813 Tube Repair

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Larry Milliken
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Joined: Fri Feb 14, 2014 7:39 am

813 Tube Repair

Post by Larry Milliken »

Does anyone know what type of cement or glue was used to hold the anode cap in place on a glass power tube? I want to re-affix the cap on an 813 so I can re solder the power lead going into the envelope. The old glue has totally lost its hold. Thanks for any information or suggestions.
alleo
Posts: 27
Joined: Wed May 01, 2013 3:02 pm

Re: 813 Tube Repair

Post by alleo »

google metal to glass bond ,it's a ceramic glue i'd think
Larry Milliken
Posts: 81
Joined: Fri Feb 14, 2014 7:39 am

Re: 813 Tube Repair

Post by Larry Milliken »

Thanks! There are several different types to choose from but the only question is how it will stand up to the heat generated by the tube? I continue looking and I appreciate your input.
alleo
Posts: 27
Joined: Wed May 01, 2013 3:02 pm

Re: 813 Tube Repair

Post by alleo »

one outer thought if the wire is exposed on top the tube remembering clip leads'solder a clip lead on the plate wire ,clip it on the tube wire.
ChuckG
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Re: 813 Tube Repair

Post by ChuckG »

I'm guessing the envelope temperature can hit 400-500 degrees F, which is the upper limit for the "high temp" epoxies. That leaves sodium silicate compounds, which is what I believe the factory used.
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jthorusen
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Re: 813 Tube Repair

Post by jthorusen »

Here is the entire E-mail thread that went by many years ago on this subject. Some highlights are for:

Sauereisen Cement

http://www.sauereisen.com.

Parker Furnace and Retort Cement from Grainger


813's are specifically mentioned on page 11.

If you scroll down far enough, the formulations for mixing several types of cement used by tube manufacturers over the years are to be found.

Here you go:

TubeCements.txt
From K1LKY


From: "russ dworakowski" < >
To: Old Tube Radios < >
Subject: Re: Tube base cement - failure mode
Date: Fri, 13 Sep 2002 01:07:49 -0400
Mime-Version: 1.0
Content-Type: text/plain; format=flowed
Message-ID: < >

Well Chuck, not sure about the cement used, getting old though. A good quick and easy fix is garden variey, liquid super glue. Just squeaze a drop at the junction of the base and the glass. It sets up in seconds, solid as a rock! Russ


From: Chuck Swiger < >
Reply-To:
To: Old Tube Radios < >
Subject: Tube base cement - failure mode
Date: Thu, 12 Sep 2002 08:58:32 -0400

Just a quick quick question - I have a 6V6 with a glass bulb
loose in the base. It tests good, but it has some brown residue
around the junction between the base and bulb, AS IF the
cement had boiled out. Does that happen? Can a tube
get so hot the cement liquifies and leaks or bubbles out?
I've seen evidence of this phenomena with 5R4's (both of which had
open filaments), but have never actually witnessed that theory
in action.

Chuck
kb4new



Date: Fri, 13 Sep 2002 08:19:49 -0500 (CDT)
To: Old Tube Radios < >
From: third Eric < >
Subject: CAUTION! do NOT use super glue!

de N4TGC Eric

Cyano-acrylic (a.k.a. "super") glue does not match the expansion
co-efficient of the glass, which will crack. Been there, done that; ruined
a couple of good tubes. I use high-temperature gasket cement (generally
intended for clothes-dryer gaskets), which remains flexible, and bonds to
both the base and glass without yanking on them. It can be gotten at an
appliance store, and flows down into the joint readily. Only caveat: it's
homely, as it apparently only comes in black or reddish-brown!
There are obviously other glues which work: what is the original?

From: "Rhett T. George" < >
Date: Fri, 13 Sep 2002 11:13:05 -0400 (EDT)
Message-Id: < >
To: Old Tube Radios < >
Subject: tube base cements

- Greetings -

The question of tube base cements was recently asked. Here is what I found
in the reference: Max Knoll, "Materials and Processes of Electron Devices,"
Springer-Verlag, 1959.

Pitch (higher hydrocarbons)
Litharge (5-6 parts litharge, 1 part pure glycerine)
Marble cement (5 parts gypsum and alum. baked, 2-3 parts water)
Graphite-silicate of soda (1 part graphite, 5 parts Kaolin, 5-6 parts
(sodium silicate of soda)
Shellac cement (gypsum or other fillers, shellac diluted in alcohol 1:1)
Thermoplastic cement (marble powder, laccain (novo-lacquers) diluted in
alcohol)
Resol (2 parts calcite, kaolin, or whiting, 1 part resol (Bakelite varnish))
Bakelite cement (75-90% calcite, whiting, 5-10% thermosetting phenolaldehyde
resin (Dow Corning 2103))
[This seems to make 80-100% of the recipe!]
Siemens and Halske (65-70% calcite, whiting, 20-25% silicone resin solute
(H.K. 15, Wacker Chemie), remainder solvent (xylol))

Probably more than anyone wanted to know about keeping tube and base
together. Some of the expressions in Table 7/19 are funny, particularly,
"Working time for shellac - Unlimited (If kept in well-closed containers."
Maybe that should read `shelf life'.

73 Rhett - KE4HIH
Date: Fri, 13 Sep 2002 09:25:12 -0600 (MDT)
From: Richard Loken < >
Subject: Re: CAUTION! do NOT use super glue!
To: Old Tube Radios < >

On Fri, 13 Sep 2002, third Eric wrote:

> both the base and glass without yanking on them. It can be gotten at an
> appliance store, and flows down into the joint readily. Only caveat: it's
> homely, as it apparently only comes in black or reddish-brown!
^^^^^^^^^^^^^

Perfect. Any tube I have looked at was glued with something that was
reddish brown...



At 08:51 AM 9/19/02 -0500, you wrote:
From: third Eric < >
Subject: super-glue subject, cont'd

de N4TGC Eric

Or, making glue from horses beat to death ... Barry Ornitz pointed up the
main reason cyano-acrylic glue won't work well on tube bases and caps: they
need a FILLER glue,


Eric,

I have a large mercuryu vapor rectifier (an 872A) with a loose plate cap.. I also have some loose-capped 811A's for use in Linears. Have you located a suitable glue for this purpose?

This is a long standing question.

Roy

Date: Wed, 25 Sep 2002 21:29:27 -0500 (CDT)
To:
From: third Eric < >
Subject: plate cap glue, part 2

de N4TGC Eric

It was indeed on rcvr tubes that I used the RTV silicone. I
checked it's stated heat resistance, and it claims about 400 deg. F. The
hi-temp variety (the bright red stuff) claims 650 deg. F. What sort of
bulb temp. would an 811A achieve? Don't make me get my acetylene torch
out, now ...
e



From: "Barry L. Ornitz" < >
To: "Roy Morgan" < >
Subject: Re: More on silicones
Date: Wed, 25 Sep 2002 19:56:39 -0400

Roy,

The Permatex "Copper" (red) version can be found in most auto stores.
It is the acetic acid releasing variety of silicone but it should work
well. This is rated to about 400 F and it can go higher for
intermittent use. The Sauereisen Cement may be used for larger
transmitting tubes.

73, Barry WA4VZQ t

----- Original Message -----
From: "Roy Morgan" < >
To: "Barry L. Ornitz" < >
Sent: Wednesday, September 25, 2002 03:04 PM
Subject: More on silicones


> At 08:25 PM 9/21/02 -0500, you wrote:
> ...I have generally used the
> >high temperature silicones for small transmitting tubes and
> >large audio output tubes.
>
>
> Is there a "high temperature" product I might find at the local
hardware
> store or auto store that I can look for specifically?
>
> I have an 872 mercury vapor rectifier and at least one 811A with
loose
> plate caps.
>
> Thanks,
> Roy
>
>

>
From: "Barry L. Ornitz" < >
To: "Roy Morgan" < >
Subject: Re: More on silicones
Date: Tue, 1 Oct 2002 19:05:16 -0400

Hi Roy,

> > The Sauereisen Cement may be used for larger
> >transmitting tubes.
>
> I wonder if a person can make that at home (or at the lab of a
friendly
> physicist here at NIST...) I may have the formula here some where
but I
> don't know.

I looked in my 1946 Lange's Handbook but could not find it. It may
have been published in one of the Chemical Formulary series of books.
Sauereisen makes a number of high temperature cements and coatings.
They have their own website too.

I think most of their products are based on inorganic silicates. You
might try a mixture of magnesium oxide and calcium carbonate with
sodium silicate solution to make a thick paste. This makes a
rock-hard adhesive that is used in some pyrotechnic applications. It
should be good for high temperatures if it is dried thoroughly before
use.

I suspect if you check around the chemistry labs at NIST, someone has
an old can of Sauereisen in the back of some cabinet. It is often
used to cement in thermocouples in high temperature applications.
Thinking of this, it might be available in small lots from Omega who
sells lots of thermocouples and accessories.

I found the following:

http://www.omega.com/Temperature/pdf/OB ... EM_SET.pdf
http://www.omega.com/Temperature/pdf/OB ... IR_SET.pdf

73, Barry WA4VZQ

From: "Barry L. Ornitz" < >
To: Old Tube Radios < >
Subject: Tube Glues Again, Plate Caps
Date: Tue, 1 Oct 2002 19:04:49 -0400

A little while back the group discussed various options for
gluing tubes back into their bases. I mentioned the use of
Sauereisen Cement for gluing on plate caps for high
temperature (transmitting tube) applications. This is an
old laboratory product, seemingly around forever, that most
chemistry labs always seem to have hiding on the back shelf
of a storage cabinet. Actually the Sauereisen Company makes
a number of high temperature cements for different
applications. It is an old company with an excellent reputation.
Check their website for details:
http://www.sauereisen.com.

In an offline conversation with Roy Morgan, K1LKY, he asked
about making something similar. I suggested a high
temperature pyrotechnic adhesive based on magnesium oxide
and calcium carbonate mixed with sodium silicate solution
to form t thick paste.

But then I remembered that Omega sells a number of high
temperature cements to glue and insulate thermocouples in
high temperature applications. Omega sells in small
quantities, and they have a huge assortment of products
related to temperature measurement and other
instrumentation. Looking on their website, I found several
high temperature cements that might be suitable
replacements for the Sauereisen. Note that I have not
tried these, but based on the product specifications, they
might work well too.

http://www.omega.com/Temperature/pdf/OB ... EM_SET.pdf

http://www.omega.com/Temperature/pdf/OB ... IR_SET.pdf

Please read the curing instructions carefully as some of
these products require an extended conditioning period
above 100 C to evaporate out residual water. Also note the
materials computability of these. At least one will not
stick to quartz (and likely not to high temperature
borosilicate glass either).

73, Barry L. Ornitz WA4VZQ

From: "Don Davis" < >
To: Old Tube Radios < >
Subject: Re: Tube Glues Again, Plate Caps
Date: Tue, 1 Oct 2002 23:55:06 -0700

Arghhhh.. Why would you ruin an 841 to run at 30 mHz? There are about
10,000 other better, similar tubes to use. Also, there are a whole bunch of
late WWII surplus tubes that work really well up into the 100 MHz range (and
higher) and look cool to boot! And cheap & plentiful on ebay.

73s

Don AD6PB

Paul says:

> I have some 841 tubes that can be made to work up to 30 mc if their
> bakelite bases can be removed and ceramic bases substituted. I also have
> some old dud tubes with ceramic bases. It's easy to break the dud tubes
and
> get the bases off, but what can be done to get the bases off of the 841's?
> These tubes are NOS and not cheap.
>
> 73,
> Paul, W9MEH


From: "Barry L. Ornitz" < >
To: Old Tube Radios < >
Subject: Re: Tube Glues Again, Plate Caps
Date: Wed, 2 Oct 2002 02:46:55 -0400

Paul Monroe, W9MEH, asked:

> I have some 841 tubes that can be made to work up to 30
> mc if their bakelite bases can be removed and ceramic
> bases substituted. I also have some old dud tubes with
> ceramic bases. It's easy to break the dud tubes and get
> the bases off, but what can be done to get the bases off
> of the 841's? These tubes are NOS and not cheap.

Back on Friday the 13th of September, Rhett George, KE4HIH,
listed some of the more common tube base cements as listed
in Max Knoll's book. This is the same reference I have.
Quoting Rhett's post and adding some comments...


Pitch (higher hydrocarbons)
Very early tubes, not common
Warm with a heat gun to soften or soak in mineral
spirits overnight

Litharge (5-6 parts litharge, 1 part pure glycerine)
This actually cross-links and polymerizes
Popular in the 1930's
Warm with a heat gun to soften
Might also soften if soaked overnight in toluene or
xylene [very flammable, keep well away from heat,
sparks, or flames]

Marble cement (5 parts gypsum and alum. baked, 2-3 parts
water)
Soak overnight in dilute acid like vinegar
Not common

Graphite-silicate of soda (1 part graphite, 5 parts Kaolin,
5-6 parts sodium silicate)
Conductive so would not be used for bases
Soak in warm water overnight

Shellac cement (gypsum or other fillers, shellac diluted in
alcohol 1:1)
Low temperature applications only, seldom used
Soak in denatured alcohol overnight

Thermoplastic cement (marble powder, laccain (novo-
lacquers) diluted in alcohol)
Some novolacs were actually thermosets
Soak in toluene or xylene overnight

Resol (2 parts calcite, kaolin, or whiting, 1 part resol
(Bakelite varnish))
Bakelite cement (75-90% calcite, whiting, 5-10%
thermosetting phenol{form}aldehyde resin (Dow Corning
2103))
[This seems to make 80-100% of the recipe!]
{Likely a typo, should be 25 to 10% resin}
These are quite common and are thermosets
Not likely to be attacked by any chemical commonly
available outside of a lab

Siemens and Halske (65-70% calcite, whiting, 20-25%
silicone resin solute (H.K. 15, Wacker Chemie), remainder
solvent (xylol))
Might possibly be softened in xylene or toluene


The most common base cements are the phenol-formaldehyde
types with lots of cheap filler material. You are not
likely to attack these chemically although dilute acid
might attack some of the filler materials. These resins
cure to be hard and brittle. You might try sliding the
blade of an Exacto-Knife between the tube and base to break
the cement a little at a time.

Unfortunately there is no magic method for doing what Paul
wants. Anything that mechanically breaks the resin bond
has the potential to break the glass too. You might
consider using a Dremel tool with the abrasive wheels to
carefuly cut through the phenolic in a few places, being
careful to not cut so deep as to scratch the glass. This
would let you break smaller pieces of the phenolic away
from the glass. But it is still a risky procedure.

The Dremel tool might let you cut slots between the tube
pins in the phenolic. This would greatly reduce the
interpin capacitance and might let you operate on 10
meters. The data from the Jones Handbook notes these tubes
go to 40 MHz, by the way. Back in the 1930's, a hacksaw
would have been used!

73, Barry L. Ornitz WA4VZQ

Date: Mon, 24 Mar 2003 12:48:24
To:
From: Carl Ratner < >
Subject: GB> Vacuum Tube Repair - Glue Warning

Quite often we find old tubes with loose bases, and then we
use glue of one sort or another to re-attach the base to
the glass. In the January 2003 issue of Antique Radio
Classified there are some warnings about this practice in
the Radio Miscellanea column.

One writer stated that cyanoacrylate glues (Crazy Glue)
should never be used to repair power tubes, rectifers, or
other tubes that become very hot. The reason is that these
glues have a very different coefficient of expansion than
glass, which will cause the glue to act like a glass
cutter. According to the writer, the heated glue will cause
the glass envelope to snap off cleanly at the base!
However, the writer also said that the glue may be used on
small signal tubes or battery tubes that don't become too hot.

Another writer pointed out that cyanoacrylate glues are
conductive, and may run down into the pin area where they
can cause trouble. He suggests using the gel version of the
glue to prevent running, or to hold the tube horizontally
when applying glue, to keep the glue from flowing downward
inside the base.

Does anyone know what kind of glue was used originally by
the tube manufacturers? Apparently it had some special
properties such as resistance to heat, and a coefficient of
expansion similar to that of glass. It probably was
quick-setting too, for efficient use on assembly lines. Is
anything similar still being made? Has anyone tried the
high-temperature silicone sealants sold in automotive
supply stores?

73, Carl Ratner

From: "W1EOF" < >
To: "_LIST:GlowBugs" < >
Subject: GB> Re: Vacuum Tube Repair - Glue Warning -- (Original formula information)
Date: Mon, 24 Mar 2003 16:20:05 -0500

From an earlier email on the TubeCollectosAssciation email list -
73, Mark W1EOF


From: Lud Sibley, 10JAN2000: BASE CEMENT AT RCA
(More'n you ever wanted to know!)

The usual base cement was "No. 6," AKA "C6." The official recipe for this
was:

D3 Durite 7.5 lb.
S15 Shellac 19.5 lb.
R3 Rosin 3.25 lb.
M3 Marble flour 170.0 lb.
A4 Alcohol 9.0 l.
M19 Malachite green 10.0 g.

Makes 200 lb., or enough to base 23,500 Type 50s at 0.0085 lb. each. Basic
recipe is in Standardizing Notice 34C-C-6 ("Confidential") of 12-29-48. No.
6 was used in transmitting tubes too: 814s, 860s, etc., and CRTs (7BP7,
etc.). The bills of material for "modern" tubes (post-'30s) didn't specify
the type of cement, but I've seen no sign of a change up to the end.

The "Durite" was Durite Resin #275, from Stokes & Smith of Philadelphia, not
further defined, bought in 50-lb. pails.

The curing process required a cement temperature of about 150øC. (This, vs.
the blistering temperature of bakelite at about 190øC.) The heating
schedule varied:

CRTs: heat 10 min. cool 1.5 min.
813s: heat 3-« min., cool 1-1/3 min.
8025s: heat 5-« min., cool 1-« min.

The color change in the malachite was considered only a rough indicator of
temperature; it was backed-up with a thermocouple thermometer.

There was a slightly modified cement for top caps, with the same ingredients
but using fine and coarse marble flour.

For use in very large tubes like 207s, where excess heat might crack the
seals, there was a low-temperature cement. It was made of "BR-51 Resinoid"
(bought commercially), acetone, and marble flour. It was for only purely
cylindrical seals, and cured at 50øC.

There's been some talk in restorer circles as to the cured cement being
soluble in toluene, acetone, etc. I haven't had any luck. In the old days,
if the RCA warehouse discovered loose bases, they just fixed them with
shellac.

-LAS-

Magers' book on WECo tubes says they bought their base cement premixed,
adding the malachite and some alcohol. That's consistent with WE's smaller
volume.


From: "Russ WQ3X" < >
To: "COLLINS LIST" < >
Subject: {Collins} Re: Tube caps - NO Super Glue
Date: Wed, 28 May 2003 06:33:15 -0400

OK I'll join the fray -

Here's another way that works on 811s: (This is the secret Relic-Tronics
technique so you can send any royalties to my address in QRZ.com
...Joke... )

1. Unsolder the cap and remove it.
2. Suck out or flick out remaining solder from the small hole in the top of
the cap.
3. Remove crumbling remains of original glue from cap. Clean cap and top of
tube with alcohol.
4. Get some Hi Temp silicone RTV made for auto exhaust manifolds. It is
orange and readily available.
5. Put a thin bead of it around the cap and press the cap into place on the
tube. Careful not to get it all over the wire and make sure the wire goes
thru the hole in the top.
6. Hold cap with thumb and wipe off visible excess RTV. Let dry overnight or
so.
7. Resolder the wire connection so that it is nice and smooth like the
original.

The RTV remains flexible and can withstand the heat easily. You don't have
to worry about differences in the coefficient of expansion as you would with
a hard glue. Works for me.

Russ WQ3X


In July, '04, I bought at Grainger a quart of Parker Furnace and Retort Cement:
Max Temperature 3000 F
Parker product # 312-1345
Cost:$5.41 tax included. Grainger number 5E263

Appears to be made as:
Furnace & Retort Cement (2 Lb.)
by William H. Harvey Company
HOWever, the MSDS from the Grainger web site says:
MANUFACTURER'S NAME: SURE SEAL PRODUCTS
ADDRESS: 1901 W. DIVISION ST.
CHICAGO, IL. 60622

EMERGENCY TELEPHONE NO. 312-278-8150

------------------------------------------------------------------------------
HAZARDOUS COMPONENT(S)
------------------------------------------------------------------------------
AQUEOUS SOLUTION OF ALKALINE
SODIUM SILICATE


Date: Thu, 29 Dec 2005 11:00:36 -0800
To: Old Tube Radios < >
From: Scott Robinson < >
Subject: Re: Tube Cap "Glue"
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

Folks,

The epoxy I use (TAP plastics equal volumes stuff in two cans) remains a little flexible after it sets. I have used it for this purpose a number of times and it hasn't cracked any tubes so far.

/scott

At 7:57 AM -0500 12/29/05, stuck in 50s wrote:
Mike & Scott... I've had epoxy assymetrically 'pull' glass & crack it.
Like an 811A I keep around as a reminder. One where I tried to re-fasten
a loose tube base.

On the 6F7 cap. I find Elmer's Carpenter's Glue does FB if there's enuf
of the pourous original 'brown stuff' left. And solder cap while glue
unset as heat hastens curing a lot.

Like I'm an expert or something

'rm


From: "Dr. Barry L. Ornitz" < >
To: Old Tube Radios < >
Subject: Tube Cap "Glue" [High Temperature Adhesives]
Date: Thu, 29 Dec 2005 21:16:57 -0500

Mike, VE7MMH, asked:

> What's the best "glue" for re-fastening a tube cap to the glass envelope?
> (6F7) The original material looks like the brown stuff that's used to
> cement on tube bases. Soldering will hold it on, but mechanically solid
> would be much preferred.

Several folks have already answered with suggestions, but allow me to add a
little to the knowledge base.

The original tube cap glue is a very cheap thermosetting phenolic-based
mixture. About the only folks using it today are the light bulb
manufacturers, and surprisingly enough, most are located in the countries
that still make vacuum tubes (China, Hungary, Czechoslovakia, Poland, etc.).
This glue is both porous and friable. Instead or worrying about matching
thermal coefficients of expansion, the glue just crumbles a little.

Today a number of materials are available that will work for gluing on a
plate cap. But remember the type of tube and the service temperature is
important. Something that works with a small receiving tube may burn up
when used on a cap for a large transmitting tube.

Epoxy glues will generally work reasonably well for receiving tubes. But
remember the differing coefficients of thermal expansion between the tube
and the epoxy itself. You do _NOT_ want to use a "1-minute" or other fast
curing epoxy here. The fast curing stuff is brittle and very rigid. A
24-hour curing epoxy is much better here. However most conventional epoxies
are only rated to temperatures between 105 to 130 C (221 to 266 F). There
are, however, special epoxies rated to 260 C (500 F).

High temperature silicone rubber adhesives also work quite well for
receiving tubes. Bathtub caulk silicones cannot take the high temperatures.
I suggest GE RTV-106, RTV-116 or RTC-159 which are rated to 260 C (500 F).
All of these are somewhat flexible.

For transmitting tubes, where the plate lead gets quite hot, and may, in
fact, be used to transfer heat to an external radiator, epoxies or silicones
are unsuitable. An old chemical laboratory standby that may be used is
Sauereisen Cement. This is a silicate based inorganic cement that sets very
hard. It adheres well to glass and metal. Though quite old, the company is
still very much in business, and today they make a broad line of very high
temperature adhesives. Many are rated for as high as 2500 F (1371 C).
Buying in small quantities may be a problem.

Having said all of this, I have several suggestions for finding these
materials.

High temperature silicone adhesive can be found in most auto parts stores
sold as Permatex Red (high temperature). A small tube is not very expensive
and you will surely find other uses in the shop. Their RED products are
rated for continuous service at 400 F (204 C) with intermittent service as
high as 700 F (371 C). This uses acetoxy cure chemistry, so acetic acid
will be released upon curing. Some of the RTV products use a two-part cure
and do not release acid fumes.

High temperature epoxy may be ordered from Omega (http://www.omega.com). I
suggest their Omega-Bond 200 epoxy which is a two-part epoxy that sets in
two hours at 400 F and is rated to 500 F. A two-ounce tube is available
from Omega for $12 US.

Omega also carries a line of the ceramic cements too. One type sets by
drying in air, the other type by chemically curing. Of the air-dry types,
Omega Bond 300, 400, and 500 are suitable; their maximum rated service
temperatures are respectively 982, 1426, and 1204 C (1800, 2600, and 2200
F). In the chemical curing types, Omega sells Omega Bond 600, 700, and CC
cements. These are rated respectively for 1426, 871, and 843 C (2600, 1600,
and 1550 F). For other details on mechanical properties and pricing, see
their website. Many of these are a little pricey. I suspect that they are
repackaged versions of the Sauereisen products. The "CC" product is about
the least expensive at $16 US.

For gluing on loose tube bases, I have used the really inexpensive
cyanoacrylate adhesives (super-glues) as well as silicone sealants. No
doubt some of the moisture curing urethane adhesives would work here too.

73, Barry WA4VZQ O

From: "Dr. Barry L. Ornitz" < >
To: Old Tube Radios < >
Subject: Addenda to: High Temperature Adhesives
Date: Fri, 30 Dec 2005 23:35:25 -0500

Friends,

In my recent post on adhesives for tube plate caps and other high
temperature applications, I noted that receiving tubes and low power
transmitting tubes did not reach nearly the temperature of many high-power
transmitting tubes. To get a "ballpark" figure, I looked up the maximum
surface temperature for a number of tubes. From the RCA Receiving Tube
Manual, I found that most tubes have a surface temperature of 200 C or less.
A few, like the 6JB6A used by Drake and the 6JS6C used by Japanese
manufacturers, can reach temperatures as high as 240 C and 225 C
respectively. Some other high power receiving tubes have a maximum surface
temperature of 220 C for the 6DQ5, and 6DQ6, 225 C for the 6KD6, and 250 C
for the 6LQ6.

For some other tubes we often encounter, I found 260 C for the 6080 and 200
C for the 6082 [R-390 owners note], 220 C for the 6146, 6146A and 6146W, 260
C for the 6146B, 200 and 225 C respectively for the base and plate seals of
the 4-400A, and 150 and 200 C respectively for the base and plate seals of
the 4-1000, 200 to 225 C for all seals of the 4-65, 200 C for the 572B, 145
C on the seals of the 833A and 250 C for the 6550 popular with audio folks.


So for even many of the high-power tubes which normally require forced air
cooling to maintain seal temperatures, their maximum allowable seal
temperatures are less than 250 C and sometimes much less. So it looks like
for the majority of applications an adhesive rated to 260 C or 500 F is
adequate.

As I noted, I have had good success with the Permatex high temperature
silicone which is the least expensive option and readily available almost
everywhere, and with the Omega-Bond 200 epoxy which is stronger but much
more expensive. I have used the Sauereisen cements industrially with good
success at temperatures around 1500 C, well above what is required for
securing plate caps.

73, Barry WA4VZQ

From:
Message-ID: < >
Date: Fri, 30 Dec 2005 23:59:26 EST
Subject: Re: Addenda to: High Temperature Adhesives
To: Old Tube Radios < >

Barry,

Any idea what the original cement used for plate and grid caps and tube bases
was?

Also, does it work better to let the Permatex cure before redoing the solder
connection or glue it, solder it and then let the adhesive cure?

In a message dated 12/30/2005 10:36:16 PM Central Standard Time,
t writes:
> As I noted, I have had good success with the Permatex high temperature
> silicone which is the least expensive option and readily available almost
> everywhere, and with the Omega-Bond 200 epoxy which is stronger but much
> more expensive. I have used the Sauereisen cements industrially with good
> success at temperatures around 1500 C, well above what is required for
> securing plate caps.

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
< > (Primary email)
< > (Backup email)

From: "Dr. Barry L. Ornitz" < >
To: Old Tube Radios < >
Subject: FW: Addenda to: High Temperature Adhesives
Date: Sat, 31 Dec 2005 01:09:36 -0500


Robert Downs, WA5CAB, asked:

> Any idea what the original cement used for plate and grid caps and tube
bases was?
> Also, does it work better to let the Permatex cure before redoing the
solder connection or glue it, solder it and
> then let the adhesive cure?

The original glue was a phenolic thermosetting resin with fillers. I
believe it was partially polymerized phenol-formaldehyde in composition. As
a thermoset, it can take pretty high temperatures. I believe that asbestos
brake pads are glued to the shoes with similar resins as well as the
asbestos in the pad itself. Until US-23 between Asheville, NC, and Johnson
City, TN, was replaced by I-26, it was common to smell the awful phenolic
odor from trucks burning their brakes on the steep hills.

Permatex is best cured before the soldering [but in an emergency, soldering
may sometimes be done first]. Remember that the one-part silicones will not
cure in sections deeper than about 1/4 inch. Two-part silicones, like GE
RTV-116, do not have this problem. One-part silicone systems release gases
(usually moisture or acetic acid) upon curing; the two-part systems do not.
Permatex is as one-part system so use just enough to hold the cap on; do not
scrape out the existing phenolic adhesive and fill the cap with the silicone
or curing may take many days. If you impede the diffusion of the gas out,
the silicone will not cure. This is why if you find an old tube of silicone
caulk where the cap has broken and the silicone is cured within the nozzle,
you will often find that digging the plug out will reveal uncured silicone
beneath.

73, Barry WA4VZQ




From: "Dr. Barry L. Ornitz" < >
To: "'Roy Morgan'" < >,
"'Old Tube Radios'" < >
Subject: Still more - RE: Tube Cap "Glue" [High Temperature Adhesives]
Date: Mon, 9 Jan 2006 04:39:47 -0500

Prompted by Roy Morgan's quoting of Lud Sibley's email on the composition of
tube basing cement, I did a little more research. Thanks, Roy!

The composition of the uncured cement was given as:

" The usual base cement was "No. 6," AKA "C6." The official recipe for this
was:

D3 Durite 7.5 lb.
S15 Shellac 19.5 lb.
R3 Rosin 3.25 lb.
M3 Marble flour 170.0 lb.
A4 Alcohol 9.0 l.
M19 Malachite green 10.0 g."

The Durite mention rang some bells for me. This is a phenol-formaldehyde
resin, now made by Borden Chemicals. In fact, they sell a tube basing
cement (or more properly " Lighting Basing Cement - Lamp Cement Resin"),
DURITER LC-5561B. They also sell just the resin as DURITER LD-5182.

Quoting from Borden's data sheet:

"Description: LC-5561B is a pulverized, novolac basing lamp cement.

Application(s):
LC-5561B is designed for basing (adhering glass bulb to base) incandescent
lamps, fluorescent lamps, etc. Typically, denatured alcohol is used to form
a paste with the LC-5561B, which is then dispensed manually or from
automatic or semiautomatic machines. A heat cure is subsequently used to
impart bond.

Benefits:
LC-5561B offers a heat resistant and dimensionally stable bond between glass
and brass, glass and aluminum, glass and molded plastics, etc."

Confused? Some background and definitions may be in order:

" Phenolic Resin:
Any of several thermosetting resins prepared by the condensation of phenol
with aldehydes (formaldehyde, acetaldehyde, furfural, etc.). Phenolic resins
were first made in 1872 when Adolph Baeyer reacted phenol with acetaldehyde.
Bakelite phenolic resins were developed by Leo Baekeland beginning in 1907.
Examples of phenolic resins are Bakelite, novolac and Catalin. Phenolic
resins are used for molded parts, as adhesives and as varnishes.

Synonyms:
phenol resin; phenoplast; Bakelite [Union Carbide]; Fiberloid [Monsanto];
novolac; Catalin; Marblette; Agatine; Durite; Durez; Prystal; Fiberlon;
Opalon.

Phenol-Formaldehyde Resin:
A thermosetting amino resin that is made by reacting phenol with
formaldehyde. Discovered in 1907 by Leo Baekeland and sold as Bakelite in
1909, phenol formaldehyde resin was the first true synthetic plastics.
Phenolic resins can be made with either excess formaldehyde (resol) or with
an excess of phenol (novolac). Resols are soluble in alcohol while novolacs
are solid at room temperature. Both require cross linking to form a hard
plastic that is brittle but has good resistance to water and biodegradation.
In the early 20th century, phenol formaldehyde resins were used for dark
color molded plastic products sometimes filled with cellulose, wood flour or
mineral powders. Resol phenolics are currently used for plywood, textile
sizing, leather processing, paper strengthening, foams and chemical
resistant coatings. Novolacs are used for fibers, adhesives, molded parts,
circuit boards, and mechanical fittings."

By the way, Durite LC-5561B is sold in 200-pound drums if anyone is
interested in purchasing the material. DURITER LD-5182 is sold in 250-pound
drums. I doubt if either is very expensive, but the hazardous waste permits
for getting rid of the excess might be a problem.

But what about the other materials in the recipe and their functions?

The marble flour is just very finely ground calcium carbonate and is used as
an inorganic filler. The alcohol is there to dissolve the novolac resin and
make a paste. Most likely the alcohol is methyl alcohol which has better
solvent properties in this application than ethanol or isopropanol. The
alcohol also dissolves the shellac and rosin. These serve only to make the
paste more adhesive (known as tackifiers in the industry). The rosin may be
from either pine tree roots (wood rosin) or sap (gum rosin), generally
obtained as a byproduct from the Kraft process for papermaking. At the
curing temperature, most of the rosin and shellac bakes out or chars. They
have little effect on the cured resin. The interesting component is
malachite green.

The malachite green is NOT malachite, a green, copper containing mineral,
Copper Carbonate Hydroxide, or Cu2(CO3)(OH)2. Malachite green is an aniline
dye, so named because its color mimics the mineral. It is also known as
Basic Green #4. It makes the raw cement green, but after baking, the final
color is brown. Chemically, malachite green (hydrochloride) is
C24H25N2O2.HCl. People who keep aquariums may be familiar with it as an
antifungal for fish.

Based on the composition of this basing cement, I do not think there was any
special effort to make it match the thermal expansion of glass. Note that
since Durite LC-5561B is used to bond between glass and aluminum, brass or
plastics, and these have widely varying thermal coefficients of expansion.

Lud Sibley also wrote:

" There's been some talk in restorer circles as to the cured cement being
soluble in toluene, acetone, etc. I haven't had any luck. In the old days,
if the RCA warehouse discovered loose bases, they just fixed them with
shellac."

The cured cement might be attacked by strong acids, dissolving the calcium
carbonate, but the cured phenol-formaldehyde resin is a fully cross-linked
thermoset polymer, essentially soluble in nothing! In fact, if you have
grandchildren who ask what a molecule looks like, show them a piece of cured
phenol-formaldehyde resin. Every atom in the piece is connected
(cross-linked) to another atom. The entire block is just one big molecule.

Toward the end of Roy's note, there is mention of Grainger's Furnace and
Retort Cement: This is an inorganic cement somewhat similar to the very
high temperature cements I mentioned, but not nearly as strong. While the
sodium silicate (which is actually only one component of the cement) will
bond well to glass, it will produce a bond that will loosen when wet, and
may produce conductive salts when moist or when in contact with metals. For
a plate cap, this should not be a problem, but I would avoid it around tube
bases. [Mixing sodium silicate solution with zinc oxide and finely ground
chalk will produce a "rock-hard" material that will function as a glue
(known in the trade as "professional pyrotechnic adhesive", it was commonly
used to glue on the end caps for M80's). But the proportions must be
correct as excess sodium silicate will cause problems.]

If anyone needs datasheets on the two Borden DuriteR products I mentioned,
please write. I have them as Adobe PDF documents.

73, Barry WA4VZQ


From: "Dr. Barry L. Ornitz" < >
To: "'Dr. Barry L. Ornitz'" < >,
"'Roy Morgan'" < >,
"'Old Tube Radios'" < >
Subject: RE: *** SPAM *** Still more - RE: Tube Cap "Glue" [High Temperature Adhesives]
Date: Mon, 9 Jan 2006 04:45:21 -0500

Note that on my previous post, theporch.com must not accept the "copyright"
symbol as a valid character. Where you see DURITER in my previous post, it
is actually DURITE (registered copyright symbol). Sorry if there was any
confusion.

73, Barry WA4VZQ


Regards,
Last edited by NECRAT on Tue Sep 15, 2020 2:16 pm, edited 1 time in total.
Reason: Removed visible email addresses
James K. (Jim) Thorusen
KB6GM
Central Coast Electronics
www.centcoast.com
NW Oregon Consulting Bdcst Eng.
NECRAT
Site Admin
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Re: 813 Tube Repair

Post by NECRAT »

jthorusen wrote: Tue Sep 15, 2020 2:40 am Here is the entire E-mail thread that went by many years ago on this subject. Some highlights are for:

From: "russ dworakowski" < >
To: Old Tube Radios < >
Subject: Re: Tube base cement - failure mode
Date: Fri, 13 Sep 2002 01:07:49 -0400
Mime-Version: 1.0
Content-Type: text/plain; format=flowed
Message-ID: < >
When copying an email like this to a public forum, please take care to mask email addresses, so they aren't skimmed for scammers/spammers.
I have edited them out.
Mike Fitzpatrick
Broadcast Engineer/Tower Photographer
Boston area.
https://www.necrat.us, https://www.scan-ne.net/

"If you don’t think you’re good, nobody else will" - Tom Laun (RIP)."
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Re: 813 Tube Repair

Post by jthorusen »

I will do this in the future. I thought the whole thing might be necessary for proper attribution or if someone wanted to contact an original poster for more info. However, I can always supply the address in a PM if someone wants more detail.

Thank You,
James K. (Jim) Thorusen
KB6GM
Central Coast Electronics
www.centcoast.com
NW Oregon Consulting Bdcst Eng.
NECRAT
Site Admin
Posts: 3220
Joined: Sat Nov 17, 2007 9:13 pm
Location: Taunton, MA
Contact:

Re: 813 Tube Repair

Post by NECRAT »

jthorusen wrote: Tue Sep 15, 2020 6:59 pm I will do this in the future. I thought the whole thing might be necessary for proper attribution or if someone wanted to contact an original poster for more info. However, I can always supply the address in a PM if someone wants more detail.

Thank You,
That's what I figured, if someone wants it, they can PM you. Thank You!
Mike Fitzpatrick
Broadcast Engineer/Tower Photographer
Boston area.
https://www.necrat.us, https://www.scan-ne.net/

"If you don’t think you’re good, nobody else will" - Tom Laun (RIP)."
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