Tube not glowing

[benz]

Help! i have done soldering my crack and went to turn on the power and check if the tubes are glowing.
Turns out one side of the 12AU7 is not glowing.
Can anyone tell me what could be the problem?

 

[Grainger49]

First you should do a resistance test.  If you have completed that then you should touch up the solder joints for the heaters.  If the 6080 is glowing then the solder joints there (the ones that form the jumpers to the 12AU7) might be bad and the solder joints on the 12AU7 might be bad.

The tube socket is new, but may be old.  The tube is new, old stock.  So try removing and re-inserting the tube a dozen times to get the socket and tube pins cleaned (not the best cleaning but cleans surprisingly well).

Try those and report back.

 

[benz]

Ok thanks for replying. Just one question does the wires in terminal B8L and B7L need to be soldered? I did not solder them cause it's not mention in the manual. Just wondering if that is necessary.

 

[hjc]

Just one question does the wires in terminal B8L and B7L need to be soldered? I did not solder them cause it's not mention in the manual.

You're right, the manual doesn't say to solder them. I think that will be your problem

 

[benz]

Ok i have solder the wires and the both sides of the tube are glowing now. However when i did my voltage check some of the reading measurements are wrong. Some of the readings are too high and i can't get any voltage reading from terminal A9 and B7. Any idea why?

 

[benz]

This are mine voltage readings:
1-75-90 (148)
2- 170 (166)
3- 0 (0)
4- 170 (166)
5- 75-90 (92)
6- 0 (?)
7- 100 (148)
8- 0 (0)
9- 100 (110)
10- 0 (?)
11- 0 (0)
12- 0 (-12.6)
13- 170 (166)
14- 0 (-11.6)
15- 185 (190)
20- 0 (-11.2)
21- 206 (215)
A1- 90 (91)
A2- 0 (1.568)
A4- 0 (0)
A5- 0 (0)
A6- 90 (149)
A7- 0 (-17)
A9- 0 (?)
B1- 90 (149)
B2- 170 (166)
B3- 100 (148)
B4- 90 (92)
B5- 170 (166)
B6- 100 (111)
B7- 0 (?)
B9- 0 (0.1)
Those that are ? i could not get any readings from the multimeter or some of the readings keep changing and i can't get a proper reading. I am new to this kind of thing so i may not understand  what is going on. Any advice on how to proceed from here?

 

[Paul Birkeland]

[size=12pt]
T1 and T5 should be connected to each other and therefore must have the same voltage on them.

No, this is incorrect.

B1 and B3 are the result of that half of the tube not turning on. 

This is also incorrect.  B1 and B3 are a result of half the 12AU7 not conducting.

Are you 100% sure both halves of the 12AU7 are glowing?  If they are, do both your LED's light?

 

[benz]

Ok so what you are saying is i should do a resistance check for the grounds? they should all read zero right?

 

[benz]

Ok wait i am a little confused here so the resistance i am checking should read what?

 

[Grainger49]

Click on this link and perform the checks:

http://bottlehead.com/smf/index.php?topic=4812.0

Almost no meter will show 0 Ohms.  A properly zeroed analog meter will but digital meters always show the resistance of the meter leads.  This number is most often under one Ohm.  Since meter leads have resistance so will the wires in the ground path.  Any reading one Ohm and under is a good reading.

Report back any reading over an Ohm that you find.

 

[benz]

Ok just done my check from what i saw everything looks fine all are below one ohm.

 

[Grainger49]

Good!  That clears your ground path both from a safety aspect and potential hum producing problems.  It also helps where you got too much voltage on ground points.

Caucasian Blackplate (father of the Crack) asked if you are sure that both sides of the 12AU7 are glowing.  There are only a few things that will cause it to not conduct (turn on).

 

[Paul Birkeland]

You should consider re-reading my reply.

-PB

 

[Paul Birkeland]

This one?

"Are you 100% sure both halves of the 12AU7 are glowing?  If they are, do both your LEDs light?"

My message was to the original poster.  You could remove every ground wire from the Crack and the tubes would still glow.

-PB

 

[benz]

from what i see it looks like both tube are glowing

 

[Paul Birkeland]

If you got both halves of the 12AU7, then I would do another voltage checks.

In those places where you are supposed to have 0V, if you see a number on your meter, look for an indication as to whether those numbers are mV or V.  (I suspect they are mV)

-PB