[R-390] Tube cutting 101

[AI2Q Alex]

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