Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: barnstead on April 05, 2022, 01:32:54 AM
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First time builder here. I'm having issues with the LED on A3 which is failing to light up. The other LED does light and the voltages (below) appear to be correct. Any guidance would be much apreciated.
1. 75
2. 174.8
3. 0
4. 174.8
5. 58.7
6. 0
7. 103
8. 0
9. 93.7
10. 0
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Do you have a picture of the 12au7 (9 pin) socket?
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Did you happen to build your Crack with the Speedball all at once?
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@Drew1d here's a picture of the 12AU7 socket.
@Paul No, I did buy the speedball but haven't touched it yet. It's just a standard Crack.
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Can you carefully measure the DC voltage at A3?
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I'm getting 0.03 volts through A3.
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Could you also post a photo of the octal socket wiring?
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Here it is, and one of the full amp.
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Can you check the DC resistance between A3 and terminal 3? Does it change without the 12AU7 plugged in?
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I get 6 ohms between A3 and terminal 3 with the 12AU7 in and out.
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Are A3 and A4 touching at all?
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No contact between A3 and A4.
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On the power transformer, remove the wires from terminals 7 and 9 and leave them poking up straight in the air then recheck the resistance between A3 and terminal 3.
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Still 6 ohms with the 12AU7 in and out and the wires out of transformer terminals 7 and 9.
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The most likely culprit here is that some debris has gotten into your socket and created a short between pins 3 and 4. You may just want to e-mail replacementparts(at)bottlehead(dot)com to ask about getting a new 9 pin socket and some fresh LEDs.
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Thanks Paul. I will do that. Appreciate the guidance.
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This is a simple vid on how I would check the diode and tube socket. (not tube, as I said in the video)
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Thanks Drew, I missed your video earlier, but unfortunately no diode setting on my multimeter.
I did get the new socket in and installed it. But now the A8 LED won't light. Voltage measurements still look good.
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And here's the picture of the rewired socket.
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What are your current voltages?
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1. 73.5
2. 173.2
3. 0
4.172.5
5. 81.5
6. 0
7. 101.7
8. 0
9. 107.0
10. 0
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Those are working voltages.
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I'm uncertain if you're still having the problem, the last thing you said was the other one isn't lighting, but the subject says the issue is resolved.
So, diodes are like one way streets right? And when electricity is running through it, it lights up. Now, I don't have a lot of experience with LEDs, but I would say that a bad diode would conduct electricity both ways.
If it was hooked up backwards for example, I wouldn't expect it to light up. (unless blown, though....I've never tried it.) I would expect that to be the most common error, although the picture looks right.
The other not lighting up problems would be from electricity not running through it, like,
- one side is not connected
- something internal to the piece is no longer connected
Assuming that the tube is fine, and it's the same one as before. They are "keyed" so you can only put that in one type of way. If you were using the same LEDs, and moved one to the other side when replacing the socket, then I would say there is probably some internal break in it.
Let's say that you got all new parts. I mean...it's possible that you got two bum parts, either the sockets or LEDs, but that seems unlikely.
I would take like a AA battery, and clip or tape a wire to each side of it. Now, with those two wires, touch the positive side (the nipple side) to the pin of the socket, and the negative side to the center of the socket, did it light up? Do the same to the other LED, does it light up?
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Paul, by current voltages do you mean the wall voltage? It's 120.4 volts. If not I may need a bit more guidance.
Not sure how this got marked resolved, it's still unresolved. Drew, can confirm both LEDs are functional, they were tested before I attached them to the new socket.
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The voltages you posted are correct and consistent with a working amplifier, I didn't notice that you said the A3 LED wasn't lighting up. What DC voltage do you see at A3 now?
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So right now it's the A8 LED that won't light. Before it was the A3 LED that didn't light (and A8 worked), I then installed the replacement socket and LEDs and now A3 does light up but A8 does not. Now I'm seeing 1.59 volts at A3 and 1.38 at A8.
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Reflow the joint at A5 and add a little extra solder.
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Reflowed and added solder to A5 but no luck.
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OK dude it can only be so many things. I think that you need to check the LED while it’s in the circuit not before. Try the battery test with the LED and see if it lights up. ( make sure the amp is unplugged and discharged ). If it lights up also check the LED with the tube plugged in. Perhaps when the pins wiggle when the tube is plugged in, it is breaking its connection. If that still lights up take the tube out and jam the wire into the socket and test. If that lights up replace the tube. Test the working side also to make sure your testing methods are sound. Is it possible that it is lighting up and the room is too bright? Does the amplifier work at all, or just one side? ( use crappy headphones to check, and not in your ears).
Not killing yourself, but you could test the voltage of the pins where each each led connects, while the amp is on. They should be similar and only a few volts. Being extremely careful, because the high voltage pins are next to it. Like, alligator clip before the amp is on, and turning the amp on/off by plugging it into the wall outlet. Black side to ground, red side to pin. I do the left hand in pocket, negative black side of the meter touching the metal chassis, and the red probe carefully touching the pin. Test one led then the other, same as above. But danger is my middle name, and I don’t recommend that to anyone not experienced.
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Reflow terminals 4 and 5, both upper and lower.
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Oh, I just read your post again. So if your getting the right voltages at the pin, then the amp should be working. Are you certain it isn’t? If it wasn’t connected you wouldn’t get any voltages there. Have you tried the amp?
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I reflowed 4 and 5 but no change. I haven't tried listening to the amplifier, going by what the instruction manual advises as far as not using it if the LEDs don't light up.
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The low voltage across the LEDs means not a lot of current is being drawn across it, but you have the correct current being dropped across the 22K resistor on that side of the amp. This could be caused by a flaky solder joint at A4/A5 making half the tube not heat up properly, or possibly a different loose solder joint in the amp, or even the lugs on the pot where the black wires connect may not be well soldered.
You're close to having a working amp, really you should just reflow all the solder joints in the amp other than the power switch and LEDs just to be certain they are all solid.
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Reflowed everything but A8 LED still not lighting up. All the solder joints look good to me.
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Can you post some fresh photos of your build as it sits now?
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Pics below
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I still see some questionable solder joints in the amp. The wiring around B7/B8 makes it look like one of the green wires is going to B6 instead, but that isn't the case is it?
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Right that's not the case re B7/8, though I did just take the chance to clean up that joint, which was a bit of a mess. No change with the LED though.
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Well, you could send this one in for repairs if you'd like. You would need to contact queen(at)bottlehead(dot)com to request this, being sure to mention that you've been working with me here.
There is very, very likely a flaky solder joint or two at work here.