Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: antjuneau on December 19, 2015, 03:48:30 PM
-
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?
-
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?
-
Yes, all LEDs are glowing.
-
You almost certainly have switched a pair of R1 resistors between the big board and the small board.
-
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.
-
What are your actual voltages (just on terminals 1, 2, 4, 5, 7, and 9).
-PB
-
1 - 157
2 - 179
4 - 179
5 - 81
7 - 160
9 - 121
-
Can you pull the 6080 and remeasure terminals 1 and 5 with just the 12AU7 in the amplifier?
-
1 - 173
5 - 80
Also, now only half the LEDs on the big board are glowing.
-
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?
-
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.
-
And to answer your question, I built the crack first without the speedball and it was fully functional.
-
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.
-
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?
-
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.
-
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.
-
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.
I've triple checked resistances across all four R1 resistors - they're definitely in the right place.
All wires going to and from terminals 1-5 have been double checked and re-soldered. Same thing for the 9-pin socket.
Any other ideas? I'm about ready to just order 2 more small boards with parts and solder them in :-\ I've been trying to figure this one out for 2 weeks now.
-
I went a re-soldered a bunch more connections and now I'm getting a different issue. Instead of high voltage on terminals 1 & 7, I'm getting low voltage on terminals 2, 4, 7, and 9.
2 - 95
4 - 95
7 - 71
9 - 83
And now only one LED isn't glowing - one of the LEDs closest to the edge of the big board, specifically the side of the board connected to 3U & 9L.
When I unplug the power tube and leave in the 12AU7 I get high voltages at 1,2, & 4:
1 - 182
2 - 205
4 - 205
Terminal 5 is correct at 79 volts.
Hope this combination of clues helps. I've checked and re-soldered just about everything south of the tranny.
-
Voltages now:
1 - 60
2 - 94
3 - 0
4 - 94
5 - 86
6 - 0
7 - 59
8 - 0
9 - 85
10 - 0
11 - 0
12 - 0
13 - 94
14 - 0
15 - 140
16 - 0
17 - 0
18 - 70
19 - 68
20 - 0
21 - 186
22 - 0
Low voltages everywhere. Can anybody help? Blackplate?
-
I think I found it. I'm getting 0 resistance between the outer legs of one of the MJE350 transistors. Going to order one and report back if it fixes the issue.
-
Please pull the 6080 and recheck the voltages on 1-5.
To reiterate, you must get 60-90 volts on terminals 1 and 5 and roughly 200V on 2 and 4 before going back to run the 6080. Until you can pass this check, please do not run the amp with the 6080.
-PB
-
Please pull the 6080 and recheck the voltages on 1-5.
To reiterate, you must get 60-90 volts on terminals 1 and 5 and roughly 200V on 2 and 4 before going back to run the 6080. Until you can pass this check, please do not run the amp with the 6080.
-PB
Is this true even with the bad MJE350? I'm getting:
1 - 80
2 - 198
4 - 198
5 - 173
-
So when we first did this test, terminal 5 gave you the voltage you were looking for and terminal 5 did not. Now, terminal 1 is correct and terminal 5 is not.
Completely ignoring the 6080 and the big PC board, what else has changed in the amplifier that could have precipitated this change?