[AMRadio] UPDATE: Testing Transmitting Tubes


flderoos at mmmpcc.org flderoos at mmmpcc.org
Tue Oct 19 19:10:09 EDT 2004


Mark,

I haven't been part of this discussion so far, but would be interested in seeing
the schematic for your tube curve tracer.  I've thought about building a tester for
transmitting tubes, but haven't gotten past the thinking stage.  I guess one way
would be to build an oscillator circuit and test them as power oscillators similar
to the induction heating circuits.

Thanks,

Fred
WA0GMH

Mark Foltarz wrote:

> Hey Don,
>
>   Sounds good!
>
>   How would you like to build a curve tracer also?
>
>   I built a tube curve tracer for audio tubes about 10 years ago.  I found the
> schematic the other day. Come to think of it I also have the the actual unit.
>
>   The idea is to use unfiltered half wave as the plate supply - simple sweep
> eh?
>
>   Build a step generator to put successive voltges on the grid - one higher
> than the previous  with each plate voltage cycle.
>
>   Measure the plate voltage against the current on the x & y traces of a scope.
>
>   And you get the family of curves for that tube.
>
>   Let me know if you want a copy of that old schematic.
>
>   de KA4JVY
>
>   Mark
>
>
> --- Merz Donald S <merz.ds at mellon.com> wrote:
>
> > Just thought I'd throw out an update on this. I am building an emission
> > tester for older, mostly 800-series transmitting triodes. It will be able to
> > measure emission current at zero bias or adjustable bias (using an external
> > bias supply) at any plate voltage up to about 2500V. The HV is full-wave,
> > lightly-filtered DC. Filament voltage is adjustable 0-10VAC. I have an old
> > metered, rackmount regulated supply that uses dual 6L6's for regulation. It
> > will do 100V--so he becomes the bias supply.
> >
> > I gutted an old Beckman, tube-type frequency counter to use the cabinet and
> > chassis. I just happened to have this unit laying around here. It has a
> > unique cabinet design with sides that come off and modular chassis
> > construction--even though, underneath the covers, it's a conventional 8.75
> > inch high, 19" rackmount unit. This design allowed me to remove sections of
> > the chassis to accommodate the 2 big Variacs and the big HV iron. The top of
> > the cabinet pops off with just 2 Dzus fasteners. I am going to put holes in
> > the top with the tube sockets underneath, mounted on an inverted chassis
> > bolted to the top cover. This way the whole unit won't have any protrusions
> > or non-internal wiring and none of the tube socket connections will be
> > exposed or accidentally accessible.
> >
> > I drilled and painted the panel Sunday. I then immediately discovered that
> > the 0-300ma meter I was using did not have enough range at upwards of 2500V.
> > I needed at least 6-800ma. So I replaced that meter with a 0-1000ma Simpson.
> > But of course, the hole size is different. So now I have to cut a larger
> > meter hole on my already-painted aluminum front panel. I took comfort from
> > the fact that the black wrinkle didn't turn out that great anyway...
> >
> > Most of the parts for this thing came from a supply I bought at a hamfest in
> > 2003. For $40, it had a 7.5 amp 120V Variac, 2700V transformer (amps rating
> > unknown but probably in the 500ma range), 4 K2AN silicon HV rectifiers and a
> > bodacious capacitor bank of paralleled 800MFD, 450VDC caps. The meters I am
> > using are from the junkbox (note to self: Don't buy any more meters at
> > hamfests...), as are the sockets and miscellany. But anyone seeking to build
> > one of these with new parts would have a big bill on their hands. Check the
> > prices on new 7.5 amp Variacs these days...
> >
> > I expect to be able to test to following tubes in this unit: 203, 211, 805,
> > 808, 810, 838, 852, 25T(G), 35T(G), 100TH, 250TH and RK-65. The test is far
> > from definitive. But it will tell me whether the spares I am saving are worth
> > saving.
> >
> > The top cover is big enough that I will still have some space for tetrode and
> > pentode sockets. Screen and suppressor supplies would have to be external.
> > But that is phase II--or something I may never do at all.
> >
> > 73, Don Merz, N3RHT
> >
> >
> > -----Original Message-----
> > From: owner-glowbugs at piobaire.mines.uidaho.edu
> > [mailto:owner-glowbugs at piobaire.mines.uidaho.edu]On Behalf Of Merz
> > Donald S
> > Sent: Tuesday, September 21, 2004 3:27 PM
> > To: 'Amradio (E-mail); 'Glowbugs (E-mail)
> > Subject: GB> UPDATE: Testing Transmitting Tubes
> >
> >
> > Well, here's where I am with this...
> >
> > -- The guy who built the tester that AES is using says that he has some
> > information on that unit that he will pass along.
> >
> > -- Another guy says that he has built an adapter for the Tektronix 577 curve
> > tracer for transmitting tubes. He says that he will write this up for
> > Electric Radio.
> >
> > -- Two guys said that they built custom testers for the 4CX250 tube. One of
> > them was expanded to test other tubes and was demo'ed at Dayton. The other
> > was used in the guy's job. No details seem to be available for either of
> > these.
> >
> > -- I checked the AWA index and found only one reference to testing
> > transmitting tubes. It's a 50 word mention on page 21 of Volume 22, number 1.
> > There is one diagram. The test the guy is proposing is a minimal emissions
> > test using a known good tube as a reference. He does this for triodes only
> > using AC both on the filament and on the plate & grid (which are connected
> > together). It has the virtue of being simple. But it hasn't many other
> > virtues.
> >
> > -- Finally, there is the e-mail below from the AWA's Ed Gable. This seems to
> > be closest to the lines along which I am thinking--a scaled down emission
> > tester.
> >
> > The GE Ham News Hartley oscillator tester is more complicated than I want to
> > get into. And the Ham News static tester is very similar to the AWA tester
> > described below.
> >
> > So this is where I am headed, though still open to better ideas. Keeping it
> > simple, so triodes only at this point.
> >
> > 73, Don Merz, N3RHT
> >
> >
> > -----Original Message-----
> > From: Edward Gable [mailto:EGABLE at rochester.rr.com]
> > Sent: Monday, September 20, 2004 2:11 PM
> > To: Merz Donald S
> > Subject: Re: Testing Transmitting Tubes
> >
> >
> > Hi Don:  We built a tube tester for Big TX tubes at the AWA Museum.
> >
> > 1.  Use big filament Xfmr and variac to accomodate any FIL voltage.  Use FIL
> > voltmeter.
> > 2.  Use variace on HV supply for 0 to about 1500 volts.  Need about 300 Ma,
> > but not too much filtering.
> > 3.  Put voltmeter and ammeter in HV supply.
> > 4.  Parallel wire a bunch of convenient tube sockets and allow for clip
> > leads for socket-less tubes like 833.
> > 5.  To test, get tube data for tube.  Look at chart and see what the tube
> > current should be for a
> > tube with zero bias.  For example, a type 810 might draw 200 Ma @ 1500 volts
> > with zero bias.
> > 6.  Connect the grid to the filament (zero bias condition)
> > 7.  Turn the FIL on and set proper voltage for the tube under test.
> > 8.  Turn up the HV variac and watch the current & voltmeters.  See if the
> > current vs voltage is close
> > to the spec.  It varies a lot from tube to tube, but low emission,
> > non-useable tubes really show up
> > this way.
> >
> > SAFETY FIRST !!!
> >
> > 73,
> >
> > Ed Gable  k2mp
> > Curator, AWA Museum
> >
> > ----- Original Message -----
> > From: "Merz Donald S" <merz.ds at mellon.com>
> > To: "'Amradio (E-mail)" <amradio at mailman.qth.net>; "'Baswaplist' (E-mail)"
> > <baswaplist at foothill.net>; "'Glowbugs (E-mail)"
> > <glowbugs at piobaire.mines.uidaho.edu>
> > Sent: Monday, September 20, 2004 10:19 AM
> > Subject: Testing Transmitting Tubes
> >
> >
> > > Has anyone built a transmitting tube tester? Or seen any plans on the web?
> > The only thing I have seen on this subject is the issue of GE Ham News that
> > covers the subject (Vol 6, #3, May/June, 1951). I have some power supplies I
> > can use to run the static test. But I need to build something to hold the
> > tube sockets, filament transformers and plate current meter. I hate to
> > reinvent the wheel and would be happy to follow a pre-existing design if I
> > could find one...
> > >
> > > Any ideas?
> > >
> > > 73, Don Merz, N3RHT
> > >
> > > The information contained in this e-mail may be confidential and is
> > intended solely for the use of the named addressee.
> > > Access, copying or re-use of the e-mail or any information contained
> > therein by any other person is not authorized.
> > > If you are not the intended recipient please notify us immediately by
> > returning the e-mail to the originator.(A)
> > >
> >
> > The information contained in this e-mail may be confidential and is intended
> > solely for the use of the named addressee.
> > Access, copying or re-use of the e-mail or any information contained therein
> > by any other person is not authorized.
> > If you are not the intended recipient please notify us immediately by
> > returning the e-mail to the originator.(A)
> >
> > The information contained in this e-mail may be confidential and is intended
> > solely for the use of the named addressee.
> > Access, copying or re-use of the e-mail or any information contained therein
> > by any other person is not authorized.
> > If you are not the intended recipient please notify us immediately by
> > returning the e-mail to the originator.(A)
> > ______________________________________________________________
> > AMRadio mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/amradio
> > Help: http://mailman.qth.net/mmfaq.html
> > Post: mailto:AMRadio at mailman.qth.net
> >
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
> ______________________________________________________________
> AMRadio mailing list
> Home: http://mailman.qth.net/mailman/listinfo/amradio
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio at mailman.qth.net




More information about the AMRadio mailing list

This page last updated 23 Oct 2017.