Use for open-filament 8877?
David Feldman
An amplifier recently purchased arrived with an open filament 8877. Whether
caused by mishap in transit or other means will probably be a mystery, but
I'm now wondering what use (if any) can be made of such a tube? Any ideas?
73 Dave WB0GAZ d...@netcom.com
a...@pacifier.com
Have never seen it advertised, but these tubes could probably be recycled
if there was the $$ motivation. Call up Svetlana. They might have much
higher motivation for recycling. Doesn't seem like there is much interest
left in US in tube manufacture now that Russians and Chinese are getting
way up on the learning curve.
Robert Bissett
David Feldman wrote:
>
> An amplifier recently purchased arrived with an open filament 8877. Whether
> caused by mishap in transit or other means will probably be a mystery, but
> I'm now wondering what use (if any) can be made of such a tube? Any ideas?
>
> 73 Dave WB0GAZ d...@netcom.com
If it is a new US-made tube call or write the tube manufacturer.
They are always interested in these kind of things and may give
you credit towards a new one ( at least you'll get some sympathy).
Bob ND2L
--
*********
Bob Bissett rbis...@monmouth.com
*********
David Feldman
In article <dgfDxy...@netcom.com> d...@netcom.com (David Feldman) writes:
>An amplifier recently purchased arrived with an open filament 8877. Whether
>caused by mishap in transit or other means will probably be a mystery, but
>I'm now wondering what use (if any) can be made of such a tube? Any ideas?
The original shipper of the amplifier is assisting me with recovering from
the mishap, but I thought I'd share the following info supplied by Cliff,
K7RR, cbut...@slonet.org:
>Unfortunately, David, that happens rather often. Many of us have survived
>for years with 8877 tubes that have been discarded when the filament opens
>up. The cause usually is a bad spot weld on the filament support.....but
>then who cares about the theory when the tube is bad anyway. Mechanical
>shock will usually reconnect the filament but remains connected only as
>long as the voltage continues to be applied. So for the ham, beat on the
>fool thing until the filament connects by showing current and then operate
>until you must disconnect. Then repeat the next night! Cliff K7RR
(and...)
>I was delighted to relate how "us poor folk" get on two
>meters with a whapping signal. Be careful how you beat on the tube---high
>voltage of course. Cliff K7RR
Thanks, Cliff, for interesting info!
73 Dave WB0GAZ d...@netcom.com
William L. Fuqua III
>Date: Thu, 19 Sep 1996 05:23:42 GMT
>From: d...@netcom.com (David Feldman)
>Subject: Use for open-filament 8877?
>
>An amplifier recently purchased arrived with an open filament 8877. Whether
>caused by mishap in transit or other means will probably be a mystery, but
>I'm now wondering what use (if any) can be made of such a tube? Any ideas?
>
>73 Dave WB0GAZ d...@netcom.com
>
EIMAC rebuilds some tubes. I don't have the list of tubes that they
rebuild but at least the larger tubes such as the 3CX15,000A7 the
rebuilt one is about half the price. The part number is the
same except that it has an "R" after the normal part number.
I just checked a couple of weeks ago about this.
73 Bill wa4lav
William L. Fuqua III P.E. E-mail WLFU...@POP.UKY.EDU Phone (606) 257-4155
Department of Physics and Astronomy CP-177 Chem. Phys. Bldg.
University of Kentucky , Lexington, Ky 40506-0055
J. Fred Riley
wlfu...@service1.UKy.EDU (William L. Fuqua III) wrote:
> EIMAC rebuilds some tubes.
So does Econco and Freeland Products. But the 8877 uses an
oxide-coated cathode, not a filament. I am unaware of any company who
rebuilds a tube with a heater structure that small. It would probably
cost as much to rebuild a tube that small as it would cost to replace
it outright.
I have never seen an open heater in one of these tubes that had an
intact seal; they've usually gone to air and been destroyed
internally. You also rarely see an open filament unless a tube has
gone to air because of a cracked seal. In either case they're
non-rebuildable since the structures inside are destroyed in the
"fire."
Just as an aside, rebuilding involves recarburizing a filament
structure. Methane gas is introduced and the temperature of the
filament is run very high. The surface of the filament is converted
by this process to di-tungsten carbide which is both very fragile and
a terrific electron emitter.
Fred
JFR...@AIRMAIL.NET
FREDW...@AOL.COM
7066...@COMPUSERVE.COM
W8JI Tom
In article <522eae$8...@library.airnews.net>, jfr...@iadfw.net (J. Fred
Riley) writes:
>
>So does Econco and Freeland Products. But the 8877 uses an
>oxide-coated cathode, not a filament. I am unaware of any company who
>rebuilds a tube with a heater structure that small. It would probably
>cost as much to rebuild a tube that small as it would cost to replace
>it outright.
Fred is exactly correct on everything he said. It's pretty tough to
rebuild an oxide cathode tube, especially a small one. They might as well
throw it out and start over.
I've only very rarely found an open filament in an 8877. The usual failure
is a grid to cathode short caused by structural probelms or operation with
sustained high grid currents. The second most common failure is loss of
emission due to stripping of the cathode (high current demand with low
temperature) or many, many hours of heater time.
While open filaments happen, they are the rarest of problems I've seen. In
the products I'm associated with.
The photons beaming down from space / parasitic failure stuff is another
bunch of hoo-doo.
73 Tom