I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,
this 813 tube is rated at 250 to 300 watts output RF (per tube), but
running at around 700 to 750 volts on the plate.

I'm not planning to do this, but if this 813 tube was used in an audio
amplifier, and using 700 +/- plate voltage, would this tube be able to
put out around 250 to 300 watts audio power (per tube)? Yea, I know it
would require a custom audio output transformer.

Just curious.....

In article ,
says...

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,
this 813 tube is rated at 250 to 300 watts output RF (per tube), but
running at around 700 to 750 volts on the plate.

I'm not planning to do this, but if this 813 tube was used in an audio
amplifier, and using 700 +/- plate voltage, would this tube be able to
put out around 250 to 300 watts audio power (per tube)? Yea, I know it
would require a custom audio output transformer.

Just curious.....

Froim the data sheeds the 813 is only good for around 350 watts of audio
power with 2 of them in push pull with 2500 volts on the plates. Around
260 watts with 1500 watts on the plates for 2 of them.

I doubt they would make much power at all if only 700 volts were used on
the plates. The tubes are designed for over 1000 volts.

If running in anything resembling linear operation (RF or AF) that is
about all that can be gotten out of them and have them last. Running
class C at RF (audio would be very distorted) you can get more out of
them, but not 250 watts per tube with 700 volts on the plates.

wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


...... Phil

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6, which will not come close to the 6L6GC in
performance.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

Michael Terrell wrote:

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.




..... Phil

Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions. A lot of them were built with W.W. II surplus
tubes, of which the 6L6 was readily available as surplus into the '70s.

We aren't talking about stereos or guitar amps. The were audio
outputs for radios, or modulators for medium power AM transmitters
designed for Amateur radio service. I was servicing these radios back in
the '70s. That is four decades ago.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

Michael Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.



** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.



..... Phil

Phil Allison wrote:
Michael Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.



** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

On 01/03/17 16:26, Michael A. Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the
common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate
voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated
in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low
distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original
6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.



** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this ****ing match?

Clifford Heath wrote:

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this ****ing match?


** I only wanted to point out that regular 6L6 type tubes, as sold in the last 40 years, can output 100W per pair under the right supply conditions - something the data books do not mention.

It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly.

The 813 has fairly similar restrictions on the screen supply voltage.



..... Phil

"It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down. If you go to 2X 700 volts, it might not be a matter of the tubes, it might be the tubes sockets.

What does limiting the G2 do ? Keep it from arcing to the suppressor grid ? I have wondered before about why the hell doesn't all this **** just arc and weld itself together. Well, OK I know it has to do with the vacuum, but still.

However wiki reports that permissivity of air at STP is only something like 1.000 point whatever, with 1 being the standard.

On Wed, 1 Mar 2017 17:18:14 +1100, Clifford Heath
wrote:

** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this ****ing match?

I just referred to the common audio output tubes. Wondering if a
transmitter tube (like an 813) is capable of audio output power in the
same wattage as that same tube would put out as a transmitter (asuming
the plate voltage, biasing, and signal input to the tube was about the
same.

From this thead, I did learn that these tubes need a lot higher plate
voltages than I thought (like 1500 to 2500 volts).

I also learned (after doing some research on the web), that the original
metal 6L6 tubes, did not have the same power output as the glass
version. I NEVER KNEW THERE WAS A DIFFERENCE IN THE
CHARACTERISTICS I thought they were the same tube in a different
container.

*** And this explains something that occurred 40 some years ago. When I
was running my tube power amps for my stereo, (four 6L6GC tubes
Push-Pull Parallel, in each mono block amp), one of the tubes went bad.
I went to my box of used tubes and found a 6L6 metal case, and used that
for a temporary replacement. Although that tube tested GOOD, the amp
just did not sound or perform properly. It did work, but lacked a lot of
the "punch" it had before. A few days later I bought a new 6L6GC, and
the amp worked great once again.

Now, 40 some years later, I learned why that metal 6L6 did not work
properly !!!!

I also learned in recent times that for best performance, a pair or quad
of output tubes should be MATCHED. Back then, I never knew anything
about matching. If it was the proper numbered tube, and a tube that
tested good, I'd just plug it in and GO....

In article ,
says...



I just referred to the common audio output tubes. Wondering if a
transmitter tube (like an 813) is capable of audio output power in the
same wattage as that same tube would put out as a transmitter (asuming
the plate voltage, biasing, and signal input to the tube was about the
same.

From this thead, I did learn that these tubes need a lot higher plate
voltages than I thought (like 1500 to 2500 volts).

I also learned (after doing some research on the web), that the original
metal 6L6 tubes, did not have the same power output as the glass
version. I NEVER KNEW THERE WAS A DIFFERENCE IN THE
CHARACTERISTICS I thought they were the same tube in a different
container.

*** And this explains something that occurred 40 some years ago. When I
was running my tube power amps for my stereo, (four 6L6GC tubes
Push-Pull Parallel, in each mono block amp), one of the tubes went bad.
I went to my box of used tubes and found a 6L6 metal case, and used that
for a temporary replacement. Although that tube tested GOOD, the amp
just did not sound or perform properly. It did work, but lacked a lot of
the "punch" it had before. A few days later I bought a new 6L6GC, and
the amp worked great once again.

Now, 40 some years later, I learned why that metal 6L6 did not work
properly !!!!

I also learned in recent times that for best performance, a pair or quad
of output tubes should be MATCHED. Back then, I never knew anything
about matching. If it was the proper numbered tube, and a tube that
tested good, I'd just plug it in and GO....

The short answer is that most of the tubes will put out the same power
at audio as they will at RF. Not counting some specific tubes such as
the microwave tubes. Tubes start loosing efficency as the frequency
goes higher into the RF ranges. The common 6146 tube might put out
about 50 watts up to about 50 MHz but will work to 150 MHz but only put
out 30 watts and stay within the ratings.

There is one other thing to look at. That is the class of service.
Running class C will put out the most power but can only be used for
certain types of RF signals due ot the distortion. It can not be used
at all for normal audio amplifiers.

As with the 813 tube, most tubes rated for much over 50 watts output
will often have a plate voltage of over 1000 volts,many like to have
2000 volts or more.

For the best sound the tubes should be matched. They are operated in
what is called a push-pull circuit. Often close to class B. That is
when one tube is putting out power,the other tube isn't during a cycle.
It is at the crossover point that if they are not well matched you get
most of the distortion. Many audio amps often operate more like AB
class to help eliminate that problem. It is not much of a problem at RF
due to the way the output circuit works.

wrote:
"It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down. If you go to 2X 700 volts, it might not be a matter of the tubes, it might be the tubes sockets.


They used a lot of ceramic tube sockets in transmitters.


What does limiting the G2 do ? Keep it from arcing to the suppressor grid ? I have wondered before about why the hell doesn't all this **** just arc and weld itself together. Well, OK I know it has to do with the vacuum, but still.

However wiki reports that permissivity of air at STP is only something like 1.000 point whatever, with 1 being the standard.



--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

On Wed, 1 Mar 2017, Michael A. Terrell wrote:

wrote:
"It all about raising up the plate supply voltage while keeping the screen
supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the
power, but also to try to keep the plate volage down. If you go to 2X 700
volts, it might not be a matter of the tubes, it might be the tubes
sockets.


They used a lot of ceramic tube sockets in transmitters.

ANd the really good tubes had plate caps.

Michael

On Wed, 1 Mar 2017 13:54:34 -0500, Michael Black wrote:

On Wed, 1 Mar 2017, Michael A. Terrell wrote:

wrote:
"It all about raising up the plate supply voltage while keeping the screen
supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the
power, but also to try to keep the plate volage down. If you go to 2X 700
volts, it might not be a matter of the tubes, it might be the tubes
sockets.


They used a lot of ceramic tube sockets in transmitters.

ANd the really good tubes had plate caps.

Michael

I can relate to using ceramic sockets, because the standard ones would
likely burn up from such high voltages.
* What are the standard sockets made out of anyhow????

Considering the closeness of the tube socket pins, I could see where
there could be arcing between pins at voltages that are or exceed 1000V.
Plate caps eliminate that problem. However, I would assume that the wire
going to those plate caps would need to have insulation capable of the
voltage, and where they go thru the chassis, would need grommets that
can handle the voltage too. Not to mention the connections below the
chassis such as terminal strips.

I have not worked with any voltages exceeding 1000V (except the HV in
the old tv sets). But since I am on a farm, I know what an electric
fencer can do. If a fence wire gets too close to a tree (for example),
it will snap and shoot a spark a half inch long, or longer. Most of
those fencers are around 5000 V. Those fence wires are all run on
porcelin insultors. (although there are now plastic ones that work as
well).

I have felt them fences far too many times too..... I have been
literally knocked down from them more than once, if I was well
grounded.... NOT FUN.

Fortunately those fencers do not kill a person or animal (or we would
not use them, since livestock are expensive and dead people are not a
good thing). The voltage is high, but the current is low. (and it
pulses).

Anyhow, while I have not done it, I am sure building transmitters (or
anything else) using those high voltages, require special components and
wiring, which in itself requires special knowledge.

In article ,
says...



I can relate to using ceramic sockets, because the standard ones would
likely burn up from such high voltages.
* What are the standard sockets made out of anyhow????

Considering the closeness of the tube socket pins, I could see where
there could be arcing between pins at voltages that are or exceed 1000V.
Plate caps eliminate that problem. However, I would assume that the wire
going to those plate caps would need to have insulation capable of the
voltage, and where they go thru the chassis, would need grommets that
can handle the voltage too. Not to mention the connections below the
chassis such as terminal strips.

I have not worked with any voltages exceeding 1000V (except the HV in
the old tv sets). But since I am on a farm, I know what an electric
fencer can do. If a fence wire gets too close to a tree (for example),
it will snap and shoot a spark a half inch long, or longer. Most of
those fencers are around 5000 V. Those fence wires are all run on
porcelin insultors. (although there are now plastic ones that work as
well).

I have felt them fences far too many times too..... I have been
literally knocked down from them more than once, if I was well
grounded.... NOT FUN.

Fortunately those fencers do not kill a person or animal (or we would
not use them, since livestock are expensive and dead people are not a
good thing). The voltage is high, but the current is low. (and it
pulses).

Anyhow, while I have not done it, I am sure building transmitters (or
anything else) using those high voltages, require special components and
wiring, which in itself requires special knowledge.

I have 2 amplifiers for my ham radios. Both have about 2700 volts on
the plates of the tubes. The current drawn by the tubes is almost one
amp. I have worked on them several times. To do that I make sure the
capacitors have fully discharged by watching the voltmeter on the amps
go near zero. When I take the cover off, vurey carefully, I then short
the capacitors to ground to make sure the volt meter is not giving a
false reading. The voltage and current is not like a fence charger. It
will dump a lot of current into you and often kill. Fence chargers are
more like a static electricity shock, lots of voltage,but little
current. They are made to shock and not to kill.

It does take some special insulated wire for the amps and other high
voltage items. Most common wires are insulated for around 600 volts or
even 300 volts. That 2700 volts will often burn through wire insulated
like that . Only 'good' thing about it,is that it will not jump much of
an air gap. However with RF applied the operaing voltages inside the
amp is somewhat greater and can arc a short distance.

Most of the tubes operate with less than 500 volts on the pins with the
higher voltage going to the cap on the plates. Ceramic is often used
because of the heat on the pins of the tubes. The filiments get hot and
direct transfer heat, and the heat of the plate is radiated to some
extent. Afer all, if an amp is putting out 1000 watts it is using close
to 1500 to 2000 watts to do it. That is almost as much as some of the
smaller 'bathroom' portable electric heaters put out.

wrote:

"It all about raising up the plate supply voltage while keeping the
screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down.

** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power.


If you go to 2X 700 volts, it might not be a matter of the tubes,
it might be the tubes sockets.


** Most sockets can handle the extra voltage.

What does limiting the G2 do ?


** Keeps the screen current within limits.

Having the screens glowing bright is the biggest killer of power tubes.


..... Phil

"** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power. "

I think you got this ****ed up somehow. When the load impedance is halved then the power is doubled. I'll put it down as a typing error unless you argue the point.

What's more, double the voltage into the same load if four times the power, not two.

"Having the screens glowing bright is the biggest killer of power tubes."

Perhaps you are older and thus have more knowledge then I on some of this. From what I understood from the old days, tubes (valves) generally break down due to the cathode nit being able to put out current, and that is where all the current comes from.

However of course there can be other failure modes. Are you saying that some sort of arc or leakage is damaging the valve ? If so I would like your explanation of this failure mode.

On 02/03/17 14:38, wrote:
"** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power. "

I think you got this ****ed up somehow. When the load impedance is halved then the power is doubled.

Phil meant "double the load impedance". Not half.
If you do that and double the voltage, current is the same,
so power is only doubled.

Clifford Heath.

wrote:

"** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power.

I think you got this ****ed up somehow.


** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I



"Having the screens glowing bright is the biggest killer of power tubes."


Perhaps you are older and thus have more knowledge then I on some of
this. From what I understood from the old days, tubes (valves)
generally break down due to the cathode nit being able to put out
current, and that is where all the current comes from.

However of course there can be other failure modes. Are you saying
that some sort of arc or leakage is damaging the valve ?


** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded.

Then guess what happens ??

If the screen supply voltage is too high, it take excessive current whenever the plate voltage swings low under load.

Data sheets reveal this as an increase in AVERAGE screen current at max signal.

Screen dissipation = V x I average.



..... Phil

On Wed, 1 Mar 2017 15:36:39 -0500, Ralph Mowery
wrote:

false reading. The voltage and current is not like a fence charger. It
will dump a lot of current into you and often kill. Fence chargers are
more like a static electricity shock, lots of voltage,but little
current. They are made to shock and not to kill.

It does take some special insulated wire for the amps and other high
voltage items. Most common wires are insulated for around 600 volts or
even 300 volts. That 2700 volts will often burn through wire insulated
like that . Only 'good' thing about it,is that it will not jump much of

Long ago, I once rook some common #14 wire used for home wiring, to jump
my electric fence across to another pasture. My intent was to use
insulated wire so no one would get shocked. (There were no animals
there, so live wires were not needed.)

I quickly learned that the insulation on those wires (rated at 600V), is
useless against the 5000V of that fencer. I touched that insulation and
got jolted as bad as if I had touched bare wire.

After that, I bought the special insulated wire made for electric fences
that is made for even direct burial. That stuff is costly, but it works.

" ** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I "

Fine, but I don't know why you expressed it that way. There is still a limit to how much voltage you can have. Generally, output tubes are not in series, they are in parallel. As such the impedance into which they work (determined by the transformer of course)must be decreased to realize any increase in power output.

"** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded.

Then guess what happens ?? "

It becomes a triode ? LOL. Not really because the suppressor grid is still in the way.

"If the screen supply voltage is too high, it take excessive current whenever the plate voltage swings low under load. "

This is one of the things I have trouble grasping when it comes to tube technology. I am younger than you and tubes existed only at the beginning of my career. I adapted to solid state quickly and made a profit...

I wonder some things, like when the plate voltage goes lower than the screen voltage. Are you saying that the current flows from the screen grid to the plate ? Or is it pulling from the cathode ? I'd guess cathode but that is just a guess.

There are a few other things about tubes of which I lack knowledge, but I am only 56 and this is 2017. Like the suppresor grid, how the hell did they even find out they needed that ? I mean, some guys in white lab coats looking at a (probably Tektronix) scope saying "There are electrons bouncing back from the plate, we can improve this tetrode by adding another grid". How the hell did they figure that out ?

On Thursday, March 2, 2017 at 2:35:02 PM UTC-5, wrote:
" ** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I "

Fine, but I don't know why you expressed it that way. There is still a limit to how much voltage you can have. Generally, output tubes are not in series, they are in parallel. As such the impedance into which they work (determined by the transformer of course)must be decreased to realize any increase in power output.

"** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded..

Then guess what happens ?? "

It becomes a triode ? LOL. Not really because the suppressor grid is still in the way.

"If the screen supply voltage is too high, it take excessive current whenever the plate voltage swings low under load. "

This is one of the things I have trouble grasping when it comes to tube technology. I am younger than you and tubes existed only at the beginning of my career. I adapted to solid state quickly and made a profit...

I wonder some things, like when the plate voltage goes lower than the screen voltage. Are you saying that the current flows from the screen grid to the plate ? Or is it pulling from the cathode ? I'd guess cathode but that is just a guess.

There are a few other things about tubes of which I lack knowledge, but I am only 56 and this is 2017. Like the suppresor grid, how the hell did they even find out they needed that ? I mean, some guys in white lab coats looking at a (probably Tektronix) scope saying "There are electrons bouncing back from the plate, we can improve this tetrode by adding another grid". How the hell did they figure that out ?

I think a lot of refinements are trial and error, or just plain dumb luck. Maybe some hack was assembling the plate structure and left some support wires in place instead of cutting them before stuffing the assy in the bottle and sealing the glass. Make connections to the wrong wires and..

It's the guys like Tesla who could envision things like polyphase AC before anyone else that impress the beejeezus out of me. Edison was a trial and error guy while Tesla was reading blueprints from inside his skull.

wrote:
" ** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I "

Fine, but I don't know why you expressed it that way.


** You snipped the crucial line.

Looks like you NEVER read it.


There is still a limit to how much voltage you can have.


** Its about 2.5kV for a 6L6GC.

Generally, output tubes are not in series,

** Massive red herring.


"** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded.

Then guess what happens ?? "

It becomes a triode ?


** FFS the wire melts, bits come off and create shorts.




..... Phil

"IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I "

I had that down before I had pubic hair. The way you worded it was the subject of my comment.

"** Its about 2.5kV for a 6L6GC. "

According to http://www.radiostation.ru/tubes/6L6GC-GE.pdf you are really pushing it. But then IIRC, that plate voltage is at quiescence and can go double. They were not rated like transistors. A transistor might say "1,000 volts" and at 1,175.3 volts it shorts out. Seems like they EXPECTED alot of voltage on tubes.

However there are limits on other components of course, and an audio circuit is not quite like an LOPT. (actually that is closer to the OP than our digression, but then this is SER so that is expected) But to bring up the LOPT, or HOT over here, that does operate in class C. Most RF outputs of course operate in class C. That is a whole different world.

Plate dissipation doesn't mean ****, it is just a matter of peak current and peak voltage, which when they don't happen at the same time are of course much easier to deal with.

"** FFS the wire melts, bits come off and create shorts. "

I am in the "WTF was I thinking" mode now. At my young age, I guess I could say I have forgotten more about electronics than many know. That is one of the most simple concepts but yet it slipped my mind. Of course when the wires melt they go out of whack and cause problems. I got too used to transistors. You can talk about some layer in a MOSFET breaking down and causing some weird leakage or some ****, but this is mechanical. The real problem is I must be losing it because I am from a car family.

Really, I have out-trouble shot the factory guys and I can give you two examples. One was the "bulletproof" 2.5 L that ran like ****. The books all said it had timing gears and therefore would not jump time. Therefore the crank sensor was what the book said. But after I saw the **** blowing back through the throttle body I said "Tear down for timing chain", a part that the DEALERSHIP said it did not have. I was right. The dealership, after the guy paid the diagnostic said "replace engine". Instead my buddy got off with a hundred bucks ort whatever for timing irons.

Another notable thing was my ex-lawyer's pickenup truck. (he got disbarred, go figure) It was some sort of Datsun or something but he wanted to keep it. Now this guy was no dumbass, as a matter of fact he pretty much built his own house. Ad he was not dumb when it came to cars either but this had him stumped.

The problem was that at random intervals it would run like ****, and I mean not be able to get out of its own way run like ****.

The problem we traced down was about a Woodruff key i n the crankshaft. He had had the timing belt replaced not long before and apparently (and a machinist verified this) that apparently the mechanic who did the job lost the original Woodruff key which was metric.

Well he could not get a metric one so put in a USian replacement, which was loose. Over a short time it sheared because it was direct from the crank to the damper. This system also ran the camshaft. So every once in a while it went out of phase. It DID take some doing to figure that one out but the guy had no problem with money.

The reason he wanted specifically to keep this little pickup truck had to do with the suspension. (he was smart enough for that) He had a tow bar on the front and used to tow it with his camper. He said that was the only vehicle he could find that could be easily backed up, like a trailer. After I got more information on the vehicle I thinki I found out why.

It had linear torsion bar suspension. Unlike those old Dodges that had crossbar suspension, (which really wasn't all that bad) cars like the Caddilac Eldoado and the Olds Toronado had the torsion bars going front to back. They had special rims and if you look at the book they were set to (or could be) zero toe in, zero caster, zero camber.

He told me that this was the only thing he could tow that he could back up with. All other vehicles jacknifed. Start backing up and the steering wheel would go all the way one direction or the other. Not this one. Linear torsion bar suspension.

And it was a ****can. My Toronados had that suspension but they were suspending a 455 with almost 500 horsepower. This was four cylinder ! But he liked it so we fixed it.

By the time we got to it, the Woodruff key had worn the notch in the crank so badly that a new one would not be tight either, so we brazed it in.

Sorry to be so long but then, this is Usenet. Bottom line, if anyone thinks I'm stupid, I want know what you think of the rest of the people. I mean like that broad on the video whose boyfriend asks here "If you are doing 60 miles per hour and drive for an hour, how far have you gone ?". And she could not answer it. In fact I think some asshole somewhere called that video politically incorrect.

God damn.

wrote:


Power = V x I "

I had that down before I had pubic hair. The way you worded it was
the subject of my comment.

** You did not READ what I wrote at all

- you bull****ting, over-snipping ****head.



"** Its about 2.5kV for a 6L6GC. "


According to http://www.radiostation.ru/tubes/6L6GC-GE.pdf



** Fraid that ref does not mention the spec.

You bull****ting ****ing idiot.



Plate dissipation doesn't mean ****,


** No, YOU don't mean **** .

Cos you are a piece of it.




I am in the "WTF was I thinking" mode now.



** Good, stay there for the rest of your miserable ife.


Wot a PITA ****ing moron ......



..... Phil

"** Fraid that ref does not mention the spec.

You bull****ting ****ing idiot. "

Bull****, it says 500 ****ing volts. Now who cannot read ?

Let's go ahead and **** up Usenet with a flame war ey ?

And you will lose.

wrote:


"** Fraid that ref does not mention the spec.

You bull****ting ****ing idiot. "

Bull****, it says 500 ****ing volts.


** Wrong spec - you bull****ting imbecile.

In most tube books, "plate volts" = "plate supply" voltage !!!

The **actual plate voltage** swings up to nearly double in operation, single ended or push pull. The 2.4kV figure I posted is the max, zero current plate voltage that is guaranteed. IOW, the insulation rating.

In an operating push-pull stage, plate voltage reaches max on a tube when plate the current is near zero. The opposite is true too, plate voltage reaches minimum when plate current is max on that tube.

EL34s are *speced* to operate with a 750V supply, so the pate voltage on one EL34 in a PP pair is nearly 1500V when the voltage on the other is less than 60V.

All I am saying is that 6L6s can do the same and commercial examples exist that prove the point.

You know absolutely NOTHING about tube output stages.

FYI:

Don't fret too hard, hardly anyone does.



..... Phil

"The **actual plate voltage** swings up to nearly double in operation, single ended or push pull. The 2.4kV figure I posted is the max, zero current plate voltage that is guaranteed. IOW, the insulation rating. "

I am not exactly sure what you're saying here. Are you saying that tubes such as this are rated in such a way are expected to operate at twice their "max" rating ?

I never got into tubes all that much, when was getting into the field it was going solid state and I was adapting to it.

"You know absolutely NOTHING about tube output stages."

You're pretty friendly today, did you find a good pot dealer or something ?

"Don't fret too hard, hardly anyone does. "

How come so kind ?

But actually tubes are a bit harder to understand than like transistors etc.. Take your transconduct and and mu and sll of that and give me hfe and HFE..

But that's just one Man's opinion. If you can counter with an argument that tubes are better, bring it on.

Don't fret too hard, hardly anyone does."

I was working in the music industry. These MFs got where they have dual purpose valve sockets and via a micrprocessor will adjust the bias for you. I mean they got sockets that will take a KT88 or a 6BQ5. I am not fretting but I am considering a career in flipping burgers. It is getting that bad, to the point where I quit my job.

Next.

wrote:

"The **actual plate voltage** swings up to nearly double in operation, single ended or push pull. The 2.4kV figure I posted is the max, zero current plate voltage that is guaranteed. IOW, the insulation rating. "

I am not exactly sure what you're saying here. Are you saying that tubes such as this are rated in such a way are expected to operate at twice their "max" rating ?


** What I am saying is simple:

The only *plate voltage limit* on a power tube is the breakdown voltage of the insulation.

The usual weak spot is between pins 2 and 3, the heater and the plate of many audio power tubes. Having a plate connection on top of a tube instead helps a lot.

The other limits are with max cathode current and max dissipation of the plate structures or screen grids.


...... Phil

"Having a plate connection on top of a tube instead helps a lot. "

It sure did with HOPs (LOPT for you all across the pond)

But IIRC in the beginning they used that top connector for the grid. Seems that later they figured out a better way.

On Thursday, March 9, 2017 at 4:51:22 AM UTC-5, wrote:
"Having a plate connection on top of a tube instead helps a lot. "

It sure did with HOPs (LOPT for you all across the pond)

But IIRC in the beginning they used that top connector for the grid. Seems that later they figured out a better way.

LOL! I remember when I was just getting started in TV repair and my dad had a 40s radio in the shop for repair. In horror, I saw him put his finger on the "plate" cap of the IF tubes as a poor man's signal tracer. Of course, my first experience with a true plate cap was my finger on a horizontal output tube..

"LOL! I remember when I was just getting started in TV repair and my dad had a 40s radio in the shop for repair. In horror, I saw him put his finger on the "plate" cap of the IF tubes as a poor man's signal tracer. Of course, my first experience with a true plate cap was my finger on a horizontal output tube.. "

I bet you learned some respect for eletricity.

For me it was the cathode of a damper tube, which has even more. That SOB burned my finger all the way to the bone, and cauterised it at the same time.. The "one hand" rule did not save me from that, but really if I completed a circuit to anythihg at the time I could have been history, way back then. Actually that does not sound so bad these days, but that is not the point. Youngers who want nto this business need to know that there are more than five volts in the world.

On Monday, March 13, 2017 at 3:40:12 AM UTC-4, wrote:
"LOL! I remember when I was just getting started in TV repair and my dad had a 40s radio in the shop for repair. In horror, I saw him put his finger on the "plate" cap of the IF tubes as a poor man's signal tracer. Of course, my first experience with a true plate cap was my finger on a horizontal output tube.. "

I bet you learned some respect for eletricity.

For me it was the cathode of a damper tube, which has even more. That SOB burned my finger all the way to the bone, and cauterised it at the same time.

Anybody who does not believe the above should try it themselves. It's happened to me several times - and boy, do those pinpoint burns hurt for days.

On Monday, March 13, 2017 at 3:40:12 AM UTC-4, wrote:
"LOL! I remember when I was just getting started in TV repair
and my dad had a 40s radio in the shop for repair. In horror,
I saw him put his finger on the "plate" cap of the IF tubes as
a poor man's signal tracer. Of course, my first experience with
a true plate cap was my finger on a horizontal output tube..

I bet you learned some respect for eletricity.

For me it was the cathode of a damper tube, which has even more.
That SOB burned my finger all the way to the bone, and cauterised
it at the same time. The "one hand" rule did not save me from
that, but really if I completed a circuit to anythihg at the time
I could have been history, way back then. Actually that does not
sound so bad these days, but that is not the point. Youngers who
want nto this business need to know that there are more than five
volts in the world.

They need 4 or 5 years of union electrical school. It sure helped me.

"They need 4 or 5 years of union electrical school. It sure helped me"

They don't deal with the kind of voltages we had in the old days. Working on a cellphone is not dangerous like an old tube type color TV. (or B&W for that matter) Things had hot chassis, 5 KV going to the flyback and yoke and all kinds of fun stuff. Alot of stuff runs on a walwart now that removes most of the danger.

I learned respect for electricity at a very young age. My Uncle gave me the airforce primer on it and I read every word. I also learned the hard way at times, but rarely. I also remember that when the print says "DO NOT MEASURE" they mean it, for a couple of reasons. Some things are just too much voltage, other things are sensitive to the load and might fry. I used to get the scope probe just near a horizontal output tube and be able to tell if it is running right. I had a procedure down pat, I almost always knew what was wrong within five minutes, most times in less than a minute.

The damper tube incident was because I kinda slipped or something, I knew damnwell to stay away from that thing.

I also did some electrical work and have seen some things... Shared neutrals for example. I have done older houses where the last guy misidentified the neutral and caused a shock hazard. I had to correct this ****. Nobody else seemed to be able around here.

wrote:
On Monday, March 13, 2017 at 3:40:12 AM UTC-4, wrote:
"LOL! I remember when I was just getting started in TV repair
and my dad had a 40s radio in the shop for repair. In horror,
I saw him put his finger on the "plate" cap of the IF tubes as
a poor man's signal tracer. Of course, my first experience with
a true plate cap was my finger on a horizontal output tube..

I bet you learned some respect for eletricity.

For me it was the cathode of a damper tube, which has even more.
That SOB burned my finger all the way to the bone, and cauterised
it at the same time. The "one hand" rule did not save me from
that, but really if I completed a circuit to anythihg at the time
I could have been history, way back then. Actually that does not
sound so bad these days, but that is not the point. Youngers who
want nto this business need to know that there are more than five
volts in the world.

They need 4 or 5 years of union electrical school. It sure helped me.


Did it teach you how to wire the HV power supply in a high power TV
transmitter? Have you ever worked with 10 KV shielded cable? Years ago I
was installing a TV transmitter when the local building inspector told
me that I had to hire a local wire monkey. There was no one in tea area
that did industrial level work, so I showed him the HV cable and asked
which of the GOBs was bonded and insured for $1 million to cover any
damage to the equipment.

I showed him the table covered with the factory installation and
asked him to read the top left corner where it said "Electrician,
connect power here". All of the switchgear was bolted to a 4'x10' sheet
of 1/4" steel plate. He insisted that it had to be taken out and screwed
to a sheet of 1/2" plywood. There was over a ton of transformers and
switches that would have snapped plywood into pieces. He was not
qualified to inspect anything bigger that a small store or one of the
thousands of Condos in the area. He had no idea who the FCC was, or what
a FCC Construction Permit was. He was as clueless about the FAA permit
for the tower or the lighting requirements.

Then I handed him my copy of the NEC and asked him to show me the
relevant sections for industrial and studio wiring. He tossed it on the
table, cursed me out and said he would be right back with a 'Cease and
Desist Order to stop work on the new TV station. He never came back.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

Michael Terrell wrote:
wrote:
On Monday, March 13, 2017 at 3:40:12 AM UTC-4, wrote:
"LOL! I remember when I was just getting started in TV repair
and my dad had a 40s radio in the shop for repair. In horror,
I saw him put his finger on the "plate" cap of the IF tubes as
a poor man's signal tracer. Of course, my first experience with
a true plate cap was my finger on a horizontal output tube..

I bet you learned some respect for eletricity.

For me it was the cathode of a damper tube, which has even more.
That SOB burned my finger all the way to the bone, and cauterised
it at the same time. The "one hand" rule did not save me from
that, but really if I completed a circuit to anythihg at the time
I could have been history, way back then. Actually that does not
sound so bad these days, but that is not the point. Youngers who
want nto this business need to know that there are more than five
volts in the world.

They need 4 or 5 years of union electrical school. It sure helped me.


Did it teach you how to wire the HV power supply in a
high power TV
transmitter? Have you ever worked with 10 KV shielded cable?

No, no. I've mostly just driven around a van or truck with supplies here and there. I have wired up one or two places behind walls, roughed-in a few panels, outlets, etc.. and finished them, maybe. But, no. I haven't recently gone into radios, TVs or anything else and bothered anything.

"Did it teach you how to wire the HV power supply in a high power TV
transmitter?"

No

"Have you ever worked with 10 KV shielded cable?"

Years ago, but not handling any real current.

"He was not
qualified to inspect anything bigger that a small store or one of the
thousands of Condos in the area. He had no idea who the FCC was, or what
a FCC Construction Permit was. He was as clueless about the FAA permit
for the tower or the lighting requirements. "

Not surprising. Inspectors do not make what the people who do the real work make, I have found out why many times in the building trades. (but not transmitters)

"...cursed me out and said he would be right back with a 'Cease and
Desist Order to stop work on the new TV station. He never came back. "

Probably a rookie. Really. they give these guys authority without proper testing and vetting. That is the way i t works in this country and I am sure you are not all too happy about it either.

Know what else ? On a plumbing job I refuse to use teflon tape. I have personally proven it to be inferior to not only pipe dope, but even regular hand soap.

Someone lobbied for these regulations, just like any other. Government is deaf dumb and blind. they cannot do anything and that is why they are in government jobs.

There are exceptions but they are, of course exceptions. One was a very competent electrical inspector, they gave him the name "Ivan the terrible" because he really did his job. My work satisfied him even though I did not go through all the apprenticeship and all that, I learned from family. Most contractors dreaded his arrival to a job to inspect. And I have seen their work and some of it was downright dangerous. Other inspectors looked the other way but not Ivan Cucic. (the terrible) He did not want to see kids getting burnt in their beds n **** and I agree.

If you do something wrong like in electrical wiring, which is relatively simple, and it causes death or injury, you belong in jail. You should see how it is here. Licensed, bonded and insured mean nothing, all they do is pay off if you **** up. I want it not ****ed up. I never pursued that because I sold the job as "If I **** up and your house burns down I lose my house, if the licensed, bonded and insured people **** up an insurance people pay off. Who has the greater incentive to do the job right ? But I was never afraid of an inspection in fact I welcomed it.

I have seen things that will put hair on your chest, curl it and take it off in one fell swoop. Maybe we need a thread about that. And industrial too, why do they allow shared neutrals in commercial buildings ? And the reason that the shower goes hot when someone flushes a toilet is because it was not plumbed right, IMO. You have to not use the easiest method to avoid that.. You take the toilet supply right off the main, way before it gets to the hot water tank. But they do not do that because it costs more money. So if you get scalded it is not their problem and if it is, they are licensed, bonded and insured so they suffer no loss.

And believe me, that is prevalent here. I have pulled extension cords out of walls.