Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Carolus on February 04, 2015, 09:47:28 AM
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Hello folks! :)
I finished my Bottlehead Crack yesterday and did a resistance check that looked OK. I therefore made the decision to try the amp with a pair of old headphones and skip the voltage check (stupid idea, I know). I guess all the warnings about life threatening voltage and current made me a bit unsure about fiddling around with live circuits. I double checked all circuits before powering on the amp, and thought that was enough. :-\
Anyhow, all seemed fine at first. The sound was nice and crisp, the channel balance was perfect and there were no strange sounds.
So today I decided to try the amp with my HD650, but after a couple of minutes I noticed a scratchy sound, kind of like white noise, that came and went multiple times. It disappeared for maybe a minute when I restarted the amp but then came back. I think it was mostly or only in the left channel. After some time I also lost almost all sound in the right channel.
That's when I did the voltage check. Here are the results:
1. 79
2. 184
3. 0
4. 184
5. 81-82
6. 0
7. 16
8. 0
9. 108 second time: 25
10. 0
11. 0
12. 0
13. 188
14. 0
15. 200
20. 0
21. 213-214
A1. 82
A2. 0
A3. 1-2
A4. 0
A5. 0
A6. 80
A7. 0
A8. 1-2
A9. 0
B1. 80
B2. 184
B3. 11
B4. 81
B5. 184
B6. 107
B7. 0
B8. 0
From what I can tell, 7 and 9 are way off.
When I checked the TSR-connections, the voltage rose to 46V. At least I think so. I don't know if I measured it correctly. I had to use the 20V option on my multimeter to get any readings and it showed 0.46. It then dropped to zero, but started rising to 0.05 multiple times. It did not seem to go allt the way down to zero and stay there.
What do you guys think is wrong with my amp, and how can I fix it? Do you think that my headphones took any damage from the amp during the short time (a few minutes) that I had them plugged in?
Thanks in advance!
//Carolus
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Are the 2.49K resistors on your headphone jack looking unusually burnt?
I think you have the wires going to the headphone jack feeding from the wrong terminals. With voltages like that, I would absolutely not listen to the amplifier until you've repaired the wiring error.
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Are the 2.49K resistors on your headphone jack looking unusually burnt?
I think you have the wires going to the headphone jack feeding from the wrong terminals. With voltages like that, I would absolutely not listen to the amplifier until you've repaired the wiring error.
They look completely normal. I did have to work a little to get them in the right position. Maybe that damaged them?
Are there any particular wires I should check?
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The next thing to check would be the solder joints on all the black wires.
-PB
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The next thing to check would be the solder joints on all the black wires.
-PB
Thanks for the tip! I have looked on all the joints several times, and all of them look fine. I can't see any joint that I would immediately suspect to not be ok. Almost all of them look nice and shiny.
Should I reheat them just to be sure?
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Yes, you can also tug a little on each black wire, one may just pop right out (which would indicate a bad joint).
-PB
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Yes, you can also tug a little on each black wire, one may just pop right out (which would indicate a bad joint).
-PB
All cables seem to be correctly fastened. I haven't reheated anything yet, but I just tested my multimeter on a 9V battery that shows up as 9.37V on the 20V setting, so I have apparently interpreted the readings the wrong way. The 0.46 is 0.46V, not 46 Volt. And 0.05 should be 0.05V.
So there doesn't seem to be any high voltage on the TSR. That's quite a relief. But that means that the voltage doesn't go up to 9V as it should.
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I tried the amp with my old headphones again, since there doesn't seem to be any high voltage to the TSR. Now another symptom showed up: low volume. I have to set the volume to max to actually hear anything properly. With all these different issues, my feeling is that some component is broken. The voltage reading on terminal 7 and 9 are really low, could that have something to do with it?
Should I reheat every joint anyway?
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I tried the amp with my old headphones again
Just for future reference, when your voltage are way off, you should not listen to the amp. There is no reason to (it will either not pass sound, or pass it with a lot of issues), and you could end up damaging whatever you plug into your amp. There won't be any additional information available from listening to the amp that isn't available from the voltage symptoms.
Now another symptom showed up: low volume.
As stated above, this is not an additional symptom.
Should I reheat every joint anyway?
Yes.
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Just for future reference, when your voltage are way off, you should not listen to the amp. There is no reason to (it will either not pass sound, or pass it with a lot of issues), and you could end up damaging whatever you plug into your amp. There won't be any additional information available from listening to the amp that isn't available from the voltage symptoms.As stated above, this is not an additional symptom.Yes.
Thanks for the information. I won't be plugging in any more headphones. The reheating did not correct the voltages, so I guess I'm going to have to send it in for the commercial repair service.
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Before doing that, I would post some photos of your build. We may be able to suss out what's going wrong.
-PB
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Before doing that, I would post some photos of your build. We may be able to suss out what's going wrong.
-PB
Here are some pics that I took:
https://imgur.com/a/XkniP/
Some of them are not great, so please tell me if I should take some more.
Edit: Attachments is in my next post.
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You need either post your pictures on the forum or make your pictures on imgur publicly viewable.
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You need either post your pictures on the forum or make your pictures on imgur publicly viewable.
The whole album should be public, but i'll have a look at it.
Fixed it:
https://imgur.com/a/XkniP/
Some of the wires on the transformer look badly soldered, but I have pulled on them and they are not coming loose.
Edit: I attached all pictures as well. I didn't think of that option. :)
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Thanks for posting up all the pics. Here's what I would do if I had the amp on our repair bench:
1. There's some bit of bare lead poking out around the headphone jack, I would look to make sure that wasn't loose, clip it off, and reflow that solder joint if necessary.
2. The wire from B3 to 7 looks suspicious. It looks like on the tube socket end, the bare wire just barely pokes through the tube socket terminal, and on terminal 7, it looks like the insulation may be in the terminal strip hole a little bit. If you wiggle that wire, does it move on either end of its connection? I would probably just remove that piece of wire and replace it with one slightly longer, then take half a wrap on each end to secure it. The B3 end may OK, it's just tough to tell if the bare wire is bent up against the socket terminal (which is a good thing if it is)
I'd start with those two and see if things change. By the way, you have some of the nicest looking twisted wire that I have seen in a long time!
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Thanks for taking the time to look at my soldering, and for the compliments on my twisted wire. :)
I just trimmed the bare wire at the headphone jack. I don't think it should have anything to do with the voltage problem since the joint itself looks solid.
The wire on B3 just barely pokes trough about a mm upwards, but as far as I can tell it is soldered on with a good amount of shiny lead that fills up the hole. It also feels completely fastened and I reheated it earlier as well.
The insulation on the wire going in to 7 is right up against the terminal, but I don't think it's in the actual hole. It feels stiff and completely soldered on when I wiggle it and the end is wrapped around the terminal itself. There is no free play in the wire.
I will try your recommendations before I send in the amp. The capacitor on 9 and 10 feels loose when I wiggle it, but I know it is soldered on, so it has to be something with the capacitor. The capacitor closest to the RCA connectors made a loud bang when I reheated it, but it seems to be working just fine and giving correct Voltage readings on terminal 21. Maybe I should replace it anyway since I've heard that capacitors that get short-circuited tend to have a reduced lifespan.
I'll update you on my progress later, but if I can't fix it over the weekend, then I probably will send it in. How is the repair backlog at the repair department?
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Maybe I should replace it anyway since I've heard that capacitors that get short-circuited tend to have a reduced lifespan.
I have yet to have one of those capacitors present a problem in any repair or any build online, unless they are really horribly burned by a soldering iron.
I'll update you on my progress later, but if I can't fix it over the weekend, then I probably will send it in. How is the repair backlog at the repair department?
I plan to clear the bench today, but there are several sets of packaging floating around out there that haven't been shipped back yet.
-PB
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I changed the wire going from B3 to 7 and made sure that the wire was bent up against the terminal like a hook, but I still get the same wrong voltage readings on terminal 7 and 9.
Is there anything else I could try? Maybe I have to change some components? I feel like just sending it in to Bottlehead, but the shipping both ways would probably cost about as much as the actual repair service.
Edit: Added some pics. The focusing on my phone camera is not so good, but the wire is protruding through the terminal hole in both joints.
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Does your 6080 glow with the amplifier on?
It is very rare, but I have seen a case or two where the red/black twisted pair going to B7/B8 was able to heat the 12AU7, but not the 6080, due to bad solder joints on the octal socket.
-PB
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Yes, the 6080 glows.