How to test a tube

[ger56]

hello

I need to repair a non working sansui au111 and want first to check if the tubes are working or not .
Do not know how to test at least if tehy work or not ?
I leave in Casablanca so I can't go to a specialised workshop .

Thank for help
Ger56

[PRR]

If it does not work at all, the power supply is bad.

The power supply is simple. You should have HIGH VOLTAGE A.C. on one side of the rectifier tube, HIGH VOLTAGE D.C. on the other side. Figure out which tube is the rectifier (it might not have a tube rectifier) and look-up the pin connections. And be careful.

[ger56]

Well the power suppply is ok but it won(t start as some resistor and do on are missing .

I have to check everything, change the bad resistor , most of caps should be changed but do not know how to check the tube to see what has to be replaced this is my problem by now .

ger56

[Yvesm]

Hi !

Yes tubes may be bad .. or may be not !
Testing tubes outside your amp means using a tube tester, and if you have not, it's simpler to check voltages against the schematic.

Here is what I've found about Sansui AU111:
http://www.bonavolta.ch/hobby/fr/audio/sansui.htm

If this can help ....

Does the tube glows ?
If not, what is voltage at pins 4, 5 and 9 ?

What is the voltage at the tube's anode ?

... just to start ...

Yves.

[ger56]

Thank you yves

In fact I am french from Paris .

I will check the output once I change the resistor and others in order to start .

In fact I have the schematic for the amp!

Just wanted to know if there is a way to test tube without havig a tube tester ? continuity or something like .

Regards

Gerard

[JDeV]

The question have been asked earlier, but I could not find a clear answer:

Are there any method to test a tube without a tube tester, any of the parameters?

I am bussy repairing an old stereo Sansui radio/amp combo, using ECL82 tubes. The 1 old set of tubes I got , work well on both channels. I bought another set, which turned bright orange after 3 minutes. Took back to tube guy and exchanged for another "new" set. Now I notice a blue glow between the plates of both new tubes. All voltages compares correct to the service manual.

Any suggestions on this problem and tube testing?

[karma]

the new set turned bright orange because everytime you replace tubes u must bios the amp. blue glow is fine gassy tubes or new tubes do that.

if you wana test tubes get a tube tester. just one of manny


http://cgi.ebay.ca/LAFAYETTE-TE-55-T...QQcmdZViewItem

[anatech]

Normal failure in a tube creates lower to no current flow. Odd times elements may short, but the plate will have burn or "cook" marks on it. The best way to check a tube is in circuit and measure the terminal voltages.
Other parts will get you more often. Coupling caps are prime here. Run the unit up with no tubes (except rectifier) to about 70% ac voltage. The grids should measure 0V. Some power tubes are biased with a negative voltage. Some regulators "float" at some positive voltage.

With negative supplies for outputs, look at the ripple. There should be none.

-Chris

[JDeV]

if you wana test tubes get a tube tester. just one of manny

http://cgi.ebay.ca/LAFAYETTE-TE-55-T...QQcmdZViewItem

How about this, anybody got expereince with it / build and used it??

Build your own