its name is
part of the old South. By the time you get to Miami, it is almost like a
little New YorK City with Cubans standing in for the Puerto Ricans. Go
further south to Key West, and you're culturally in Maine.

Meanwhile in Oz which has always had a tiny population
but a land area
nearly the size of Nth America. There were quite a number
of different
rail gauges for a long time before and after Oz had a
Federal Govt in
1901. Before 1901, nobody could be sure there would not
be a war
between the States of Australia which were in effect like
different
countries under British umbrella rule. Ppl in Victoria
didn't want
trains full of tropps to be able to be shipped down from
New South
Wales. So the Victorians had broad guage, 5'3", NSW had
standard,
4"8.5". Meanwhile in Queeensland the gauge was 3'6", and
stopped
invasion from NSW. Also Qld was a very large state, very
low
population and the cost of sleepers was a major concern
and of course
the sleepers were prone to termites, not to mention the
whole rail
system being sunject to regular flood damage.
Victoria was the smallest sized state but had a vast
abundance of
eucalypt hardwoods which made ideal rail sleepers so the
costs of them
being longer didn't worry the Victorians. Melbourne was
the effective
capitol of Australia and the main economic centre before
the states
became officially united.
Eventually after many years you could get a train trip
from Sydney to
Melbourne without the delays caused by changing bogies on
carriages at
the border crossings. Vic went to standard.

Interesting.

[Patrick Turner]

On Jan 5, 11:06*pm, "Arny Krueger" wrote:
"Patrick Turner" wrote in message



As for rail gauge, every one of them was chosen for
technical reasons that, at the time, seemed appropriate
to the governing authorities and the U.S., as of 1863
(except the South), uses Standard/International gauge,
not broad gauge. The South used broad gauge until 1886
when, in the stunning record time of 36 hours, the
entire South was converted to Standard.

http://en.wikipedia.org/wiki/Broad_gauge

" May 31, 1886. Over a period of 36 hours, tens of thousands of workers
pulled the spikes from the west rail of all the broad gauge lines in the
South, moved them 3 in (76 mm) east and spiked them back in place. The new
gauge was close enough that standard gauge equipment could run on it without
problem. By June 1886, all major railroads in North America were using
approximately the same gauge. The final conversion to true standard gauge
took place gradually as track was maintained."

Not so stunning really. The sleepers used for standard
guage were
shorter than for broad gauge, so they cost less.
By 1886, there was no fear between north and south states
of the USA
that an invasion would happen. The nth and sth had
finished fighting
in 1865. Many of the nth and sth hate each other's guts
to this day of
course which shows there is not complete standardisation
of emotional
response between nth and sth.

Canny observation of life in the US. There has been a lot of cross-migration
between the nth and the sth since the CW, which has tended to mitigate the
hatred or at least break it up into smaller pockets. For example, if you go
south in Florida, you go north culturally. Jacksonville, true to its name is
part of the old South. By the time you get to Miami, it is almost like a
little New YorK City with Cubans standing in for the Puerto Ricans. Go
further south to Key West, and you're culturally in Maine.





Meanwhile in Oz which has always had a tiny population
but a land area
nearly the size of Nth America. There were quite a number
of different
rail gauges for a long time before and after Oz had a
Federal Govt in
1901. Before 1901, nobody could be sure there would not
be a war
between the States of Australia which were in effect like
different
countries under British umbrella rule. Ppl in Victoria
didn't want
trains full of tropps to be able to be shipped down from
New South
Wales. So the Victorians had broad guage, 5'3", NSW had
standard,
4"8.5". Meanwhile in Queeensland the gauge was 3'6", and
stopped
invasion from NSW. Also Qld was a very large state, very
low
population and the cost of sleepers was a major concern
and of course
the sleepers were prone to termites, not to mention the
whole rail
system being sunject to regular flood damage.
Victoria was the smallest sized state but had a vast
abundance of
eucalypt hardwoods which made ideal rail sleepers so the
costs of them
being longer didn't worry the Victorians. Melbourne was
the effective
capitol of Australia and the main economic centre before
the states
became officially united.
Eventually after many years you could get a train trip
from Sydney to
Melbourne without the delays caused by changing bogies on
carriages at
the border crossings. Vic went to standard.

Interesting.- Hide quoted text -

- Show quoted text -

I can never apply one perception of the people of the USA because it
has a diverse range to consider.
Some I like a lot, and others, well, I hope they improove.

Australian people have also become multicultural and largely tolerant
of others within itself.
We could easily be an extra State of the Union, because we speak
english and most of the US media and entertainment has brainwashed us
ever since media and entertainment was invented. Its been a benign
process, augmented by our clinging to Mother England for at least to
about 1960. We'd like to become a Republic, and ditch the Queen of
England as our figurehead monarch, but nobody here knows how to invite
such a nice old lady to leave our Constitutuion. And we sure don't
agree amoung ourselves about what we'd do about having a President;
*whah*, that's way to difficult. Its a case of why change an
antiquated system when it ain't broke, and its fairly harmless as it
is. If we found we had some medling goon of a British royal as Head of
State, then ppl here would push for the adoption of the next least
worse system.

One reason why we never quite ever wanted to fight a civil war over
any damn thing was because by the time you travel to sort it out with
the enemy, you've cooled down, especially considering there are so
many pubs along the way, and its just so far to anywhere in Oz....

Patrick Turner.

[lambwell]

Hello,
I've searched very much but maybe I'm not using good search terms, but I can't find a direct description of how to measure "heater cathode voltage". I mean, seemingly all tubes have a maximum "heater-cathode voltage" which may be X volts positive or negative. Everybody must already know how to measure this or else there would be some better references on the web. I however, do not.
Would someone please point me to a reference of how to measure this parameter or provide their own description?