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May 31, 2020, 06:17:52 AM

Author Topic: One headphone doesn't work  (Read 169 times)

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Offline cayoung05

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One headphone doesn't work
« on: May 23, 2020, 02:24:22 PM »
Hi all,

I built my Crack awhile ago and recently my left headphone ear stopped working and I could hear a slight popping/humming sound in both. Today I reflowed all the joints and the humming sound is gone and the right ear sounds great, but the left ear still doesn't work when the headphone jack is pushed all the way in. If I push the headphone jack 1/4 to about 3/4 of the way down, I can hear through both ears. It's only when the headphone jack is pushed all the way down that the left ear stops working. I did a little research and from this thread (https://forum.bottlehead.com/index.php?topic=4851.0) it looks like I may need a replacement jack? Thanks in advance for your help,

Chris

Offline Paul Birkeland

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Re: One headphone doesn't work
« Reply #1 on: May 23, 2020, 03:31:30 PM »
See Crack FAQ item #12:
https://forum.bottlehead.com/index.php?topic=4295.0

How are your DC voltages?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cayoung05

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Re: One headphone doesn't work
« Reply #2 on: May 24, 2020, 09:33:41 AM »
Hi Paul, thanks for the help. Here's my DC voltages based on the Bottlehead Crack checklist in the manual:

Terminal - Voltage

1 - 147.8
2 - 164.4
3 - 0
4 - 164
5 - 148.6
6 - 0
7 - 147.3
8 - 0
9 - 147.1
10 - 0
11 - 0
12 - 0
13 - 163.6
14 - 0
15 - 190
20 - 0
21 - 215

A1 - 148.2
A2 - 0
A4 - 0
A5 - 0
A6 - 147.4
A7 - 0
A9 - 0

B1 - 147.4
B2 - 163.6
B3 - 147.2
B4 - 148.5
B5 - 164
B6 - 147.5
B7 - 0
B8 -  0

It looks like all the voltages that are supposed to be 90 (based on the manual voltages) are around 148. Is this something to be concerned about?

Offline cayoung05

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Re: One headphone doesn't work
« Reply #3 on: May 24, 2020, 09:37:50 AM »
I also tested the tip of the headphone jack, and the voltage climbed to around 10 volts then dropped to 0

Offline Paul Birkeland

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Re: One headphone doesn't work
« Reply #4 on: May 24, 2020, 03:40:48 PM »
Does your 12AU7 glow?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cayoung05

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Re: One headphone doesn't work
« Reply #5 on: May 24, 2020, 03:45:31 PM »
Yep, I can see light in both tubes. Here's a pic for reference

Offline Paul Birkeland

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Re: One headphone doesn't work
« Reply #6 on: May 25, 2020, 05:22:59 AM »
Can you post some build shots of the inside?

Neither half of your 12AU7 is conducting, so you definitely don't want to listen to this amp just yet.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline cayoung05

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Re: One headphone doesn't work
« Reply #7 on: May 25, 2020, 09:01:17 AM »
Hi Paul,

Here's some pics of the inside. I apologize for how messy the solders and the inside might look, it was the first solder job I did back in high school (which tells you how great and clear the manual was for learning/building an amp!). Let me know if you need additional pictures to clarify anything. Thanks again for your help,

Offline Paul Birkeland

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Re: One headphone doesn't work
« Reply #8 on: May 25, 2020, 10:51:11 AM »
It looks like pins 4 and 5 on the 9 pin socket have been forced together, then soldered into one lump.

From what I can see, I would remove the 9 pin socket, cut out all the wiring that goes to/from that socket, and rewire it. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deluk

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Re: One headphone doesn't work
« Reply #9 on: May 26, 2020, 07:37:47 AM »
The short wire from the resistor should go to A6 and not A5? Wire going to A5 then bridges across to A4.