Volume imbalance and high voltage in one channel

[antjuneau]

On my Crack + Speedball I'm getting a weird issue. The left headphone channel is louder than the right and all voltages are correct except terminals 1 & 7. I'm getting 160 volts at terminal 1 and 166 volts at terminal 7. Any ideas on what my issue is? Could it be one of the tubes?

[Paul Birkeland]

First things first - you failed the voltage checks and shouldn't be using the amplifier.

Now that I've gotten that out of the way, do both LED's glow on the 9 pin socket?

[antjuneau]

Yes, all LEDs are glowing.

[Paul Birkeland]

You almost certainly have switched a pair of R1 resistors between the big board and the small board.

[antjuneau]

You were right, I had switched one of the resistors accidentally.

However I just switched them to their correct positions and I am still getting high voltage on those same two terminals. All LEDs are still glowing, although the two LEDs on the top of the big board fire up quicker than the two LEDs on the bottom of the big board.

[Paul Birkeland]

What are your actual voltages (just on terminals 1, 2, 4, 5, 7, and 9).

-PB

[antjuneau]

1 - 157
2 - 179
4 - 179
5 - 81
7 - 160
9 - 121

[Paul Birkeland]

Can you pull the 6080 and remeasure terminals 1 and 5 with just the 12AU7 in the amplifier?

[antjuneau]

1 - 173
5 - 80

Also, now only half the LEDs on the big board are glowing.

[Paul Birkeland]

If you have 173V on terminal 1, you either still have a 31.6 Ohm resistor on the small PC board, or you have a miswire.  The "I" pad on the little PC board needs to go to terminal 2, and the "O" pad goes to terminal 1. 

Since both LED's on the 9 pin socket are glowing, we know that the tube is conducting.  The high voltage at terminal 1 indicates too much current is being drawn.

I would imagine that if you look at the LED's on the 9 pin socket, one is glowing much more brightly than the other. 

Just out of curiosity, did you install the Speedball into a working stock Crack?

[antjuneau]

I'm not getting any continuity across the 31.6 ohm resistor that I switched out. I need to order one. I'll report back when I install it.

[antjuneau]

And to answer your question, I built the crack first without the speedball and it was fully functional.

[Paul Birkeland]

The 31.6 Ohm resistor is not of concern here, and is not relevant to the tests I'm having you do, nor to the voltage at terminal 1.

[antjuneau]

The 31.6 Ohm resistor is not of concern here, and is not relevant to the tests I'm having you do, nor to the voltage at terminal 1.

Ok I understand that it may not be causing the issue here, but all R1 resistors are in their proper place now and one of them is broken and needs to be replaced either way.

To answer the LED question, yes, the A8 LED is considerably brighter than the A3 LED. What's the next step? Need me to check any voltages or resistances anywhere else?

[Paul Birkeland]

To answer the LED question, yes, the A8 LED is considerably brighter than the A3 LED. What's the next step? Need me to check any voltages or resistances anywhere else?

I believe you still have a 31.6 Ohm resistor on the PC board feeding terminal 1. 

If the resistors are in their proper places, then you may have both red wires going to that board sitting in the "O" pads, though the LED's on the board shouldn't glow in that case.