S.E.X 2.1 voltage check issue

[mcwhart]

Hello,

New to the forum.  Just finished assembling a S.E.X. 2.1 kit.  The resistance check was good, but when I did a voltage check I found the following discrepancies:

One Tube not on.  Reversed tubes to verify that both were functional.

Terminal 11 voltage OK, terminal 21 measures 440 instead of 380
Terminal 15 voltage OK, terminal 25 measures 0 instead of 19
Terminal A2 voltage OK, terminal B2 measures 445 instead of 375
Terminal A3 voltage OK, terminal B3 measures 0 instead of 19
Terminal A5 voltage OK, terminal B5 measures 400 instead of 75
Terminal A6 voltage OK, terminal B6 measures 0 instead of 2.5

Everything else seems to measure OK.  Any suggestions?

Thank you for your help!

[Grainger49]

Without a heater you will get high voltage on the plate and low voltage on the cathode.  So this accounts for one side's readings.  You need to check for the AC DC voltage on the heaters.

 I am at work so I can't tell you what the tube pins are.  The schematic will have the tube pin numbers for the heaters.  You should have about 6.3V across the heaters, IIRC.

[mcwhart]

Thanks for the information.  I am unfortunately not very tube electronics literate, but in looking at the schematic it seems that the heater pins are #7 and #8.  What does IIRC stand for? 

If I do not have the 6.3V measurement across the heaters, where should I be looking?

Thanks again

"I am at work so I can't tell you what the tube pins are.  The schematic will have the tube pin numbers for the heaters.  You should have about 6.3V across the heaters, IIRC."

[mcwhart]

Oh, got it....IIRC=if I recall correctly.


I may have been wrong about the heater pins.  Looking at the schematic again and the voltage you suggested, it looks as though they may be pins 4 and 5.  Again, sorry for my lack of experience. 

[Grainger49]

Yes, that is right.

Still, try to measure between tube pins 7 & 8 on each tube.  Be careful that you don't short them together.

[Paul Birkeland]

Yes, you are looking at the voltage between pins 7 and 8 on each tube.  This will be a DC voltage that should be between 5.8 and 6.3V.

If it's easier, you can ground one meter probe and measure each pin separately.  You will get something like +3/-3, but not quite that well matched. 

If neither tube will glow when plugged into one of the sockets, that's likely the issue.  It's also a good idea to be sure that the little guide slot that aligns the tube in the socket is oriented correctly.