6AU6 Plate to Grid short

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

 

On Tuesday, November 29, 2016 at 7:11:58 AM UTC-5, febru...@nonewhere.com wrote:

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

The short answer is NO. 6UA6 tubes are still available in the marketplace.

Dan

 

On Tuesday, November 29, 2016 at 7:11:58 AM UTC-5, febru...@nonewhere.com wrote:

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

Before I was forced to try something that drastic I'd redesign it for a transistor. Here is an ebay listing for an NOS tube for $4 including shipping. He has four of them if you want to forestall drilling into your tube for a few decades...

http://www.ebay.com/itm/Philco-6AU6A-Electronic-Vacuum-Tube-Made-In-USA-NOS-/262736599165?hash=item3d2c52587d:g:53YAAOSwal5YEXx7

 

[pfjw@aol.com]

On Tuesday, November 29, 2016 at 7:11:58 AM UTC-5, febru...@nonewhere.com wrote:
>>MUCH Snippage<<

a) Nothing you have 'at home' will create sufficient vacuum for what you propose.
b) Even if you have a source of Barium to replace the original 'getter', you would have to remove the envelope entirely to install it.
c) 6AU6 tubes are common, very common. I have at least a dozen in my tube stash. Our club sells them tested and good in the $2 range.
d) And the chances are very likely unless you are a micro-surgeon, that you will screw something up in the process anyway.

Peter Wieck
Melrose Park, PA

 

[N_Cook]

On 29/11/2016 12:11, february30@nonewhere.com wrote:

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

Have you got a source of caesium for the getter?
C/H "shorts" you can often get a bit more life without "bacon & eggs" by
upping the heater volts on the tester for a few seconds, to compress the
oxide? back a bit. G/A shorts presumably due to thermal bending/failed
spot weld unlikely. If I was going to give it a go I'd try very high
magnetic field and high current through the G/A contact and arrange for
the magnetic force to hopefully bend the relevant bit farther away. So
shit or bust, make a G/A spot-weld or spring apart.
If a structural suport failure , reorientate the valve perhaps

 

[Phil Hobbs]

On 11/29/2016 07:42 AM, N_Cook wrote:

On 29/11/2016 12:11, february30@nonewhere.com wrote:
My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.



Have you got a source of caesium for the getter?
C/H "shorts" you can often get a bit more life without "bacon & eggs" by
upping the heater volts on the tester for a few seconds, to compress the
oxide? back a bit. G/A shorts presumably due to thermal bending/failed
spot weld unlikely. If I was going to give it a go I'd try very high
magnetic field and high current through the G/A contact and arrange for
the magnetic force to hopefully bend the relevant bit farther away. So
shit or bust, make a G/A spot-weld or spring apart.
If a structural suport failure , reorientate the valve perhaps

Aren't the getters usually calcium? Caesium has a high vapour
pressure--it's used in photomultipliers, and its migration is
inconveniently fast even at 20C.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

On 11/29/2016 07:18 AM, dansabrservices@yahoo.com wrote:

On Tuesday, November 29, 2016 at 7:11:58 AM UTC-5, febru...@nonewhere.com wrote:
My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

The short answer is NO. 6UA6 tubes are still available in the marketplace.

Dan

There's a very interesting video tour of Mullard's Blackburn Valve
Factory that explains a lot of stuff like that:

https://www.youtube.com/watch?v=GDvF89Bh27Y

Cheers

Phil Hobbs

 

[analogdial]

Still won't work. You better come up with a plan for fixing the
resistor, too.

 

[tom]

<february30@nonewhere.com> wrote in message
news:93rq3c5m16ell224c3iilp95en2ld3ngpq@4ax.com...

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

Troll score - 3 of 10

Please try to up your game.

 

[analogdial]

Michael Black wrote:

There was one from Europe a few years ago that got a lot of travel.

But in 1964 or 65 there was an article in QST about an Argentinian who wa
making tubes. He was mostly interested in making his own power tubes for
transmitters, so his own design rather than copying well known tubes.

They talk about it in the areas where antique radios are discussed,
there's a certain plateau one has to reach and most aren't up there yet.

What I wonder is if it was "common" in the early days of tubes. People
made all kinds of things, I've read that they'd get some quartz and make
their own crystals even and certainly people made their own paper
capacitors in the early days, so making a tube might not be out of the
norm, so long as someone had the resources. It might perhaps have been
more "common" back then, since tubes were still new, but perhaps not. But
it would be interesting to see if there were articles about making your
own tubes back then.

Getting enough vacuum seems to be a common issue, at least once you have
some success as a glass blower. I haven't seen much about whether people
are making triodes or anything more complicated.

Michael

There was alot of tube bootlegging going on in the early 20s. I'm think
a guy with the specialized equipment to make one tube would be strongly
tempted to make a dozen or hire people and make hundreds or more.

 

[Ralph Mowery]

In article <o1kdt0$h08$1@dont-email.me>, tmiller11147@verizon.net
says...

february30@nonewhere.com> wrote in message
news:93rq3c5m16ell224c3iilp95en2ld3ngpq@4ax.com...
My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.



Troll score - 3 of 10

Please try to up your game.

Iknow this is trolling, but on youtube I ran across a person that was
building small tubes such as this at his house. Very interisting to
watch him do it.
Long time ago and I don't recall the title or where to find it.

 

[Michael Black]

On Tue, 29 Nov 2016, Ralph Mowery wrote:

In article <o1kdt0$h08$1@dont-email.me>, tmiller11147@verizon.net
says...

february30@nonewhere.com> wrote in message
news:93rq3c5m16ell224c3iilp95en2ld3ngpq@4ax.com...
My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.



Troll score - 3 of 10

Please try to up your game.

Iknow this is trolling, but on youtube I ran across a person that was
building small tubes such as this at his house. Very interisting to
watch him do it.
Long time ago and I don't recall the title or where to find it.

There was one from Europe a few years ago that got a lot of travel.

But in 1964 or 65 there was an article in QST about an Argentinian who wa
making tubes. He was mostly interested in making his own power tubes for
transmitters, so his own design rather than copying well known tubes.

They talk about it in the areas where antique radios are discussed,
there's a certain plateau one has to reach and most aren't up there yet.

What I wonder is if it was "common" in the early days of tubes. People
made all kinds of things, I've read that they'd get some quartz and make
their own crystals even and certainly people made their own paper
capacitors in the early days, so making a tube might not be out of the
norm, so long as someone had the resources. It might perhaps have been
more "common" back then, since tubes were still new, but perhaps not. But
it would be interesting to see if there were articles about making your
own tubes back then.

Getting enough vacuum seems to be a common issue, at least once you have
some success as a glass blower. I haven't seen much about whether people
are making triodes or anything more complicated.

Michael

 

[Andy Burns]

Michael Black wrote:

Ralph Mowery wrote:

I know this is trolling, but on youtube I ran across a person that was
building small tubes

There was one from Europe a few years ago that got a lot of travel.

You're probably remembering this one

<https://youtu.be/EzyXMEpq4qw>

> People made all kinds of things

There was a more recent one of someone making larger nixie tubes than
the NOS ones

<https://youtu.be/wxL4ElboiuA>

 

[Look165]

A great number of sites on the Net provide old tubes.

There also exist tube regenerators which can remove short-circuits.

It also works for old CRT tubes.

But it is rather expensive and you have to find a shop which owns one.


february30@nonewhere.com a écrit :

My old tube tester confirmed a short in this 6AU6 tube, which explains
why a resistor fried on it's socket. I know replacement is the best
solution, but old tubes are getting hard to find. I always figured
shorts inside tubes occur because the parts inside are loose. Is it
possible to drill into the glass, and use a pin to align the parts so
they are not shorted, then shoot some epoxy inside to keep these parts
solid, so they cant touch anymore?

Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to
suck out the air, then epoxy the hole shut.

 

>"Iknow this is trolling, but..."

I am not so sure. There are alot of people, especially in the US, who think you can DIY things you simply can't. It is a matter of knowing the process.. At this point I wonder if tubes like a 6AU6 are bombarded like CRTs were.

At one point I thought about trying to build an EMPG but after some research (not posting on a forum) found out it is just about impossible without alot of money and resources. I have come up with alot of ideas that simply were not practical, and the ones that were were either unsaleable or already done and at the very least unpatentable.

Also, some people have no idea how to think things through. Even with an adequate vacuum pump, just how do you get the epoxy on there ? Tubes, before final manufacturing processes have a tube through which the vacuum is pulled ad then that is heated right near the seat of the socket, or other end and in the atmosphere the glass tubing collapses and then you cut it off. I am not sure when the getter is applied.

And the OP's assumption that one of the suspension components broke is a bit off as well. The 6AU6 is a pentode right ? Does it have the suppressor grid internally tied to the cathode ? (most do) If so the short is more likely caused by one of those fine wires simply breaking. They are held in place by mica sheets so any misalignment could only come from traumatic mechanical shock.

now if he has a G1 to plate short then the trauma must have been vertical and just made the whole thing shift down and cause the wires at the bottom going to the actual pins short out. Otherwise the short would read cathode to G2, not plate. Well not necessarily.

An excellent exercise in futility for a Tuesday night. Get off the four bucks and buy the tube and replace the resistor.