Crack voltage issues / LEDs not lit

[Claudius]

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FqH3aqeI.jpg&hash=08f2ab1a468242b3fc92b0dae5b88502a35acbb3)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FmF3hWtQ.jpg&hash=957381dca239bab1b7a461c301ae3def0bc09c4b)

I just finished my Crack and although the resistance check was fine, the voltage check came up with some problems, and the LEDs aren't lighting. I checked and tube heaters are getting the correct AC voltage, so I wonder if it's a problem with the input tube. The power tube lights up like a Christmas tree, but the input tube only has two tiny spots that glow.

Location: Voltage

1- 0
2- 0
3- 0
4-0
5-0

6- 0
7- 71
8- 0
9- 70
10- 0

11- 0
12- 0
13- 201
14- 0
15- 213
20- 0
21- 226

A1- 0
A2- 0
A4- 0
A5- 0
A6- 0
A7- 0
A9- 0 (multimeter clicks continually)

B1- 0
B2- 200
B3- 70
B4- 0
B5- 200
B6- 70V
B7-  0 (multimeter clicks continually)
B8- 0

[tjessen]

As far as the tubes lighting up, your description seems normal. I know everyone will seem to tell you this but check your connections in the amplifier circuit.

[mcandmar]

Looks like you forgot the power supply wire from B2

[Claudius]

Looks like you forgot the power supply wire from B2

I sure did--thank you!

[Claudius]

I'm getting closer--but no cigar...yet. One LED is lit, but the one attached to A8 doesn't look like it lights.

Location: Voltage

1- 152
2- 170
3- 0
4-170
5-76

6- 0
7- 152
8- 0
9- 102
10- 0

11- 0
12- 0
13- 170
14- 0
15- 194
20- 0
21- 218

A1- 75
A2- 0
A4- 0
A5- 0
A6- 153
A7- 0
A9- 0 (multimeter clicks continually)

B1- 152
B2- 169
B3- 152
B4- 75
B5- 170
B6- 102
B7-  0
B8- 0

[Paul Birkeland]

I'm getting closer--but no cigar...yet. One LED is lit, but the one attached to A8 doesn't look like it lights.

Do both halves of the 12AU7 glow?

[Claudius]

Do both halves of the 12AU7 glow?

Yes.  The tops of the rods on both sides are glowing.  Not very brightly, but evenly.

[Paul Birkeland]

Try poking at the LED that isn't glowing with a wood chopstick (or stick from the yard, but not a wet one!) while the amp is running.  You may have a loose connection that isn't allowing the 12AU7 to draw any current.  Also gently poke each 22K resistor to see if the LED pops on. 

-PB

[Claudius]

Try poking at the LED that isn't glowing with a wood chopstick (or stick from the yard, but not a wet one!) while the amp is running.  You may have a loose connection that isn't allowing the 12AU7 to draw any current.  Also gently poke each 22K resistor to see if the LED pops on. 

-PB

I tried some gentle prodding with a chopstick on both the LED and 22K resistors--no change. I also reflowed the joints on both sides of the LED--no change.

[Paul Birkeland]

You can temporarily solder a wire between A3 and A8, just to see what happens. 

[Claudius]

You can temporarily solder a wire between A3 and A8, just to see what happens.

Ok, I jumpered A3 to A8 and checked the continuity to make sure the connection was good, but the A8 LED still isn't lighting.

[Paul Birkeland]

With the jumper in place, what are the voltages at T1/T5?

-PB

[Claudius]

With the jumper in place, what are the voltages at T1/T5?

-PB

T1- 123V AC
T5- 6.1V AC

[Paul Birkeland]

Sorry, I should be more specific, what are the DC voltages at terminals 1 and 5 (outside lugs on the 5 lug strip at the 9 pin socket).

-PB

[Claudius]

Sorry, I should be more specific, what are the DC voltages at terminals 1 and 5 (outside lugs on the 5 lug strip at the 9 pin socket).

-PB

Ok, gotcha.  78V at both 1 and 5.