Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Jimmye00 on September 02, 2020, 08:34:28 AM
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So i completed my speedball insert and i have a loud hum coming from both channels. I went back and looked over both manuals. I started by completing the basic build and it worked great for a year. However after the upgrade i have the hum. I noticed a few things my build looked identical to the picture at the end of the basic build. However, at the beginning of speedball manual page 15 the picture has different wiring on the power unit, different wiring and different color wiring. but there are no directions that state i need to rewire these things. was wrong to assume that a prewired stock crack was ready to just proceed with the new components or do i need to rewire these things? All of my measurements for the speed ball were with in the state spec of the speedball manual. i have also attached a pic of my build. I appreciate the help!
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There are two versions of the Crack, basically an old and a new, so no rewiring is necessary.
What are your voltages on terminals 1-10?
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1. 85
2. 178
3. 0
4. 178.6
5. 78.7
6. 0
7. 111
8. 0
9. 109
10. 0
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Is the hum there regardless of the position of the volume control? Is it 60Hz or 120Hz? (you can listen online to a 60Hz and 120H tone to compare against)
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its more like a 120 hz buzz and its quite loud. volume knob does nothing to reduce or increase
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That would be expected if one of the 220uF power supply caps came loose.
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None of the brown caps on the PSU seemed loose but I reflowed the soldier just Incase. This did not fix the problem
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Is 16L soldered?
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Yes this goes
To the ground screw I believe?
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Yes, it looked in the photos like maybe it wasn't well soldered. Are there any other symptoms going on with the amp? If that connection was bad, you might get a little tingle touching the chassis for instance.
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Everything was perfect for a year prior to installing the speedball. So that makes me think it has to be something I did wrong in that area. When I was unplugging my headphones and touching the volume knob which is metal I could feel a bit of tingling electricity. I appreciate your help!
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Everything was perfect for a year prior to installing the speedball. So that makes me think it has to be something I did wrong in that area.
This is frequently not the case. More often than not, the process of installing a Speedball may disturb connections that weren't 100% in the original build, then people will spend all their time debugging what is likely a working Speedball and not looking for what's actually gone wrong.
If you got a tingle from touching the amp, the chassis plate isn't well grounded, and that terminal I brought up looked poorly soldered.