Preamp tube testing, with vintage tube tester. Question.

DJJazzV · #1 12-23-2011, 05:54 PM

I just purchased a somewhat vintage (1970) B&K Dyna Jet 606 tube tester. Just for basic tube testing. Seems to work great. I've been testing mostly preamp tubes, but a few power tubes as well. Great success, and lots of fun, except I've noticed that most of the "new production" preamp tubes don't pass the test. They stay in the "replace" field. Some are even brand new as I bought them today. All of my vintage RCA, GE, Telefunken, Sylvania, Jan/Philips, Siemans, etc, all pass as "Good". Somewhere between 80 and 105. Some NOS, and some used.

The preamp tubes in question are 12AX7, 12AU7, and 12AT7. Only 2 new production brands got into the "Good" area so far. Could I be doing something wrong? Is a vintage tube tester not an accurate tester for new production preamp tubes?

2 different sets of new production power tubes both passed without a problem. I'm just finding it very odd that most of the new production preamp tubes didn't pass on the vintage tester. It has to be me or the tester, right?

**B-string** · #2 12-23-2011, 06:00 PM

Check the socket on the tester for spread sockets. New production tubes can have thinner pins and they may not be making good contact in the tester.

Spectrum · #3 12-23-2011, 06:02 PM

No pic, no tube tester!

Is this the kind of tube tester my dad used to take me to use in the drug store, or is it more portable? He would take all the tubes out of the TV and we'd test them all to see if we could fix the thing without calling a TV repairman.

Mr. Foxen · #4 12-23-2011, 06:20 PM

Think they need to be calibrated and checked for drifting components. But saying modern pre tubes suck is fair.

DJJazzV · #5 12-23-2011, 06:21 PM

Quote:

Originally Posted by B-string

Check the socket on the tester for spread sockets. New production tubes can have thinner pins and they may not be making good contact in the tester.

The socket seems fine, and I don't notice any difference in the pins on the new and old tubes. I even tried some new production tubes with the gold plated pins. Same results. They end up somewhere near the middle of "replace".

Quote:

Originally Posted by Spectrum

No pic, no tube tester!

Is this the kind of tube tester my dad used to take me to use in the drug store, or is it more portable? He would take all the tubes out of the TV and we'd test them all to see if we could fix the thing without calling a TV repairman.

I tried to get one of those drug store testers! How cool would that be! Wife thought it would ugly in the basement. I should have bought it anyway.

This tester is a small portable one. All I need is basic testing, and so far, it's very cool. It tells me ratings for "Replace" & "Good", and checks for "Grid Emission".

warnergt · #6 12-23-2011, 07:31 PM

I have a vintage tube tester, too. They just don't give a reliable
reading. The problem is that the tube tester is, in essence,
performing a D.C. test. All tubes are not alike when used as
D.C. devices and it doesn't matter because most circuits use
some sort of biasing (e.g. resistors in the cathode circuit) to
compensate for the D.C. differences.

What is important is how the tube performs in an A.C. circuit.
I don't know of an inexpensive tester that can test this.

staindbass · #7 12-23-2011, 09:54 PM

i have a bunch of tube testers, heathkit , b&k, refurbished hickok tv-7u, hickok 752a. i also noticed alot of the new modern groove tubes and chinese preamp tubes you mentioned measure horribly compared to good vintage ones. many are just barely at minimum usage point. you could argue that the tester is out of spec, but if it were, nos telefunkens from the 50's wouldent be measuring way higher. if the pins were too small,and werent making contact i figure they wouldent show a measurement at all, so its a mystery to me.

DJJazzV · #8 12-25-2011, 04:16 PM

That's exactly how I feel. It's a "mystery" to me. I tested about 30 vintage 12AX7, 12AU7, & 12AT7 tubes. 2 stayed in the "replace" mode on the tester, and 2 had "Grid Emission" issues. Those 4 got tossed.
I tested 8 "new production" tubes of various brands, and only 2 made it into the "Good" reading, and none had a "Grid Emission" issue.
1. Because of my testing, I've only installed vintage tubes that tested the highest into an Ampeg B-15R amp and an Aguilar DB680 preamp so far.
2. Because of #1, perhaps they aren't a great fit since those 2 amps are "newer", so they would have been built and based on "new production" tubes.
3. I don't have any vintage power amp tubes to test, but I tested 8 "new production" tubes, and they all passed easily.

Bottom line: I'm having fun tube testing & swapping, the amps sound great, and I know all the tubes currently installed passed the tube tester testing, so why worry?
Tubes are fun!

Quote:

Originally Posted by staindbass

i have a bunch of tube testers, heathkit , b&k, refurbished hickok tv-7u, hickok 752a. i also noticed alot of the new modern groove tubes and chinese preamp tubes you mentioned measure horribly compared to good vintage ones. many are just barely at minimum usage point. you could argue that the tester is out of spec, but if it were, nos telefunkens from the 50's wouldent be measuring way higher. if the pins were too small,and werent making contact i figure they wouldent show a measurement at all, so its a mystery to me.

**B-string** · #9 12-25-2011, 05:23 PM

Keep in mind the only best tube tester is the circuit it will be used in. Grid emission, grid leakage and Gm testers are not infallible but are used as a guide. Don't forget short tests, those are pretty reliable.

bongomania · #10 12-25-2011, 05:33 PM

Must read (and ignore the silly graphics): Tales From The Tone Lounge; The Idiot's Guide To TubeTesters!

JimmyM · #11 12-25-2011, 06:19 PM

Quote:

Originally Posted by DJJazzV

1. Because of my testing, I've only installed vintage tubes that tested the highest into an Ampeg B-15R amp and an Aguilar DB680 preamp so far.
2. Because of #1, perhaps they aren't a great fit since those 2 amps are "newer", so they would have been built and based on "new production" tubes.

The only time I've ever heard of a circuit being designed around new tubes where the performance is affected if you use NOS tubes is in the Mesa 400+. Don't know about the Aggie, but I'd stick with NOS in the B-15R for sure. Justim Meldal-Johnsen felt his improved greatly with NOS tubes in it.

DJJazzV · #12 01-01-2012, 05:33 PM

Jimmy,
Thank you very much for the information. Thanks to you, I just searched the JMJ thread, and also found that he disconnected the tweeter on the B-15R. So.... I just did the same. Nice!
Back to "tube-rolling" again.

Cheers!

Quote:

Originally Posted by JimmyM

The only time I've ever heard of a circuit being designed around new tubes where the performance is affected if you use NOS tubes is in the Mesa 400+. Don't know about the Aggie, but I'd stick with NOS in the B-15R for sure. Justim Meldal-Johnsen felt his improved greatly with NOS tubes in it.