My Crack build w/ manual queries

[Paul Birkeland]

They are. I'll double check the wiring in about an hour when I get home. What do the high voltages at T5, T9, A1,
B4, B6 suggest?

They are all related to the same problem, that one half of the 12AU7 isn't glowing.

If you believe it to be the LED, you can connect a wire between A3 and A8.

-PB

[denti alligator]

If you believe it to be the LED, you can connect a wire between A3 and A8.

I don't know anything ... I'm at your mercy

All I know is what I've posted. Is it possible the LED isn't working? is broken? What will wiring A3 to A8 do?

[denti alligator]

Wired A3 to A8. Same problem.

What should I try next?

[Paul Birkeland]

Wired A3 to A8. Same problem.

What should I try next?

I'm guessing one or both LED's light with the jumper in?

[denti alligator]

I'm guessing one or both LED's light with the jumper in?

Hadn't looked at the underside. Only half the tube glows (same half). Both LEDs light up now. Haven't re-checked voltages.

[denti alligator]

What should I try next? Should I remove the wire between A3 and A8 to start with, now that we've determined the LED is fine?

EDIT: Just double-checked all the wiring. Unless I'm overlooking something (possible, of course), I think everything is where it should be.

[denti alligator]

What are the chances the tube is no good?

[Doc B.]

Why don't you measure the resistance across each half of the heater?

[denti alligator]

Why don't you measure the resistance across each half of the heater?

Can you tell me how to do this.

[Paul Birkeland]

Set your meter to Ohms, put the black probe on pin 9 of the 12AU7 out of the socket, then measure resistance between 9 and 4, then 9 and 5.

-PB

[Jimb0]

I reflowed A5 and A6. Still not working. Any other ideas?

Judging by the picture it looks like you didn't put enough solder on some of those terminals but it could just be the way I'm seeing it from the picture. I don't think it would hurt to add extra solder.

[denti alligator]

Set your meter to Ohms, put the black probe on pin 9 of the 12AU7 out of the socket, then measure resistance between 9 and 4, then 9 and 5.

-PB

You mean the tube itself? pin 4 is 4.38k; pin 5 is 7.5

(Seems like pin 4 is fluctuating. Now I'm getting in the 600 range. Yeah, every time I try it I get a new number, ranging from 300 to 47k. Meter works fine, as far as I can tell, measuring other things.)

The solder on the terminals is about how much I've used on my past three successful BH builds.

[denti alligator]

Does this mean I have a bad tube?

[Doc B.]

Could be bad, but try cleaning pin 4 and measuring one more time.

[denti alligator]

Used deoxit. Still measuring all over the place.

EDIT: Guitar shop downtown has some Electro-Harmonix 12AU7s. Those any good? I might pick one up to hold me over till a replacement comes if it's really this tube that's bad.