In article , Hagstar wrote:

It's 50 bucks- likely it's an emission tester. These are much more
useful than, say, a TV7 because you can own it now and not have to save
money for years. If a person would like to use a Hickok but never buys
one and has to guess as to tubes, how are they ahead of the game? I'm
absolutely certain many of you would say it's MUCH better that they
NEVER buy a tester their entire lives if they can't afford a high end
Hickok. Yeah, everything else is a toy, uh huh- and the TV7 doesn't even
give a direct reading IIRC but requires math each time !

Actually, some of the cheap Hickok units are real transconductance testers,
and some of them do show up for next to nothing now and then. They aren't
any TV7, but they sure beat out the drugstore testers.

Some of the emission testers are no better than drugstore testers, and they
have a tendency to indicate perfectly good tubes are bad, or vice-versa.
This can be extremely frustrating if you ask me. They'll find open filaments
and poor emission, but other problems (especially on beam power tubes) do
not show up on them.

When you're paying some of the bloody insane prices on power tubes thes
days, a good tube tester can pay for itself in short order in the tubes
you don't throw out even though they are fine, and in the tubes you don't
have to keep around for substition testing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article ,
says...



IIRC, the Knight 600B is an emission type tester.

73, Leo

Yes... and the reason I pointed this one out had to do with the
comments about Radio Collectors.... that do NOT have any test equipment
and expect to restore radios... although it isn't a Hickok ...

it IS more than adequate for testing old tubes for old radios ... in
many ways it is better because it is both cheaper and easier to use...

I have an old junker Paco that I use ........ about 90% of the time
I check tubes... the Hickok sets in the corner along with the
MU-160 Sencore... both have their special uses.. but for the everyday
fixing up of these old radios.. the KnightKit or Cheap HeathKit
Paco whatever is fine!... trying to help the Newbies that don't have
equipment to get some that works and is reasonably priced!

John k9uwa

In article ,
says...



IIRC, the Knight 600B is an emission type tester.

73, Leo

Yes... and the reason I pointed this one out had to do with the
comments about Radio Collectors.... that do NOT have any test equipment
and expect to restore radios... although it isn't a Hickok ...

it IS more than adequate for testing old tubes for old radios ... in
many ways it is better because it is both cheaper and easier to use...

I have an old junker Paco that I use ........ about 90% of the time
I check tubes... the Hickok sets in the corner along with the
MU-160 Sencore... both have their special uses.. but for the everyday
fixing up of these old radios.. the KnightKit or Cheap HeathKit
Paco whatever is fine!... trying to help the Newbies that don't have
equipment to get some that works and is reasonably priced!

John k9uwa

In article , (Scott Dorsey)
writes:

Actually, some of the cheap Hickok units are real transconductance testers,
and some of them do show up for next to nothing now and then. They aren't
any TV7, but they sure beat out the drugstore testers.

Some of the emission testers are no better than drugstore testers, and they
have a tendency to indicate perfectly good tubes are bad, or vice-versa.
This can be extremely frustrating if you ask me. They'll find open filaments
and poor emission, but other problems (especially on beam power tubes) do
not show up on them.

Can someone explain how a tube can show good cathode emission, but not be up to
snuff in transconductance? A tube's performance depends on teh geometry and
structure of its grids and plate and their spacing. If hte tube hasn't been
physically knocked around, the geometry hasn't changed. So if the cathode is
putting out the electroncs, how can the tube not be up to snuff?

I know about grid emission and cathode interface.
BTW, I have a vintage 1928 Hickok that is indeed a mutual conductance tester.
It "does the math" with a two-coil meter movement.
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , (Scott Dorsey)
writes:

Actually, some of the cheap Hickok units are real transconductance testers,
and some of them do show up for next to nothing now and then. They aren't
any TV7, but they sure beat out the drugstore testers.

Some of the emission testers are no better than drugstore testers, and they
have a tendency to indicate perfectly good tubes are bad, or vice-versa.
This can be extremely frustrating if you ask me. They'll find open filaments
and poor emission, but other problems (especially on beam power tubes) do
not show up on them.

Can someone explain how a tube can show good cathode emission, but not be up to
snuff in transconductance? A tube's performance depends on teh geometry and
structure of its grids and plate and their spacing. If hte tube hasn't been
physically knocked around, the geometry hasn't changed. So if the cathode is
putting out the electroncs, how can the tube not be up to snuff?

I know about grid emission and cathode interface.
BTW, I have a vintage 1928 Hickok that is indeed a mutual conductance tester.
It "does the math" with a two-coil meter movement.
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

Mike Knudsen wrote:

Can someone explain how a tube can show good cathode emission, but not be up to
snuff in transconductance? A tube's performance depends on teh geometry and
structure of its grids and plate and their spacing. If hte tube hasn't been
physically knocked around, the geometry hasn't changed. So if the cathode is
putting out the electroncs, how can the tube not be up to snuff?

Let's say you have a beam power tube that was used on an amplifier with
a screen grid supply problem, and the screen grid drew current and burned
completely away. There's nothing left any more.

That tube will test just fine on an emission tester. The cathode is putting
out plenty of electrons, but the tube Gm and mu are way off because the
geometry itself has been radically altered. It tests fine, but it will
not even come close to working in a circuit.

Okay, it's an extreme example, but plenty of things go wrong with tubes
other than the cathode getting stripped.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Mike Knudsen wrote:

Can someone explain how a tube can show good cathode emission, but not be up to
snuff in transconductance? A tube's performance depends on teh geometry and
structure of its grids and plate and their spacing. If hte tube hasn't been
physically knocked around, the geometry hasn't changed. So if the cathode is
putting out the electroncs, how can the tube not be up to snuff?

Let's say you have a beam power tube that was used on an amplifier with
a screen grid supply problem, and the screen grid drew current and burned
completely away. There's nothing left any more.

That tube will test just fine on an emission tester. The cathode is putting
out plenty of electrons, but the tube Gm and mu are way off because the
geometry itself has been radically altered. It tests fine, but it will
not even come close to working in a circuit.

Okay, it's an extreme example, but plenty of things go wrong with tubes
other than the cathode getting stripped.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , (Scott Dorsey)
writes:

Let's say you have a beam power tube that was used on an amplifier with
a screen grid supply problem, and the screen grid drew current and burned
completely away. There's nothing left any more.

Agreed. Worse yet, a 6146 that got overdriven and the control grid has bruned
away. No gain at all, but good emission.

But I did ask "other than physical abuse", and maybe "electrical abuse" should
have been included as well. Is it possible for a non-abused (in any way) tube
to lose gain and performance, while its emission remains good?

Not including gas, which I believe the cheap tube testers can catch.

BTW, I once owned a little grid emission tester, whihc I have seen mentioned
here once or twice. Grid emission will kill your AGC line. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , (Scott Dorsey)
writes:

Let's say you have a beam power tube that was used on an amplifier with
a screen grid supply problem, and the screen grid drew current and burned
completely away. There's nothing left any more.

Agreed. Worse yet, a 6146 that got overdriven and the control grid has bruned
away. No gain at all, but good emission.

But I did ask "other than physical abuse", and maybe "electrical abuse" should
have been included as well. Is it possible for a non-abused (in any way) tube
to lose gain and performance, while its emission remains good?

Not including gas, which I believe the cheap tube testers can catch.

BTW, I once owned a little grid emission tester, whihc I have seen mentioned
here once or twice. Grid emission will kill your AGC line. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

Mike Knudsen wrote:
In article , (Scott Dorsey)
writes:

Let's say you have a beam power tube that was used on an amplifier with
a screen grid supply problem, and the screen grid drew current and burned
completely away. There's nothing left any more.

Agreed. Worse yet, a 6146 that got overdriven and the control grid has bruned
away. No gain at all, but good emission.

But I did ask "other than physical abuse", and maybe "electrical abuse" should
have been included as well. Is it possible for a non-abused (in any way) tube
to lose gain and performance, while its emission remains good?

Sure, because you can get less dramatic examples of that sort of thing.
Grids that sag a little bit, for instance. Yes, it's a mechanical failure,
but it's a common one and it's not necessarily due to abuse. Deformed plates
on power tubes are common too.

Not including gas, which I believe the cheap tube testers can catch.

Yes.

BTW, I once owned a little grid emission tester, whihc I have seen mentioned
here once or twice. Grid emission will kill your AGC line. --Mike K.

Somewhere I have a free tube tester that Chicago Transformer gave me as a
promotional item. It puts the tube filament across the AC line, with a
neon bulb and resistor in series. If the filament is good, the neon bulb
lights up, and the lamp doesn't pass enough current to light up, let alone
damage, the filament. Totally useless, but a nifty conversation piece.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."