[Lyle Harbour]

Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish
the cages and clean the pins.

All was going well until one 300b came out but the base stayed in the
amp, The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle

[Patrick Turner]

Lyle Harbour wrote:

Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish
the cages and clean the pins.

All was going well until one 300b came out but the base stayed in the
amp, The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle

You could try the Sellys 401 silicone sealant which
can withstand 200C OK.
The socket is unlikely to get that hot.
Otherwise some hi temp epoxy that will stick to glass is required
and I have never had your problem eith a hot output tube
so I cannot advise further.
A google search should bring something up
which will not break down with heat, but remain glued
but not crack the glass or base.

Patrick Turner.

[David R Brooks]

Patrick Turner wrote:

Lyle Harbour wrote:
Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish
the cages and clean the pins.

All was going well until one 300b came out but the base stayed in the
amp, The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle

You could try the Sellys 401 silicone sealant which
can withstand 200C OK.
The socket is unlikely to get that hot.
Otherwise some hi temp epoxy that will stick to glass is required
and I have never had your problem eith a hot output tube
so I cannot advise further.
A google search should bring something up
which will not break down with heat, but remain glued
but not crack the glass or base.

What was originally used? I expect it's no longer available, though.

[Patrick Turner]

David R Brooks wrote:

Patrick Turner wrote:

Lyle Harbour wrote:
Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish
the cages and clean the pins.

All was going well until one 300b came out but the base stayed in the
amp, The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle

You could try the Sellys 401 silicone sealant which
can withstand 200C OK.
The socket is unlikely to get that hot.
Otherwise some hi temp epoxy that will stick to glass is required
and I have never had your problem eith a hot output tube
so I cannot advise further.
A google search should bring something up
which will not break down with heat, but remain glued
but not crack the glass or base.

What was originally used? I expect it's no longer available, though.

It was a sort of brownish foamy sort of glue, and used on many tubes for
a
long time until they did away with bases and placed the pins in the
glass.
It failed eventually in large numbers of tubes, but if ppl were careful,
they
don't pull a tube out by the glass, they grip it around the base and
pull, perhaps
levering up with a screw driver to avoid the glass coming loose from its
base.
Sockets were once always bolted into chassis metalwork, but this never
happens now,
and they recess the tube down to reduce the amp height, because size
costs money.
They don't care that the amp runs hotter.

There is always no shortage of arsole designers wanting to cheapen up
the
manufacturing process to make it 20dB harder for a tech to fix the darn
thing,
or 20dB more likely that simple easy practice used in the past
is no longer possible, and that the alternative is likely to damage
something.

Patrick Turner.

[Phil Allison]

"Lyle Harbour"

Yesterday I decided to give my amps a clean , Remove the dust ,polish the
cages and clean the pins.


** Fatal mistake .....


All was going well until one 300b came out but the base stayed in the amp,
The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?


** You re-attach the base by re-inserting the leads and properly
re-soldering them inside the pins.

The glass ought to still be a neat fit in the base and it is easy to fill
any tiny gaps/ cracks with good old Super-Glue.

Stands up to heat surprisingly well.

Adheres to glass and the old ( resin ?) glue.




......... Phil

[Patrick Turner]

"François Yves Le Gal" wrote:

On Sun, 06 May 2007 07:33:49 +1000, Lyle Harbour
wrote:

What would be a suitable adhesive/cement to use to reattach the base?

It all depends on the actual 300B.

If it's a vintage tube, you can usually reuse the original cement by
softening it with isopropyl alcohol, remount the base then cure the assy' by
gently baking the tube in an oven set between 150 and 175° C for 30 to 45
minutes.

If it's a modern tube, remove the cement with a suitable solvent then use
either specialized glue (best), high temperature two-part epoxy (good) or
cyanoacrylate glue (acceptable).

Cf. http://www.jacmusic.com/accesories/T...ube-glue-.html for more
info.

BTW, you should never pull a large tube by it's glass.

I have assumed he would do what Phil nominated, ie,
clean up the wires and clean out the base pins, and slide the
wires back down the hollow pins before resolderning.

During this process there is a large chance Lyle doesn't get the right
wires into the right
pins.
OK, he solders up the pins neatly without excessive solder, glues the
tube into the base
and re-inserts the tube into the circuit.

At turn on, if everything goes as horribly wrong as could be expected,
the cathode is a direct connection between OPT and anode is to the grid
connection,
and grid is to the other side of the cathode supply.

Then he gazes into the amp wondering why there is no signal.

While he checks the speaker leads, then interconect leads,
preamp, CD player,
there is a loud bang as the cathode bypass cap explodes
after of course the cathode resistor has gone open.
The power trannies are scorching hot and B+ remains low; oops,
the PT has shorted turns and needs replacememnt.
Sometimes the cathode bypass cap doesn't explode and just sullenly
shorts,
and the mains trannies suffer an open HT winding, so no B+ at all.
Sometimes the OPT primary goes open.

He hasn't reacted to the smell of serious trouble......

And nobody had fitted any active protection...

Now we could all smile at this devestatingly depressing scenario,
but I have two 10 watt SUN amps here with a pair of 2A3 in each and the
owner stuffed not one, but both
because the 4 pin tube socket would accept the 2A3 in about any
position,
and perhaps the owner never noticed why it must have been a bit harder
to poke the tubes in
one way rather than another, and just shoved 'em in any old way.

We couldn't buy the right kind of spares for these lovely old amps, so
we got a set from Hammond,
who make a suitable
HT tranny, and a second tranny for the two 2A3 cathodes.
I am just about to do this re-build work and don't know if the original
tranny covers
can be retained for appearances' sake.

So **** can happen alright.

Some ppl are very zealous about cleaning their amps and do it regularly
(after they have done the 1960 Jag in the driveway) and smear all sorts
of **** down the tube socket holes.
Usually the grid connection is the first to become disconnected
due a combination of corrosion and loosened grip of the socket pin
grippers.

This can cause complete bias failure for the tube, and it self distructs
right there in front of them if they ain't in the kitchen fetching a cup
of tea
while the amps warm up. Without active protection which is rarely ever
fitted to any tube amps,
this can be a very expensive disaster.

Patrick Turner,

[maxhifi]

Buy a new tube, unless it's a WE or something super expensive.

"Lyle Harbour" wrote in message
...
Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish the
cages and clean the pins.

All was going well until one 300b came out but the base stayed in the amp,
The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle

[Lyle Harbour]

Thanks , Patrick, David, François, and Phil for your replys

Good Info http://www.jacmusic.com/accesories/T...ube-glue-.html

It is a modern tube AVVT 300b-SL , with brown glue, That seems
impervious to solvents.

This is the first time the tubes have been removed since they went in 3
years ago.

After the base separation , I have changed the way I remove these tubes
too. Grabbing the top of the tube an making a gentle spiraling motion
The tube does the motion not me, would look funny though .

Have decided to go with the silicone adhesive , 230c tolerant to heat
and the two wires with the bigger blobs of solder went back into the two
larger pins, measures 1.2ohms between the two large pins , Both tubes

Thanks for the tips

Lyle









Lyle Harbour wrote:
Hi, Tube Guys

Some expertise is sought

Yesterday I decided to give my amps a clean , Remove the dust ,polish
the cages and clean the pins.

All was going well until one 300b came out but the base stayed in the
amp, The socket is on a board below the top of the metal case.

The tube is ok the wires detached from where they were soldered
I have been able to remove the base

What would be a suitable adhesive/cement to use to reattach the base?

Thanks
Lyle