[Amps] 3-500z - intermittent filament

[Robert B. Bonner]

Guys,

I have done this countless times for people without wrecking the tube.

Heat the pins with a big soldering iron and gently remove from the tube,
clean bare pin and tin.  Heat again and clean the inside out thoroughly.
Mount the pins in a fixture that can handle torch heat and center it. I used
an old tube socket clamped in a vise.  I already mentioned a fixture could
be machined that you would heat evenly.  I Used a regular BUNZ-O-MAtic
Torch.

Utilize either regular solder or Silver solder, if you use silver use STAY
BRITE, pure silver solder has a HIGHER MELTING POINT THAN TIN / LEAD.  PLUS
you will need to add paste rosin flux instead of the usual plumbing acid
core the goof at the plumbing shop would try and sell you.

Heat the two pins simultaneously with the torch, fill the pins about 5/8th
the way full with molten solder and add rosin flux...  Toast the pins up
good.

Then carefully and without dawdling while still applying heat to the pins
(You really want that socket clamped safely) push the tube down into the
pins, using the other pins in the socket as a locator.

I used a hair drier INSTANTLY to start cooling the pins...

Remove tube, polish the pins on the outside, take cold shower...  Not a
problem, you are now a REAL STUD, a Man's Man, Radio GOD, really cool guy.

However if you drop the tube, blow a seal, burn your hand, start the garage
on fire...  (or try and do this with the old socket bolted into your SB-220
my favorite) You'd be three feet below Whale POOP.

BOB DD 

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of k7rdx
Sent: Friday, February 09, 2007 7:44 AM
To: n4zr at comcast.net; amps at contesting.com
Subject: Re: [Amps] 3-500z - intermittent filament

There is a heat transfer/absorbant compound used in the auto collision
industry that may work very well for re-soldering filament pins.We used a
mud like substance to absorb heat when welding in sensitive areas and it
should be obtainable from most auto body suppliers. When work has been
completed you can remove with water rinse...Jim
----- Original Message ----- 
From: <n4zr at comcast.net>
To: <amps at contesting.com>
Sent: Thursday, February 08, 2007 8:05 AM
Subject: Re: [Amps] 3-500z - intermittent filament


> I'm sure John is correct about both the risks of resoldering and the ideal
solution, but what to do if you have tubes that have already failed from
this cause?
>
> Using some of Rich Measures' silver solder and packing the area around the
glass seal with wet paper towels, I have successfully repaired several
tubes.  Last time around, operating on the theory that the spring clips on
the filament pins might have lost their temper, I swapped them for those on
grid pins from the same socket.  I also made a point to polish the inside of
the socket contacts and the filament pins in the hope of reducing the
resistive heating at that point.  These fixes have so far been effective in
intense CW and SSB contest use for several years.
>
> 73, Pete N4ZR
>
> -------------- Original message -------------- 
> From: "John E. Cleeve" <g3jvc at jcleeve.idps.co.uk>
>
> > I would advise caution in resoldering the sleeved pins of the 3-500 et
al
> > tubes, for the Eimac spec. and the late Bill Orr, warned that the
melting
> > point of the solder used, could be very close to the temperature which
> > would destroy the glass to metal seal of the filament pins..........more
> > effective electrical contact, between the tube filament pin sleeves and
> > sockets, with more effective directed forced air cooling of the tube
base
> > sockets are the routes to follow.....but this has all be said
> > before.....regards, John G3JVC.
> >
> >
> > ----- Original Message ----- 
> > From: "Steve Thompson"
> > To:
> > Sent: Thursday, February 08, 2007 12:15 PM
> > Subject: Re: [Amps] 3-500z - intermittent filament
> >
> >
> > >
> > >
> > > terry at g4amt.com wrote:
> > >
> > >> The pins are riveted over on the tube side of the `former` so they
cannot
> > >> (?) be removed; they are of `split` construction. The only way I
could
> > >> re-solder them was to use a solder sucker to extract the old solder -
put
> > >> a
> > >> couple of drips of flux in the hole and re-solder with silver solder;
> > >> heating the pin with a mini-blowlamp ...
> > >
> > > A question as to what should be used here? There's 'silver solder' as
> > > used with a torch for brazing. There's also standard pcb solders with
> > > added silver content to give them a lower melting point than straight
> > > tin/lead.
> > >
> > > Steve
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