Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Claudius on September 11, 2014, 12:28:40 PM
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(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
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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.
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Looks like you forgot the power supply wire from B2
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Looks like you forgot the power supply wire from B2
I sure did--thank you!
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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
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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?
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Do both halves of the 12AU7 glow?
Yes. The tops of the rods on both sides are glowing. Not very brightly, but evenly.
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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
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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.
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You can temporarily solder a wire between A3 and A8, just to see what happens.
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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.
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With the jumper in place, what are the voltages at T1/T5?
-PB
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With the jumper in place, what are the voltages at T1/T5?
-PB
T1- 123V AC
T5- 6.1V AC
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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
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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.
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Alright, you can actually listen to the amp like that.
The non-glowing LED probably got broken or melted in the build, and will need to be replaced. You can e-mail replacementparts(aht)bottlehead(doht)com
-PB
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Alright, you can actually listen to the amp like that.
The non-glowing LED probably got broken or melted in the build, and will need to be replaced. You can e-mail replacementparts(aht)bottlehead(doht)com
-PB
Paul-- Thanks for all your help! I'll request a replacement LED.
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I just plugged in my HD650s and the Crack sounds pretty good! Is it going to sound any different when I remove the jumper and replace the LED?
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Probably not. In hypothetical terms, a shared cathode connection can lead to crosstalk, but the dynamic impedance of that particular red led is so low that this isn't realistically a problem.
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Probably not. In hypothetical terms, a shared cathode connection can lead to crosstalk, but the dynamic impedance of that particular red led is so low that this isn't realistically a problem.
Thanks, that doesn't surprise me, given how good it sounds in it's current state.
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Hey guys
Thought I would comment here as I have a similar issue. I have manage to completely melt one of the LED lights. will it still work without this or should I just order a replacement ?
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Replacing it is best even if the voltages still read correct. If the voltages are not correct you must replace it for sure. You can order some replacements at [email protected].