|[AMRadio] UPDATE: Testing Transmitting Tubes|
Merz Donald S
merz.ds at mellon.com
Tue Sep 21 15:26:39 EDT 2004
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
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
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
SAFETY FIRST !!!
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
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