| Author |
Topic: Tube testing Question |
Richard Tipple
From:
Ohio, USA
|
Posted 12 Feb 2010 9:55 am |
|
Since Im not a tube guru  thought I would ask..
Can tubes be tested to see if they need replaced ,or are wearing out.
Im thinking of replacing the tubes in my Revelation.
I purchased the Rev used from a formite. Its an older model so Im not sure how old the tubes are.
I guess I dont want to replace the tubes if the old ones are still in good shape,, I just assume they might be a little weak  |
|
|
 |
Jack Stoner
From:
Kansas City, MO
|
Posted 12 Feb 2010 11:44 am
|
|
A mutual conductance type tube tester can give some idea of how good the tubes are but even that doesn't test them under actual circuit (voltages) conditions. A mutual conductance is good for matching tubes.
There are also cathode emission testers and they don't do much at all.
The best tube tester is to replace the tube(s) with new ones. |
|
|
|
Ray Thomas
From:
Goldsboro North Carolina
|
Posted 13 Feb 2010 2:26 pm Tube Testers
|
|
| Richard, having been in the electronic repair business just about all my life (75 now) I agree with Jack, testers might help a little if a tube is very weak or dead but they will not duplicate what the tube has to do in the circuit. Go with the substitution method and sometimes you might need to sub the new one. |
|
|
|
Jay Fagerlie
From:
Lotus, California, USA
|
Posted 13 Feb 2010 4:11 pm
|
|
Keep in mind that pre amp tubes can last for many many years. A few years of use doesn't mean they are ready for replacement automatically.
Some of my favorite tubes are from the 50's and 60's and sound flat out better than most of what is available new these days...
Swapping out is a good way to not only check for operation, but is also a great way to audition different tubes for a different sound
Different manufacturers tubes do sound different.
If you can get your hands on some, try Mullard or Telefunken....some of the old RCA's sound great....
You don't need to get NOS either-used tubes are definitely worth trying.
IMHO, of the current production tubes, JJ's are good sounding tubes, and not too hard on the wallet.
Jay |
|
|
|
Al Szwarc
From:
Metuchen, New Jersey, USA * R.I.P.
|
Posted 15 Feb 2010 9:18 am Tube testing
|
|
| I agree with all of the above and add a word of caution. People find tube testers in garage sales flea markets etc. What could be called the secondary junk market. If you find one of these you should take it to a tech to have it checked. Without calibration or a checkup, it is worthless as a tool for testing anything more than your nerves. al |
|
|
|
Jay Fagerlie
From:
Lotus, California, USA
|
Posted 15 Feb 2010 6:49 pm
|
|
Good point Al.
I've been working with tubes and tube circuits for almost 30 years now and can count on one hand the amount of times I've used a tube tester.
I've only used them to verify a shorted tube, that's about all they are good for.
A well designed, properly functioning tube circuit is all that is really needed to check the operation of a tube.
Most guitar tube amps work great as a 'tube tester'.
The easiest way to check for a noisy tube is to put it into a high gain guitar amp and give it a listen.
All tube amps these days have a resistor across the input to keep the tube loaded when an instrument is not plugged in-perfect test bed to check tubes!
Grab a hand full of tubes, make sure to turn off the amp when swapping them out, and give it a try.
You too can evaluate your tubes!!!
This only goes for pre amp tubes-power amp tubes are best left for the tech to take care of.
Jay |
|
|
|
Jack Stoner
From:
Kansas City, MO
|
Posted 16 Feb 2010 4:00 am
|
|
Microphonic tubes are another problem. Usually a light "tap" on the tube and if it's noisy it will produce a noise when tapped.
My electronics/Tube experience go back to 1955 when I was in Radio Operator school in the Air Force. I got my first Ham Radio license in 1960 (W5DVO) and my 2nd Class FCC Radio Telephone in 1963. |
|
|
|
