[R-390] Tube cutting 101

[Ray, W2EC]

I seem to recall a method where you use a small wire that you hook up to
a 12 volt car battery until its glowing good and hot, then quickly wrap
it around the tube where you want the break to occur and dip it quickly
into water. The hot wire heats the tube at the break point and the rapid
cooling snaps it cleanly off. Anybody remember/try this technique?

73, Ray  W2EC


AI2Q Alex wrote:
> 
> Hi Barry:
> 
> After trying to cut open some sacrificial tubes using a few scribe-and-snap
> techniques, I arrived at a better way using a Dremel tool and thin cutting
> wheel.
> 
> I place the Dremel motor in a drillpress vise, and set the vise on my
> workbench so that the direction of rotation is away from me. Donning
> protective glasses, I then crank the motor up to top speed. Holding the 7-
> or 9-pin tube using gloves, I carefully rotate it against the cutting blade.
> 
> The point of contact actually glows red, which leads me to believe that the
> friction at that point may actually be melting the glass as well as
> "cutting" through it. In any case, the result is the same: I get a nice
> clean break. You have to fiddle a bit to get the right pressure and speed at
> which you rotate the tube against the wheel, but after a short learning
> curve, you can open these jobbies up and enjoy a low scrap rate. Naturally,
> you don't do this with rare tubes such as 7360s. You do it with defunct
> 6BA6s and 6AQ5s and the like.
> 
> Once opened, I remove the innards, and solder-in my solid-state devices.
> Closing the tube (after inserting a mandatory slip of paper with my
> callsign, date, tech info, etc.) is done with some Crazy Glue.
> 
> Vy 73, AI2Q, Alex in Kennebunk, Maine    .-.-.
> 
> -----Original Message-----
> From: Barry Hauser [mailto:barry@hausernet.com]
> Sent: Wednesday, January 16, 2002 1:02 PM
> To: ai2q@adelphia.net; 'Steve Goode'; r-390@mailman.qth.net; 'Roger L
> Ruszkowski'
> Subject: Re: [R-390] 6DC6 Replacement
> 
> Alex wrote:
> .> I confess! I've poked JFETs into both 26C6 mixers on my R-392, and those
> > 24-V stages work really well. I used a Dremel tool cutter to scribe the
> > glass of 7-pin miniature tubes, cracking them open and removing the
> innards.
> > I then soldered the JFETs with drain source and gate connected to the old
> > plate, cathode, and grid leads, respectively. After inserting a label with
> > my callsign on it, I then glued the glass envelopes closed. I popped 'em
> > into the R-392, where these solid-state jobbies perform flawlessly. I can
> > elaborate about the glass cutting procedure if you're interested.
> .
> Am I to understand that you failed to replace the vacuum with fresh, uh,
> nothing? ;-)
> 
> For effect, you're allowed to add a mini orange LED for glow, but it should
> be driven by a EEPROM so it blinks the following message in code:  "Warning
> to hollowstaters:  Glass envelope contains solid state components which may
> be offensive to your sensibilities.  This message in compliance with Truthi
> in Thermionic Emissions Act of 2002."  If you use more than one of these,
> they must be synched.
> 
> Seriously though -- I'm interested in your tube cutting technique.  Handy to
> make up 7 and 9 pin plugs out of bad tubes.
> 
> Barry
> 
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