Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: danosol on May 31, 2013, 07:00:48 PM
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Just went to Bottlehead today and got a new B board and the fixings and it was working fine when I left. I get it home and it works for about two songs and then I hear this static noise and swooshing. So I lower the volume all the way and power down and the headphones get a loud pop. The first time it did this the LED's on the B board stopped working. I heated all the connections with the iron and thought i had it fixed the second time but the same static and swooshing. This time when I turned it off I still got the pop but LED's are still on.
Help!
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Triple check those 2.49K resistors on the headphone jack, just to be safe.
You could get popping and swooshing from something heating up and misbehaving, did any of this occur before installing the Speedball? Knowing that Doc B. built the board (with a fresh tip in the iron I noticed), I might suspect a 12AU7 being a little fussy. I'd recommend leaving the Crack on overnight with no headphones plugged in to let the tube cook a bit, that may end up remedying the problem on its own.
-PB
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No it sounded great and no issues pre speedball, but I didn't have it that way for long. I have no problem leaving it o over night but if the LED's go out on the B board and the amp is on all night will that be a problem?
Could a bad 12AU7 cause those issues?
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Went back and checked the 2.4k resistors and noticed the LED's on the B board went out. I powered down and reheated the two 2.4K resistors and when I powered the Crack back on the LED's were back on.
Went back and checked the LED's again and they were out on the B board again. Powered it up a minute later and they went on again. I think you are right. Something is heating up and causing the LED's to go out. But what?
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Anyone out there?
Fired it up this morning and lights went on and out a few moments later. I tried 2 other 12AU7 tubes and nothing different.
Help!
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What are the voltages at 1 and 5 when the lights go out?
-PB
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87.3 at 1 & 163 at 5
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Ok, on the side with 165V, what is the voltage at "I" on the small PC board?
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170
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OK, this narrows the potential issues down to:
1. LED connection/functionality (shouldn't be a problem since the amp was working pre-Speedball).
2. A poor connection from the wire leaving the center lug of the volume control to that particular channel (worth double checking).
3. Issues within the C4S itself. I would quadruple check the ground connection to the board.
4. Issues with the wire leaving the "O" pad on the PCB, and heading to the 12AU7 (same as #2, just give it a good look over).
You can always do the chopstick test, find a wood or all plastic poking implement, then poke each transistor, LED, resistor, and wire leaving the offending PC board while the amp is running and the LED's are out. At some point, you will poke the right part and it will reveal itself as the problem.
-PB
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Well I heated up the first LED again and pushed it a bit away from the board and they both lit up. Gonna leave it on for a bit and see what happens and I'll report back.
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2 plus hours of listening later and no dropouts. Crossing fingers but I think getting the LED a bit off the board helped. In the process of doing this I decided to rewire transformer terminal 4 to 22 and then move it back to terminal 14U. In the process I accidentally burned a wire on the power socket (No Prob) when I went to put a new wire there it wouldn't take solder and I ended up melting the tab in to the socket a bit. It all works, but would you guys sent me a new power socket. I would sure appreciate it.
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dan...
Hang in there. Those LEDs are physically delicate but I soldered and resondered my old C4S board LEDs almost a dozen times, seriously. I ended up putting in current HLPM 6000 LEDs which were swapped a number of times themselves. My problem was I had the input and output wires swapped.
Just be patient.
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I wish I could have done that with the previous board. I could have avoided a lot of headaches.
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Well after a day of not using the Crack I fired it up and the LED's went out again >:(. This is getting old fast. Super disappointing. I just want to listen to some music!
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It is probably worth rolling in a different 12AU7 if you have one.
You should also have a look at the 12AU7 itself, to see if one half of it goes dim when you're having your issue (half of the heater could be getting crusty once it's warmed up).
-PB
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Just reheated the LED again and It's working, but for how long. If you're looking from the back it seems to be the LED on the left cause when they are out the one the right is lit but very very dimly.
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Ajay, if you could leave it with us for a day I'm sure we can carve out some bench time to go over it more rigorously and sort it out for you. Maybe the 2N2907 or an LED was stressed when the MJE350 was in backwards and is having some kind of intermittent issue or something. If that is the issue we can build up a new board and install it for you.
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I'll see how this goes. It's a bit expensive taking the ferry over. You guys have been very generous however, and I appreciate that. I think it may be the LED's but why would it work for a full day and all of a sudden stop. I don't think it's the 12AU7 I tried another 12AU7 prior to this and it made no difference. I also metered the transistors and they all tested OK. I'm currently about a half an hour into the re-flow of solder on the LED that I think is the culprit so I'll be a bit more patient.
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My hunch is that it may be a thermal issue. It might be that when the amp goes through a warm up and cool down cycle that a solder joint that looks good shifts ever so slightly and a connection is opened. Reflowing the joints on the C4S is indeed a good place to attack the problem. Luckily the components on the board are all pretty heat proof so you don't need to worry about reflowing the pads if necessary.
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I agree with Doc, I have yet to see an LED that sometimes works, either they conduct and function, or they are 100% broken (generally from being overheated).
If you had an MJE-350 in backwards, then the 2N2907 is probably also toasted.
What part of town are you in? I'd be happy to host you over the weekend and look over your amp (I'm in SE King County).
-PB
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Fired it up this morning and It seems to be working. I didn't flip it over to check to see if the LED's were lit up, but I asume it was.
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PB that would be awesome! I live in North Edmonds. Let me know what works for you and I'll be there. I will in the interim keep tabs on it during the rest of the week and see what happens.
I do notice that it gets pretty hot, both the chassis plate and the transformer after about an hour plus. If I try and grab the transformer by it's sides I can't hold it for long cause it's so hot. I'm s that's normal but not sure.
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Yes, it will get pretty hot. That's normal.
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Seems to have stabilized. I put in 5 hours last night with the amp being on and i fired it up this morning and no problems. Been running it a bit the last few days.
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Got home from work today, put in my Bendix 6080 and after a few minutes the right channel went out and practically took out my right eardrum. LED's out again on board B. This is rediculous. I am done flowing solder! It should either work or not. There has to be more robust components to use.
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I will suggest one more time that you let us do the repair for you.
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How do I measure the components to find the problem? Im sure it's the LED's. where can I buy a surplus of them. What is the point of diy if you do it for me.
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Im sure it's the LED's.
I'm 99% sure that your issue is not the LED's.
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PB when are you able to look at the amp with me?
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I'll be up at B-HQ tomorrow, but I can make myself available on Friday or Saturday if you'd like to stop by.
-PB
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That would be great, PM me your address and time for Friday. Also can you grab any parts you think may be required.
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Yup it's the LED. touched it with a chopstick and it lit up and vice versa.
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I know you're not going to like this, but that leads me to believe the problem is one of the solder joints around the LED, not the LED itself...
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Adam is correct, that would nearly always be a funky solder joint.
-PB
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Too late I already yanked that LED and tried to replace it with another that I pulled off from the previous board and it wouldn't light up at all. Paul make sure you grab some LED's to bring to your place for tomorrow.
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Paul make sure you grab some LED's to bring to your place for tomorrow.
I assume you meant to write: "Paul, I would be grateful if you could please bring some LEDs to your place tomorrow."
;)
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Yes, and appreciative. ;D
I'm usually not that rude. Many other things going right now that have caused my gratitude to go out the door. My apologies Paul and Doc if I have come across rude or unappreciative.
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Paul has already built a completely new board for the repair.