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2359glenn | studio - Page 250

post #3736 of 11805
Quote:
Originally Posted by Ultrainferno View Post
And what if the gz series isnt in the manual tongue.gif

Then you will have to come to San Francisco and I'll test the tubes for you. ;)

 

Listening to my GlennMonoMonos!

They are wonderful this Saturday afternoon!

And they are packing the Brimar 5Z4G with bullet holes.

Double your pleasure, double your fun!


Edited by Clayton SF - 7/13/13 at 4:04pm
post #3737 of 11805
jealous!
post #3738 of 11805
Quote:
Originally Posted by rosgr63 View Post

Tube rolling has started, testing 3 different RSD 6SN7 in the driver position, 3DG4 rectifier, 6 6BL7 as outputs driving AKG K701.

 

Listening to Roy Hamilton, Unchained Melody.


You might have to switch to 6336 outputs if you try the K1000s should give enough power for them?

post #3739 of 11805
Quote:
Originally Posted by Ultrainferno View Post
jealous!

Are you still up? Ultra-!

post #3740 of 11805
Quote:
Originally Posted by Clayton SF View Post

Are you still up? Ultra-!
Just got home. Fueled up with Carlsberg. Now a late night snack and then time for bed. Dreaming of amps and cookies. Mmm cookies
post #3741 of 11805

The tester Clayton showed you is very easy to use.

 

If the test settings are not in the manual then you can't test the tube.

Sometimes there are extra test data sheets which a seller may have.

 

Most important is to have the right types of sockets and filament voltages.

 

Some tubes like the 596 you'll have to test with an adapter.

post #3742 of 11805
Quote:
Originally Posted by rosgr63 View Post

The tester Clayton showed you is very easy to use.

 

If the test settings are not in the manual then you can't test the tube.

Sometimes there are extra test data sheets which a seller may have.

 

Most important is to have the right types of sockets and filament voltages.

 

Some tubes like the 596 you'll have to test with an adapter.

 

I test a lot of tubes that aren't in the book, including the 596 and the GZ37.  If the pin outs are the same and the tube is a replacement for another, I just use that tube's settings.  In the end, you just want to make sure there aren't any shorts or electrical problems.

 

Do others feels differently?

post #3743 of 11805

I think a lot of people do this.  This is my suspicion about why some sellers put weak 5998 tubes out the door, because they were testing them as a 6AS7G.  The 5998 has more than twice the transconductance so testing strong by 6AS7 standards meant the tube could actually be weak.

 

Shorts and leaks is definitely the most important testing, people pay too much attention to emission.  As long as the tube functions in the circuit and doesn't sound bad it's fine after it passes the short/leak test.

post #3744 of 11805

Exactly.  I am not testing them for sale. 

post #3745 of 11805

I have been very tempted to buy the Jackson 648S that Bob has for sale right now.  It's a beautiful tester, but I'm worried it might be "too much" tester for a first time owner like me and the shorts testing is not as sensitive as it could be.  Love the fact that it tests all tube types.  I will need to test 45 tubes and lots of more modern testers don't have that 4-pin socket.  I'm not sure what to do........

post #3746 of 11805

I bought one from Bob a couple months ago and that's all I use now.  

post #3747 of 11805
The good Stavros is looking for one for me. We're looking at TV-7.
post #3748 of 11805

Here is some excellent advice from Bob Putnak

 

If you want a nutshell summary, I find room for both machines.
TV-7 pros:
- better test method for amplifying tubes
- military build quality
- highly respected by everyone, although that may be due to it simply being a military product and the military always used "quality"
- grid leakage test is better than the Jackson, although still inferior to a few other testers that excel in that *1* area, but are inferior otherwise.

Jackson pros:
- substantially better rectifier test
- better life test
- model S, which I recommended, has a full socket config of 4-pin thru 12-pin compactron.
- damn near maintenance-free 

Less-than-ideal aspects:
- neither has a great leakage test

- the TV-7 shorts test is very limited -- this applies to all Hickok's too.  The Jackson shorts test is OK but not foolproof.  

- the high AC fields generated by the Jackson can sometimes skew readings of high-mu tubes, such as 7868 or 7591.  Generally this is easy to spot because if you cup the tube with your hand and the reading changes, you are seeing oscillation, but that may not always be evident.  Oscillation is a issue with all tube testers to some degree, and yet ANOTHER problem that makes "tube testing" an art and NOT a science.  The S model is better than earlier models at suppressing oscillation.

- the Jackson test method does not "prove" that a tube is capable of amplification.  That sounds worse in theory than reality.  The Jackson test method proves that the tube can supply the plate current that is necessary to operate a typical circuit that uses that tube.  That is very useful, and it does factor in the control grid and does use high potentials on the plate and screen.  That is not the same as supplying a test signal and amplifying it, which is what a Gm tester does.  And the end of the day, it seldom makes a difference in "tube testing" as the Jackson is great at finding bad tubes.  In the rare situation that the tube would pass a Jackson test but not actually amplify -- a situation that I have NEVER encountered in 20 years -- any novice tech should be able to find that the signal stops at the tube's plate circuit, thereby indicating a tube change was necessary.

In reality, regardless of tube tester, you will find a number of tubes that PASS your tube tester(s) and work SUBSTANDARD (or outright fail) IN-CIRCUIT, and you will find that many tubes you REJECT as "bad" or "weak" would work FINE in circuit if you had actually tried them.  That will ALWAYS be a FACT.

post #3749 of 11805

That's very helpful, thanks for sharing that.

post #3750 of 11805

In our discussions with Bob and Glenn also agrees, we have concluded that the best and final test is in circuit.

 

I only test tubes for which I have set up data and strictly equivalent tubes.

I have 8 testers so between them there is a good chance I can find what I need.

 

My daily work horses are a Jackson 648 and a Philco 9100 with a plate current mod.

 

Xcalibur the Jackson is a good tester but the TV 7 is a step above as it measures transconductance, robust and very well made, but more expensive.

 

The critical factor is to get a tester that has been rebuilt, as most resistors will have drifted by now.

 

Finally a tube can operate in circuit at a different point than the one tested in the tester and could fail even if it has passed all the tests even the 100 Khz leakage test the Sencore/B&K/Mercury use.

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