Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: carlman14 on May 27, 2019, 09:04:46 AM
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Well... Here we go. A while back I ordered a new 6080 for my crack, a Thomson-csf 6080wa, as I've heard good things about it. I plugged it in, and the right channel wasn't coming through. I thought it was a bad tube, so the website kindly sent me another. This one worked great, and sounded great too!
Fast forward to the next day, I turn on the crack, and about 10 seconds in, there's a large POP inside the working 6080. I knew that was bad news. Sure enough, I put on my headphones and the right channel was out again. Since my headphones were plugged in this time, I wondered if they were damaged. Sure enough, I plugged in to a different headphone amp, and the right channel is audible, but really low volume.
For troubleshooting purposes, here's a few notes:
- The replacement 6080 I received worked wonderfully the night I got it.
- The RCA tube I had been using for months before this worked without issue.
- It always is the right channel that is either gone from the get-go or goes away after the "pop" sound from the 6080.
- I haven't tried plugging in my RCA tube again. Too scared to do that.
- To be clear, the Thomson-csf 6080wa is a compatible tube, correct?
Where do I even start with this? I've loved the crack so much that I've been debating getting the crackatwoa. Should I just jump ship and buy that instead of trying to debug this?
Thanks,
Carl
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Start by plugging the RCA in and checking your voltages. It's entirely possible that there's an issue in the amp that's causing this and that the tubes having nothing to do with what you're experiencing.
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I'll do that. Just to be clear, I'm testing voltages with both tubes and the rca plugged in, correct? Does the rca have to be plugged into anything on the other end?
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I think he meant your RCA tube
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Oh... Duh. That's my bad. I'm a bit flustered with this whole thing and apparently am not thinking that clearly lol.
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Start by plugging the RCA in and checking your voltages. It's entirely possible that there's an issue in the amp that's causing this and that the tubes having nothing to do with what you're experiencing.
I figured it was the amp, not the tubes. I just find it odd that the RCA would work for so long but 2 (3 actually) Thomson tubes are having problems with the amp. The pop and flash inside the one Thomson 6080 has me the most worried. I don't want to kill any more headphones.
I checked both resistances and voltages. Everything looks ok.
Resistances:
1: *
2: *
3: 0.1
4: *
5: *
6: 0.6
7: *
8: 0.1
9: *
10: 0.1
12: 0.2
13: *
14: 0.2
20: 0.2
22: 0.2
B3: *
B6: *
Left RCA center: 98.5
Left RCA ground: 0
Right RCA center: 89.5
Right RCA ground: 0
Large board
OB: *
OA: *
Voltages:
Small board:
OA: 70.5
IA: 185
B-A/B: 0.4
IB: 184.6
OB: 70.3
Large board:
OA: 99.2
OB: 100
G: 0.6
B+: 184.8
All LEDs are lit.
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I would strongly suspect that there's a flaky solder joint at work here. To kill your headphones, it would most likely be the junction of the black wires on the headphone jack, which is a super common issue. In order to check this, you will want to pull on each wire to see that it is really well soldered on that bottom inner lug. Also check the rest of the connections on the headphone jack to be sure they are nice and snug.
If all else fails, do feel free to post some photos and we can look things over.
There is nothing at all unusual about having a flaky connection not avail itself to you on your schedule, that's just how this stuff works. Changing tubes probably jostled the wires just enough to cause the problem to be much more obvious.
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Alright, I'll look at that joint. I'll get some pics too. Until then, just for the record, here's a couple other points I should mention. Maybe it will help with debugging this:
- I've seen the flash and pop in a different 6080 (GE I think?) in the past. I just chalked it up to a one-off thing, as my headphones were ok, and the tube seemed to work fine still. Now that this happened again, I need to look at it seriously now.
- I installed a triad C-7X choke to replace the resistor going from 13 to 15.
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I tugged at all the wires connected to the headphone jack, and they all feel really solid.
Here are some pics: https://imgur.com/a/W0epJn4
Let me know if there's anything you want a better picture of.
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What kind of solder did you use for the build and which soldering iron?
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I used a kit very similar to this: https://smile.amazon.com/Vastar-Soldering-Iron-Full-Welding/dp/B01712N5C4/ref=sr_1_18?keywords=soldering+iron&qid=1559063480&s=gateway&sr=8-18
The kit came with 60/40 tin/lead rosin core solder. When that ran out, I switched to this: https://www.doitbest.com/products/326070
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OK, I was looking at your joints and they looked like they could've been made with lead free solder or a soldering iron that wouldn't get hot enough. Ultimately I think you may just want to hold your iron on some of your joints for a little longer to let them flow out a bit more.
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Will do. I invested in some flux recently too, so I'll touch up some joints with that as well. The tube that popped... is it safe to plug it back in after I re-flow some joints? I want try and see if the tube is still functional.
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Sure, you can do that. I would just use a cheap pair of headphones if you have concerns about operation.
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So I'm pretty new to tubes. The more I've been researching, the more I've found that some tubes "arc" as they're warming up, which can create loud pops in headphones and blow out drivers. I've seen people generally recommend letting the tubes warm up for 10 minutes before even plugging headphones into the amp because of this. I usually turn on the amp with my headphones plugged in and just give it a minute or two before putting them on my head.
I re-flowed and re-soldered a lot of my joints, but I'm wondering if this could just be normal tube warm-up behavior, and I was just ignorant to certain "tube etiquette", such as letting them warm up all the way to avoid arcs with headphones plugged in.
Thoughts?
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Nope, a tube arcing over at startup is not normal. It is the indication of either a bad tube or some problem in the circuit. That said, it is not a bad idea to start the Crack up and let it warm up for a bit before plugging in headphones if you are unsure of the amp's or tube's behavior.
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Gotcha. Not much else to blame except my soldering skills ;D
If anything, this has been a good learning experience. Thanks for the response.