Hello,

What does it mean when a tube pegs the meter on a tube tester. I have a
pair of 6SN7 tubes that I have tested on a calibrated TV-7D/U tube tester,
and each triode test at about 90-94 except one.........it pegs the meter.
Is this tube good to use?

Thanks,
Kelly

What does it mean when a tube pegs the meter on a tube tester.
I have a pair of 6SN7 tubes that I have tested on a calibrated
TV-7D/U tube tester, and each triode test at about 90-94
except one... it pegs the meter. Is this tube good to use?

"This tube goes all the way to 11!"

Assuming it's an emissions-type tester, one of the tube's elements is probably
shorted to the cathode.

KSM wrote:

Hello,

What does it mean when a tube pegs the meter on a tube tester. I have a
pair of 6SN7 tubes that I have tested on a calibrated TV-7D/U tube tester,
and each triode test at about 90-94 except one.........it pegs the meter.
Is this tube good to use?

Thanks,
Kelly

It probably has a short between two of the elements. I'd be extremely
cautious about using the tube, unless it was in a circuit that was
self-limiting (i.e. high enough plate resistance) to prevent excessive
current from flowing. Even then I'd take some careful measurements and
keep a close eye on it.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

wouldn't a short between elements have already shown up on the shorting test
(that's the first step on my AVO 3)?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Andy Evans wrote:
wouldn't a short between elements have already shown up on the shorting test
(that's the first step on my AVO 3)?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

I don't know about AVO's, but on my B&K 747B I have run into the
occasional tube that pegs the meter without displaying a short on the
little neon lamp "short" tester (and also doesn't work as expected in
circuit). Maybe it's a question of *degree*, or perhaps some shorts only
show up at higher voltages. Not sure. ::shrug::

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

on my TV-7D/U it test good with no shorts (on short test).
"Fred Nachbaur" wrote in message
news:TCdmc.2534$uN4.254@clgrps12...


Andy Evans wrote:
wouldn't a short between elements have already shown up on the shorting
test
(that's the first step on my AVO 3)?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

I don't know about AVO's, but on my B&K 747B I have run into the
occasional tube that pegs the meter without displaying a short on the
little neon lamp "short" tester (and also doesn't work as expected in
circuit). Maybe it's a question of *degree*, or perhaps some shorts only
show up at higher voltages. Not sure. ::shrug::

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

KSM wrote:
on my TV-7D/U it test good with no shorts (on short test).

It would be interesting to see if it is, indeed, merely a particularly
"hot" 6SN7. The only way to do this reliably would be to do some
in-circuit measurements of gain and operating point, referenced to a
"bogey" tube that reads close to 100% on your tester.

It would ideally be in a common-cathode circuit with no local feedback
(unbypassed cathode resistor), as a circuit with feedback or a voltage
follower would give erroneous results.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

Kelly,

It has been my experience that tubes that are slightly gassy can exhibit
high GM readings without any shorts.

My money is on 'gas'.

Carroll
"KSM" wrote in message
ink.net...
Hello,

What does it mean when a tube pegs the meter on a tube tester. I have a
pair of 6SN7 tubes that I have tested on a calibrated TV-7D/U tube tester,
and each triode test at about 90-94 except one.........it pegs the meter.
Is this tube good to use?

Thanks,
Kelly

Fred Nachbaur wrote in message news:Qovmc.27021$U75.21311@edtnps89...
KSM wrote:
on my TV-7D/U it test good with no shorts (on short test).

It would be interesting to see if it is, indeed, merely a particularly
"hot" 6SN7. The only way to do this reliably would be to do some
in-circuit measurements of gain and operating point, referenced to a
"bogey" tube that reads close to 100% on your tester.

It would ideally be in a common-cathode circuit with no local feedback
(unbypassed cathode resistor), as a circuit with feedback or a voltage
follower would give erroneous results.

Cheers,
Fred


I have a bunch of 6V6's that ping the needle on my Eico 667
tester.They seem fine otherwise,and the handfull that I was playing
with in a couple amps all worked fine.I suppose they could be a little
gassy,I think they are all somewhat used tubes,pulled from old amps
and radios,but they're still kickin! ;-)
Hmm,I have noticed that this tester is kinda "funny" with certain
tubes,maybe the settings I have are incorrect?

On Wed, 05 May 2004 20:23:06 +0000, KSM wrote:

Hello,

What does it mean when a tube pegs the meter on a tube tester. I have a
pair of 6SN7 tubes that I have tested on a calibrated TV-7D/U tube tester,
and each triode test at about 90-94 except one.........it pegs the meter.
Is this tube good to use?

Thanks,
Kelly

Turn the bias control up a hair and see if the needle
comes back into range where you can read it.
If so, it should be OK, if it just keeps pegging the
meter even with the bias turned up, it's shorted.

The setting on a TV7 has the 6SN7 & 6CG7's reading fairly
high on the meter so it's not terribly unusual for a few
out of a batch to peg the meter.


--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com

"Ned Carlson" wrote in message ...

The setting on a TV7 has the 6SN7 & 6CG7's reading fairly
high on the meter so it's not terribly unusual for a few
out of a batch to peg the meter.

Perhaps so, but I'd be damned careful about retesting it with the bias
up just a bit - assuming it passed for shorts first while being
tapped, I'd open the bias all the way up & barely use the test button
for the shortest possible indication, to see if it wanted to peg
again, if I didn't just forget it & chuck it. TV7 meters are quick to
toast, hard to find, harder to repair and expensive if one is lucky.
6SN7's are plentiful & cheap. Pegging a TV7 meter is a high-risk
proposition and it is wise to throw a couple of $0.02 1N4007's across
it for a teeny bit of (not foolproof) protection.

wrote in message

...... TV7 meters are quick to
toast, hard to find, harder to repair and expensive if one is lucky.
6SN7's are plentiful & cheap. Pegging a TV7 meter is a high-risk
proposition and it is wise to throw a couple of $0.02 1N4007's across
it for a teeny bit of (not foolproof) protection.
================================================== ===

Those who have "toasted" meters in their TV-7s can effect a simple cure by going to:

http://www.gvtc.com/~edengel/TARC.htm

then clicking on the "TV-7 Meter Replacement" article.


Best Regards,

Ed Engelken
Canyon Lake, TX

On Sat, 08 May 2004 14:01:51 +0000, lbrty4u wrote:

"Ned Carlson" wrote in message
...

The setting on a TV7 has the 6SN7 & 6CG7's reading fairly high on the
meter so it's not terribly unusual for a few out of a batch to peg the
meter.

Perhaps so, but I'd be damned careful about retesting it with the bias up
just a bit - assuming it passed for shorts first while being tapped, I'd
open the bias all the way up & barely use the test button for the shortest
possible indication, to see if it wanted to peg again, if I didn't just
forget it & chuck it.

A good 6SN7 reads way over to the right on a TV7 (the minimum
is 50) the way it is, so it's certainly possible a few really
hot ones would peg the meter, since that's nearly within
tolerance of what a good one would test. Otherwise I wouldn't
have made the suggestion.

If this were, say,a 12AX7 or 5U4 we were talking about,
which normally read quite a bit lower, I'd assume anything
that pegs the meter was shorted, since that's so high as
to be abnormal.

IIRC, the short light on a TV7 won't light up unless the
short is something like 250K ohms or less, and shorts
of a much higher resistance can cause a tube not to work
properly in circuit.



--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com

(Nothing40) wrote in message . com...
I have a bunch of 6V6's that ping the needle on my Eico 667
tester.They seem fine otherwise,and the handfull that I was playing
with in a couple amps all worked fine.I suppose they could be a little
gassy,I think they are all somewhat used tubes,pulled from old amps
and radios,but they're still kickin! ;-)
Hmm,I have noticed that this tester is kinda "funny" with certain
tubes,maybe the settings I have are incorrect?

The data charts for the Eico 667, 666, and Simpson 1000, which are
compatible, all have different listings and give different "merit"
readings for the same 6V6 tubes I tested. The E667 & E666 1-1-78
listing (6.3 40,40 6143562111 4,2 3-4-5-8 3) gives the highest
readings, (122 on a GE 6V6 nos, for example). The E666-04&-05 listing
(6.3 21,98 124451111 4,1 3-4-5-8 3) gives a medium reading of 95. The
Simpson Nov.1960 6V6 listing (6.3 70,87 124351111 4,1 3-4-5-8
3;converted to Eico-ese) gives the lowest merit reading of 81 for the
same tube. Even though the Eico 667 charts were the newest data, they
weren't as good for some tube types as the older E666 and Simpson 1000
charts, based on my experience. All of the Eico charts suffer from the
occasional, gross typographical errors; that in some cases can stress
or destroy a good tube. Before testing a tube type for the first time,
I check the handbook values to be sure that the tester switch settings
make sense. "Kinda Funny" (your terminology) doesn't exactly describe
the feeling when an Eico chart listing with a major typo. error
destroys an expensive tube.