Subject: glowbugs V1 #202
glowbugs Tuesday, December 9 1997 Volume 01 : Number 202
Date: Wed, 3 Dec 1997 12:18:04 -0600 (CST)
From: Dave <nyet@ix.netcom.com>
Subject: Tube tester advice
Hi all,
I need to acquire a tube tester to keep up with all my boatanchors. I
also have a bunch of tubes that should be sorted, tested/evaluated,
and boxed in nice new Antique Electronic Supply bulk boxes.
What kind should I get? I don't want to spend a fortune (like for some
of the old Navy rigs I hear about that are $200 and up), but I need
something reasonably effective. I once knew the different types of
testers, but that was 20 years ago and I have forgotten. Seems to me
the 'Radio Shack' kind really did nothing. Was that the 'mutual
conductance' type? I see those for sale in the newgroups for $40 or
so every once in a while. My Pa-in-Law has a tester from his 1962 NRI
electronics school that takes all bases, but I have no idea what it
is actually testing. Haven't talked him out of it yet :) I've also
seen Hickock 5xx units (look very old) in a local antique mall booth,
usually for $30 to $40. What about these? Or is that just a waste
of time?
Does anyone have a basic tester for sale for my cataloging project? The tubes
I am going to catalog are all pretty standard types - only a few
4 and 5 pin types - the rest are typical BA types from the 50's and
50's.
Thanks for any advice and/or offers of testers for sale...
Dave WB7AWK
Tacoma, WA
Date: Wed, 03 Dec 1997 12:35:57 -0700
From: Dexter Francis <cwest@xmission.com>
Subject: Re: Tube tester advice
Dave -
For a top drawer engineering tester the Hickock 752B is hard to beat.
- - df
- ----------------------------------------------------
Need to Buy or Sell Tubes, Parts or BA Gear?
Visit our Web site at http://www.xmission.com/~cwest/
e-mail to: tubes@usa.net -or- cwest@xmission.com
P.O. Box 22443, Salt Lake City, Utah 84122
Date: Wed, 3 Dec 1997 15:57:38 EST
From: EWoodman <EWoodman@aol.com>
Subject: Big Caps
Anyone know where you might still be able to get those large oil-filled caps?
They ranged around 2 to 5uF or so and about 2 to 3kv. I need one for a
coupling cap in a sort of modified Heising modulation scheme.
Eric KA1YRV
Date: Wed, 3 Dec 1997 16:41:52 -0500
From: "Ornitz, Barry L" <ornitz@eastman.com>
Subject: RE: Tube tester advice
Dave, WB7AWK, asked about tube testers...
There are five basic types:
* Those that test filament continuity
* Those that test cathode emission
* Those that test mutual transconductance
* Those that test power output under actual conditions
* Special purpose bridges for precision measurement of all tube
parameters.
The first is rather obvious. If the filament is open, the tube won't
work. A vacuum tube voltmeter (VTVM), a volt-ohmmeter (VOM), or a
modern digital meter (DVM) used on a low resistance scale will do the
same thing if you have a tube basing diagram. These can tell you a tube
is bad, but not if a tube is good.
Emission testers are one step up. Typically all the grids of a tube are
tied to the plate and a voltage is applied. Cathode emission current is
measured. Again if a tube tests bad here, it IS bad. With rectifiers
(diodes), an emission test is a good indication of the tube performance.
With any other tube type, the readings are far less useful. Since
cathode emission does decline with age, the readings do tell you a
little. However, many tubes will test good on an emission tester, yet
have problems that will prevent the tube from performing properly.
A transconductance tester is probably the best instrument for testing
small receiving tubes. Such an instrument measures the change in plate
current for a small change in grid voltage (transconductance, or g(sub)m
as shown in most tube handbooks). The tube is measured under typical
"small signal" conditions with appropriate voltages on all electrodes.
The relative "Quality" of a tube can be measured by such a tester.
A power output tester is used for transmitting tubes and high-power
audio output tubes. The tube is operated under typical operating
conditions in such a tester, and the actual power output is measured.
These tend to be custom instruments, but they closely approximate the
results obtained by making measurements in the transmitter in which the
tubes are to be used.
Special purpose bridges are used in the laboratory to measure the plate
resistance, amplification factor, and transconductance(s) of a tube.
These are used in the design and prototype construction stages of a
vacuum tube. Like tube curve tracers, they have little use for the
average amateur radio operator. Curve tracers, by the way, dynamically
display the characteristic curves of a vacuum tube on an oscilloscope
screen. Spangenburg's book describes some of the special laboratory
testing methods.
Now having said all of this, the correct answer is that tube testers are
really seldom needed. I have two transconductance testers and one
emission tester. The transconductance testers are seldom used and the
emission tester is never used. A tester can come in handy when
screening a large number of tubes (as Dave wished to do), and they are
good for matching tubes (like parallel sweep tubes for transmitter
finals, or for push-pull audio applications). But the absolute best way
to test a tube is by substitution with a known good tube in your actual
circuit.
Allow me to repeat this... The best way to test is tube is by
substitution with a known good tube in you actual circuit. If the
problem goes away with the new tube, you have solved the problem.
But don't throw the tube away. It may be perfectly adequate for a less
critical application. Real "duds" should be discarded, of course, but
with the availability of new tubes declining rapidly, keeping marginal
tubes may not be a bad idea. Mark them as marginal, though, or you may
grab one thinking it is good!
As for the type of testers, Hickok is an old and respectable name. The
500 series of Hickok testers is almost the "gold standard" of testers -
especially for older tubes that have other than octal, 7-pin or 9-pin
standard bases. Several military testers are available that are just as
good. I am not very familiar with the model numbers and particular
features. I do know that a few of the military models have more meters
to measure all the individual parameters. With a good tube manual
giving the tube specifications, you can test a tube without having the
cookbook settings from a roll chart. All of these testers tend to be
physically big and heavy.
$30 to $40 sounds too low for good working Hickok testers. Remember the
socket pins of a tester take a beating in use as do the switches, etc.
Calibration of these older testers is sometimes difficult too as many
use copper oxide rectifiers that have characteristics not easily
duplicated with modern semiconductors (and FORGET about finding
replacements).
It is difficult for me to see spending $200 for a tube tester since they
are so seldom used or needed (unless you want to go into the tube buying
and selling business). Likewise a tube curve tracer is a fantastic
teaching tool (they were mainly sold to colleges for just this purpose),
but far too expensive and complicated for day-to-day troubleshooting.
[Semiconductor curve tracers are a different matter and I DO have one of
these.]
I know there will probably be quite different opinions from others
readers of your original question, and I am usually accused of telling
folks more than they really wanted to know, so judge this reply
accordingly. For my money, I would rather buy some really good books on
electronics theory to learn how circuits operate, than I would buy a
tube tester.
73, Barry L. Ornitz WA4VZQ ornitz@tricon.net
Date: Wed, 3 Dec 1997 17:26:02 -0500
From: "Robert g. Flory" <RobnPam@compuserve.com>
Subject: Copy of: Sick Tubes
- ---------- Forwarded Message ----------
From: Robert g. Flory, 104117,3104
TO: glowbugs, INTERNET:glowbugs@www.atl.com
CC: peter, INTERNET:peter_hutter@maca.sarnoff.com
DATE: 12/2/97 10:43
RE: Copy of: Sick Tubes
Hello Glowbugs,
My dad never did tell me how tubes went bad, and being just a kid license=
d
for 20 years, I only learned how tubes work, not how they fail.
I fired up my Drake T4xb on a load for the first time since I moved 6
months ago and was dissappointed to be only able to get 10-20 watts out o=
f
it. This is a rig I was using regularly since I had purchased it at a
hamfest last fall. I had put an out-of-the-box pair of Sylvania 6JB6 (n=
ot
the 6JB6A called for by Drake) in and they put out full power. =
I noticed that the resting plate current was low, so I attempted to adjus=
t
the bias, but could not get the resting plate current up to spec. I
checked the plate, screen, and filament voltages and all were ok.
I had a hard time accepting that the tubes could be bad, but having done
everything else I could think of, I switched one of the tubes and sure
enough I was able to get 1/2 power.
The tube I pulled out has a metallic-looking deposit on the inside of the=
top of the envelope. So does it's non-functional partner still in the ri=
g.
This is distinct from the gette on the side of the tubes. =
Earlier in the year, I turned the rig on to cook the moisture out of it,
having been rather humid this summer, and a plate supply rectifier shorte=
d,
without blowing the PS fuse quickly, since the genius I bought this rig
from had put a 20A fuse in it. Any connection with the loss of emission =
or
gain from the tubes?
What happened here? =
Rob, K2WI =
Date: Wed, 3 Dec 1997 20:32:10 -0500 (EST)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: My VT-4-C Hartley
>
> >Great! Last nite you had the misfortune to hear Grandma Hartley
> >at her worst. She had a sick padding capacitor on the tank,
> >and it wobbled a little when she sang and danced, giving her
> >a slight wobbulating song. I yanked out the bad cap and now
> >she has a fine T8.995 note. Alas, with a 211 in her belly,
> >she is right on the edge of where too much RF current circulates
> >in her tank, and the heating effects are shown as she drifts
> >about 200 cycles or so. Hint for the Hartley builders..... make
> >the tanks sturdier than you think they need to be, for nice stable
> >operation. At 20 watts input, I am pushing my BC-375 coil that
> >I use as her tank coil, slightly. On a 210 tube it is fine, but
> >the 211 is just on the edge.....
> >
> >Also, remember the cannonical 1929 style self-controlled oscillator
> >rule --- BUILD IT STURDY AND HEAVY. Overkill in all parts stats
> >and underkill in the running parameters makes for T9 notes.
> >
> >Hope you get your Hartley up and running for some fine seasonal
> >funzies.
> >
> >73/ZUT DE NA4G/Bob UP
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Bob, is there any peculiarities, eccentricities, or other phenomena
> that you found peculiar to the 211-based Hartley? Grid tap? Tuning
> condenser value? Anything at all? What voltage are you running on
> her? Etc., etc., etc.
Well, there are no real problems with 211's. They are BIG tubes,
with long element lengths and leads, and will drift some because
of element spacing being changed by heating under load.
Monkeying around with the grid resistors helps. I don't remember
offhand what Grandma has, but I think it is 15K at 50 watts.
The Grid cap is 100pf, but can be anything from around 100pf
to 1000pf, sized to prevent heating under current load.
Always used caps sized sufficiently to handle the current.
Squirrel city is guaranteed, if you dont. I like the old biggie
tub micas rated at 2-10 amps, when I can find them.
The grid tap is usually entirely non-critical in triodes. I start
at mid-point, adjust the grid resistor for suitable plate current
under loadout into a dummy load, and then maybe adjust the grid
tap +-1 turn, and compare to see if it is any better or worse.
Usually right in the middle works pretty well for me, and lower
powers of 25-33% max plate dissipation. Hartleys are not usually
that fussy.
I shoot for a padded total tuning capacitor to match a 12-15 turn
coil on 80M. That usually works out to around 500-700pf. I make
the tuning condenser around 100pf max and pad the rest. The antenna
coupling condenser is around 150pf on 80M.
Filament bypasses need to be 0.01 in my hands, although down to
0.002 will work.
On a 211, I would shoot for around 10 ohms per volt filament center
tap resistance, or around 100 ohms tapped at 50. Current rate for
10x the current or around 10 watts each side of tap or 20 watts total.
The RF choke should be sufficient to series resonate at 160M on 80M.
In the old days chokes were sometimes tuned to be electrical 1/4 waves.
I usually just grab up a whatever that looks around 1mh or more and
will handle the rated current x 5. If you wind your own, wind until
your conscience hurts.....around 300 turns on 80M on a 1 or 2 inch form
of maybe no. 22-26 wire for a '211, should do.
Key with a keying relay! The key can have upwards of 60% or more of
the plate voltage across it. Use a key thump filter, maybe around
1 henry and 1 to 4 ufd of capacity should do nicely. Size to handle
the current by a factor of 5 or so, intermittent service, and adjust
the capacity to suit your keying needs. Grandma uses 1 h and 4 ufd,
for rather soft keying (that is what you hear mostly when it keys).
Generally build everything like you were doing a 250-500 watter modern
amp, and it should do fine in 211 Hartley service. Smaller than
that is a little hard to tame, and may drift like Grandma Hartley
does.
I use a 450 volt MG set (old TCS dynamotor) to run Grandma, and it
works fine. Keying is done in the B- line to assure full shutoff
key up. On a 211, I would stick to around 700 volts max and no
more with optimally around 500. That is PLENTY.
Build all parts well mounted. The replacement cap I first put in
Grandma was mounted on a heavy silvered sheet copper strip, and it
wobbled as the keying relay actuated, even though the set was mounted
on rubber stoppers and had pig-tails for power leads to prevent
vibration transmission to the set. It is now firmly screwed to
the top of the main padder cap (big tub mica). Now she doesn't
wobble.
On tune up, use a small lamp, coupled to the series LC antenna primary
circuit. Resonate for maximum output on a FS meter and maximum
brilliance on a 25-60 watt or so incandescen lamp (they work JUST
FINE on 80M as dummy loads). Use no more than a 2 turn link if you
can, or wide spacing of the primary and secondary coils to prevent
overcoupling. Grandma now uses a two turn link at around 1 inch
of coupling for maximum output power, but I pay a slight drifting
price to push her to 20 watts on the 211. At 10 watts she is fine.
At 20, just beginning to drift. Once connected resonate for maximum
output on an FS meter or if you use such things 1:1 swr on whatever
coupling device you might use. In my hands 1:1 is always max output
on the FS meter (old sparks trick from my OM who used it for some 50
or more years professionally, and only used an SWR meter in his final
years, once in a while). The FS meter always peaks on maximum power
transfer to the load, and that is always the point to shoot for.
If you get a double peak on tuning the antenna circuit, you are way
overcoupled beyond critical coupling. Uncouple. If you get large
frequency excursions.....Uncouple. And, always monitor your keying
in a ``growler'' of some sort (a monitor device/receiver/meter/whatever)
that actually lets you HEAR your emitted signal without overloading).
> Rod, N5HV
> w5hvv@aeneas.net
>
> P.S. I enjoyed our chat last night. I thought she sounded great!
Mee too. I could hear her wobulating, but now she is much better.
I still need to cure the slow drift with the big 211 bottle.
That is all I can think of, offhand, but others will be able to add
their experiences, and fill in the holes.
Remember, just be SAFE around these things.
Bob/NA4G
Date: Thu, 4 Dec 1997 10:48:16 -0500 (EST)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: My VT-4-C Hartley
> BOB, I HAVE FOUR OLD TRANSMITTING MICAS THAT ARE 98 TO 100 UUFD EACH.
> I'LL USE ONE FOR THE GRID COUPLING CAP AND THE THE OTHER THREE FOR
> PADDING THE TUNING CONDENSER.. ER, CAPACITOR.
They should do fine. That I what I use (sounds like pulls from BC-375
TU-5 tuning units, to me, where they were used for padders also).
> BOB, IF I CAN GET A CENTER-TAPPED 10 VCT TRANSFORMER, CAN'T I DO AWAY
> WITH THE NEED FOR THE FILAMENT CENTER TAP RESISTANCE?
If the cathode is grounded and you key the B- line, yes. If the
cathode is grounded and you key by grid biasing, yes. If you need
to key the cathode, then you need a center tap of some kind.
I prefer the resistor or lamp method as opposed to the transformer
center tap method, since I often power sets from batteries, and would
lose the center tap then.
> >Key with a keying relay! The key can have upwards of 60% or more of
> >the plate voltage across it.
>
> I'LL SEE IF I CAN GET A MERCURY WETTED 12 VOLT RELAY FOR THAT!
That will probably work, although make sure it has sufficient current
rating to handle the load of the key thump filter. The inductive
kick load is quite high in B- keying with a 1 henry choke/1-4 ufd cap.
Cathode keying would have a similar kick.
Small relays will stick on the contacts, quite readily, if you are
not careful. The big mercury wetted contactors for 110vac line use,
work fine, though. If the relay has contacts around 3/16 inch or
larger that is probably fine. It only needs to key around 20wpm or
so, for most folks, although if you put a jumpstart capacitor of a
few ufd across the relay to hold a starting kick charge, you can
get bulky slow relays to key quite well at moderately fast speeds.
Grandma Hartley's relay has a 10ufd cap across the relay coil to
store charge between dits and it keeps the relay from lagging at QRQ.
Bob/NA4G
Date: Thu, 4 Dec 1997 10:51:45 -0600
From: "Freeberg, Scott (STP)" <scott.freeberg@guidant.com>
Subject: NA4G, Is MIME Turned OFF?
Bob NA4G,
Please Bear with me here. Is the MIME format turned off now? Is the
message good with no extra MIME garbage being sent with this text? I am
sending this to you through the listserve to see if the MIME / Listserve
problem has been resolved.
Thanks,
Scott WA9WFA St. Paul Minn
Attachment Converted: "c:\eudora32\Attach\winmail22.dat"
Date: Tue, 09 Dec 1997 11:21:48 -0600
From: Conard Murray <cfm5723@tntech.edu>
Subject: Hello 1 2 3 4 5
Test ....
Conard
End of glowbugs V1 #202
***********************