Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: denti alligator on April 06, 2017, 08:43:40 AM
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My Crack has started to act funny. With Speedball.
After about 5 minutes of playing the left channel goes out. The LEDs on the Speedball go dead, too. If I let it sit an hour or so and flip it back on I get another 5 minutes before it goes out.
I'll resolder around the Speedball and see if that helps, but thought I'd probe the forum for any obvious fixes.
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So I reflowed a bunch of joints, including everything on the main speedball board. Still, after 5 minutes the left channel goes out. The LEDs on the big board go out.
What would be causing this? How could I be getting great sound out of both channels, but only for 5 minutes. Each time! It must have something to do with the heat that's being generated...
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Tested voltages, which are all on.
Tried it again. 4:52 minutes and the left channel goes out with a pop.
I'm giving up for now.
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I had this "pop" on my non Speedball crack and it tuned out to be a poor connection on one of the leds on the small valve. Dab of new solder fixed it. As mentioned if they are fitted too tight they can break a lead if the valve is moved or replaced. Worth a look. Might need to gently lever on the connections.
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I had this "pop" on my non Speedball crack and it tuned out to be a poor connection on one of the leds on the small valve. Dab of new solder fixed it. As mentioned if they are fitted too tight they can break a lead if the valve is moved or replaced. Worth a look. Might need to gently lever on the connections.
Thanks, I just tried this. There seemed to be no issues, but I reflowed the joints anyway. Unfortunately, I'm having the same issue. 5 minutes of stereo audio, then a pop, then only the right channel.
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Have you tried a different 12AU7(the small tube)? It has two sides.
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Have you tried a different 12AU7(the small tube)? It has two sides.
Yes, I have. I'll try yet another one.
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As always it is helpful to see voltages and photos of the installation in order to offer some suggestions.
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The voltages were on, but I'll re-test and post them with photos after this next try (just re-soldered one of the wires going to the large pc board that might have been loose).
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something seems to be wrong with terminal 9. It's measuring 1.472
Maybe the cap has been damaged? (I only have a matching replacement pair of 100v 250uF caps, which won't work here, or?)
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If the cap was drawing down the voltage, it would explode and blow its guts out all over your amp. Since it hasn't done that, it's not the problem.
Are your 270 Ohm power supply resistors starting to discolor a lot? Improper installation of the TIP50 transistors onto the heatsinks can cause a low voltage like that, but you'll have low voltages everywhere else in the Crack.
How are the solder joints on the TIP50 feeding terminal 9? You might want to reheat those joints.
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No discoloration.
Just a note: I had this amp up a running for a long time (over a year) without problems or significant changes. But I moved, so something might have been bumped loose? I'll reheat the joints at 9 and leading to it.
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I reheated the joints leading to 9, including the TIP50 connections.
Again, it's fine for almost exactly 5 minutes. The voltage at 9 reads right. Then, suddenly, the LEDs behind the TIP50 go out and the voltage drops (and the sound goes out in the left channel).
Any idea what could be causing this? I find it especially odd that I get 5 minutes worth of power every time.
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Tried reheating some other joints. 5 minutes later, the LEDs are out again. Here are the post-5 minute voltages:
1 76.2
2 199.4
3 0
4 199.6
5 76.5
6 0
7 90.1
9 1.465
10 0
12 0
13 199.6
14 0
15 212
19 92.9
20 0
21 225
A1 76.6
A2 0
A3 1.564
A4 0
A5 0
A6 76.5
A7 0
A8 1.565
A9 0
B1 76
B2 199
B3 90.1
B4 76.8
B5 199.1
B6 1.457
B7 0
B8 0
Reheated A3, A8 and B6. Same problem. What's with the 5 minute delay?
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Have you tried reflowing the LED joints on the pcb board ofside thats not working? I had something along the same lines happen with my Eros and it took a while to track down, after a fair bit of prodding with a wooden chopstick while the amp was running the problem turned out to be the solder joint on one of the LED leads. After about 10mins I am guessing the joint would heat up enough and expand enough to break the contact. The amp had run fine for many months prior and the issue only came after moving the amp to a new location.
Its a easy enough thing to check
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Thanks, I have tried that. But I will try it again.
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Hey Sam, I had a similar problem in my Eros (lost a channel after 4-6 minutes, and this was also after having decent operation for months before the problem exhibited itself.)
You may have already re-soldered these, but for me, it was a 2N2907A--one of the solder joints on the legs wasn't solid. I don't use a lot of solder on those little joints, and I guess it wasn't enough.
I ran across this when I was trying to figure out if it could have been the 2N2907A:
https://www.head-fi.org/t/476650/crack-bottlehead-otl/8115#post_13288157 (https://www.head-fi.org/t/476650/crack-bottlehead-otl/8115#post_13288157)
Possibly worth a shot if you haven't already tried it. Good luck.
Mary
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It probably wouldn't hurt to try a different 6080 as well, but your voltage measurements have me suspicious that replacing the 2N2222 and TIP50 on the offending side might be in order.
DO NOT reheat the solder joints on the LED's. The HLMP-6000 is hygroscopic and after such a long time out in the open, reheating the LED's with a soldering iron may cause them to crack.
-PB
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I have swopped out the 6080 and it makes no difference. Are there any joints you suggest I re-try before we try replacing parts?
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I have swopped out the 6080 and it makes no difference. Are there any joints you suggest I re-try before we try replacing parts?
Both of the transistors on the big C4S board that feed that offending side. Also check for loose or broken wires.
-PB
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Done... and for the first time ever I have smoke !!
Turned it off instantly. What to do now?
(Looks like the wire connecting 14 to 20 was melting... if that tells you anything)
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Measure the resistance between the "O" pad on each side of the big C4S board and ground. We are getting somewhere I think.
-PB
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I'm not getting a reading at all on either side.
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Redo the voltage test with the 6080 removed.
-PB
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1 -0.23
5 -.156
7 -.091
9 1.392 (and steadily decreasing)
15 244.5
18 96.9
19 96.9
21 245.1
A1 -.187
A3 .859
A6 -.079
A8 .909
B1 -.034
B3 .087
B4 -.113
B6 1.281 and steadily decreasing
all the rest are 0
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What do you have at terminal 2? (Your 12AU7 is still plugged in, right?
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12AU7 is still in.
Terminal 2 is getting no reading. The +/- is flickering and it shows 0.
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How about terminal 13? How about B2 and B5?
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I could check them again, but everything I didn't list was 0 or no reading.
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B5 and 13 are 0
B2 is 0.002
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T13 and T15 connect together with a 270 Ohm resistor. To get full voltage at 15 and no voltage at 13 indicates that either the 270 Ohm resistor between them isn't well connected, or you have a short somewhere down the line of terminal 13 that is pulling all the B+ down across said 270 Ohm resistor. Based on your relatively high available voltage, I can determine that the resistor between 13 and 15 is either open or poorly connected
-PB
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Yeah, that resistor is looking discolored. Wiring going to the power switch from the transformer (under the resistor) and from 20 to 14 (as well as part of the wire going from 12 to 14) are looking partly singed/melted. This is clearly where the smoke was coming from.
What to do? Can I request extra parts from you? I don't understand how this area got hit when I was trying to solve an issue on the PC boards.
Can use 250ohm or 300ohm 5W resistors? Parts Express only has those, not 270ohm.
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250 Ohms is OK.
Generally this resistor cooks when there is a short wired into the amp. The most common cause of this is when the TIP50 transistors aren't properly insulated from the heatsinks (the mounting kits aren't installed properly, almost always the shoulder washer is upside down or not seated well). Once or twice we have seen people replace the 270K/1W resistor with a 270/1W resistor, and that will also cause similar issues.
-PB
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Do you suggest replacing the transistor, too? Wasn't that the source of the problem to begin with--probably?
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Do you suggest replacing the transistor, too? Wasn't that the source of the problem to begin with--probably?
I've never seen a failed transistor cause that issue.
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I'm going back to the original problem of the channel going out after 5 minutes. If I fix this problem at terminals 13-15 I'm back to where I started with the PC boards...
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Also, remember that the amp worked fine for over a year. Unlikely the transistors aren't well insulated, or else they would have failed sooner. Or not?
I'm afraid of replacing the wirewound resistors and then getting them fried again. How do I prevent that?
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I'm going back to the original problem of the channel going out after 5 minutes. If I fix this problem at terminals 13-15 I'm back to where I started with the PC boards...
Your problem is that the high voltage isn't making it to the tubes. You can focus on the issue of the amp going out after 5 minutes, but your voltage measurements indicate that the amp isn't working at all.
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Also, remember that the amp worked fine for over a year. Unlikely the transistors aren't well insulated, or else they would have failed sooner. Or not?
I'm afraid of replacing the wirewound resistors and then getting them fried again. How do I prevent that?
I've seen the insulation issue come up both randomly and at the time of construction. Do keep in mind that one of the primary reasons that we came out with Speedball 1.1 was because so many builders were improperly mounting the TIP50's.
Replace the 270 Ohm resistor, then run the amp without the 6080. Use a pair of clip leads to have your meter reading the voltage at terminal 2 while you turn the amp on. If this voltage drops below 130V, then turn the amp off and report back.
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OK, thanks.
Any chance these resistors could work? I can't tell the wattage.
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Look like Kiwami 2 watt.
Cheers,
Geary
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OK, thanks.
Any chance these resistors could work? I can't tell the wattage.
What are you going to use those for? They don't seem related to repairing your Speedball.
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I was hoping I could use them in place of the wirewound resistors, but obviously they aren't the right wattage.
I've ordered replacement parts. Should be here tomorrow.
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I was hoping I could use them in place of the wirewound resistors, but obviously they aren't the right wattage.
They aren't exactly the right value either.
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Replace the 270 Ohm resistor, then run the amp without the 6080. Use a pair of clip leads to have your meter reading the voltage at terminal 2 while you turn the amp on. If this voltage drops below 130V, then turn the amp off and report back.
I'm not getting a voltage reading at terminal 2. How long should I wait? I don't want to destroy the resistors again. I've left it plugged in for about 6-7 seconds. Voltage hovers around 0.02
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I'm not getting a voltage reading at terminal 2. How long should I wait?
There should be a number on your meter, what is it?
How about the voltages at 21, 15, and 13? Where are you grounding your meter? Is the solder joint where the black wires meet on the headphone jack nice and solid?
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T2: 0.002
T13: 0.005
T15: 88
T21: 178.2
Black is attached to the ground right at the power input.
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Yeah, you have a short. Can you post some build photos? Having the TIP50's installed improperly will give this same issue, but not when the 6080 is removed.
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Here are some pictures. Let me know if there's anything you need to see close-up, or if there's anything I should check.
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Lift the connection between the big Speedball PCB and terminal 2, then recheck those high voltage terminals (with 12AU7 installed).
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T21: 238.5
T13: 232.7
T15: 235.8
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Hmm, now we are getting somewhere. What voltages do you see at terminals 1 and 5 under these circumstances?
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T1: 230
T5: 76
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Well, there's a fault on your big speedball PC board. You can order up a replacement, or take a lot of very detailed photos of the board out of the amp and perhaps we can spot the problem.
-PB
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Thanks. Will these help?
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Any chance to troubleshoot the board as is?
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I would replace the whole board. The only connection from the high voltage DC to that board goes through some high impedance resistors to the LED's, then to ground. Having the high voltage section short out is almost always an issue of proper mounting of the TIP50 transistors, which can be confirmed by pulling the 6080 tube and observing that the problem goes away.
In your case, that doesn't happen. That leaves us with a wiring or component installation mistake that has never been made before in the history of the Speedball, or potentially the wiring of the 8 pin socket is such that the original build would've produced the same problem. There's also the potential problem that the base guiding pin has broken off of your 6080 and it isn't being properly inserted, which is creating the short.
Sending the amp in for repair is also another option in this scenario.
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Thanks, will do. Any advice on what to do once I've installed the new board? Should I fire it up right away or test voltage without the 6080 in first?
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You could test without the 6080 to see if the B+ is still being dragged down.
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OK, new board installed. I'm still getting strange voltages.
1: 174.5
2: 181.1
3: 0
4: 181.1
5: 77.4
6: moves about 0.02 or so (not steady)
7: 171.8
9: 89.6
10: 0.02 (unsteady)
12: 0
13: 180.5
14: 0
15: 203
18: 90.5
19: 91.1
20: 0
21: 218.6
A1: 77.2
A2: 0
A3: 1.575
A4: 0
A5: 0
A6: 173
A7: 14.23
A8: 0
B1: 172.6
B2: 181.1
B3: 172.1
B4: 77.1
B5: 181.1
B6: 89.5
B7: 0.015
main board
B+: 180.7
O: 171.7
left small board:
O: 192.7
I: 200.6
right small board:
O; 77.2
I: 200.6
Note: I did install the silver, round transistors with only about a millimeter gap from the board. I know I should I have given them more. Hope this isn't a source of the problem.
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You're back to having one of the C4S boards up front that isn't working properly (bad voltage at T1 or T5). You'll need to troubleshoot this first.
You many also want to consider removing the Speedball and checking to be sure that the stock Crack is still functional.
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OK, I finally got around to removing the Speedball. Back to stock. Resistances normal. On voltage check I noticed one of the LEDs (the one at A8 to center) was out. So I replaced it. Then it worked. However.... it went out after about 3 minutes or so at which point the voltages started going haywire.
I woke up this morning and decided to replace both LEDs as well as a couple wires I had nicked. That did it! Crack back up and running!
I'm going to wait to put the Speedball in the other Crack I'm building. I suspect it will work fine, since the error seems to have been with the LED.