Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: tsuid1 on January 23, 2020, 11:46:32 AM
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Hi all, I posted about this before, but for some reason, the website is giving me a hard time replying and updating, so I decided to post again with more details.
Like the title says, just finished building the crack. I checked the resistance this morning and the numbers all matched the manual's.
Last night I was performing the voltage test with tubes installed. The 12u7 tube glows with no issue but the 6080 doesn't glow at all. The LED's were on for five minutes, but then they turned off and hasn't turned back on since.
The voltage also seems to be pretty low compared to what the manual says. Also worth noting that I checked the orientation of the 8 pin socket and it's pointing towards the vent holes as instructed. As for the L+N voltage test, my meter measured 121v, so I followed the instructions on page 25
1- 2.30v
2- 2.30v
3- 0v
4-2.3v
5-2.3v
6-0v
7-0v
8-0v
9-0v
10-0v
Also added photos below.
Thanks
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You might need to check the file size of the pictures since there’s an attachment limit.
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Just added. Thanks!
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Can you perform the checks on page 29 of the manual?
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Sure. For the first part, I got 6.5v, and 177v on the second part. Looks like the numbers are in range
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Are the tubes glowing?
20U and 21U do not look to be all that well soldered.
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The 12u7 tube glows but not the 6080. I'll try to add more solder.
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B7/B8 make the 6080 glow. Can you post some photos of your 6080?
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The 12u7 tube glows but not the 6080. I'll try to add more solder.
In addition to a bit more solder, it may be necessary to add a bit more heat to the junction so the solder flows nicely leaving a clean and shiny joint behind. Higher heat for a shorter period of time is often an effective approach if you have the ability to adjust the temperature of your soldering iron.
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Here are some pictures of the 6080, 8 socket and 20u and 21u.
Does this mean I have to reheat the solders at 20u and 21u? How long should I reheat them for? I just checked them and they were both filled before I resoldered anything.
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Just a few seconds should do it, usually not more than 4-5s depending on the overall mass of what you are trying to heat. It you watch carefully with a bright light, you'll see the solder melt when you apply the iron and you'll also see the melting spread across the solder joint as you heat it. If you need to add more solder, this is the time. Then, just remove the iron and let it cool on its own and you should be good to go.
If you have any doubts, there are TONS of youtube videos about forming proper solder joints. If you are new to soldering, it sometimes takes a little bit of practice, but you'll get it!
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Ok, before I had a chance to solder, my dad who is an electrician checked on the wiring. Everything seemed fine, but we found that the 5w 270ohm resistor by terminal 13 and 14 is open. Could this explain why the amp isn't working properly aside from soldering those two joints?
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... we found that the 5w 270ohm resistor by terminal 13 and 14 is open. Could this explain why the amp isn't working properly aside from soldering those two joints?
Yup. With an open 270R resistor, you'll have no high voltage power supply. You'll want to replace that resistor.
cheers, Derek
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Definitely replace that resistor. Any 200-300 ohm 5W resistor will do.
Also do post photos of the 6080 you have in the meantime.
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Sure no problem. Images are below.
Just contacted the replacement service. Hopefully will have it by Saturday. I'll probably try to look for it in a local hardware store. How much does it usually cost?
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I'm curious why a 5w sandcast resistor is open... That's a pretty beefy resistor and I've never come across one that was DOA before usage. Proceed carefully and check voltages and wiring as thoroughly as possible. There may be a fault somewhere that caused that resistor to burn up. If there is a problem, installing a new one will simply lead to it burning up as well.
If you don't find an obvious wire fault, keep an eye (a temp probe? a finger?) on that resistor for the first minute or two after you power up to look for "extra" heat. Given that it's a B+ smoothing/dropping resistors, a temp of 30-50c might be normal. 30-40c means you can keep a finger on it indefinitely (watch out for the voltage - don't touch the lead!). 50c is a finger on it for <5s or so. I'm gonna guess that you really shouldn't be seeing anything north of 70-80c.
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I thought the same thing, but the open resistor doesn't show signs of having been cooked. The writing on the body is still black, clear and even; and there is no discoloration of the leads from heat stress. Maybe a lead broke/disconnected inside the body - either at manufacture or subsequent twisting?
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Can you measure the DC resistance between pins 7 and 8 on the tube itself?
It is weird that the resistor is open, but I have seen that happen once in the last 25 years.
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Both of the above points (resistor doesn't appear burned and it seems rather rare to a new resistor that is DOA) make me think the problem lies elsewhere. Are you getting good contact with your probes on the resistor leads? Maybe some steel wool or gentle sand paper cleans something off of the leads that was causing a problem?
If this is not the case, your problem is most certainly elsewhere. Search logically and methodically and start with most basic elements. Work from the schematic and with your meter, cross off verified connections and note voltages on the diagram and move on. You know generally where to look. Start with the transformer, verify you're getting good AC voltage into it and good AC voltage out of it. Check fuses, solder joints, voltages at each PSU cap, across the bleeder resistor, etc.
You'll find this - be logical, check every component and every wire, one at a time.
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I'll probably try to look for it in a local hardware store. How much does it usually cost?
Mouser sells them for about a $1: https://www.mouser.com/ProductDetail/Yageo/SQP500JB-270R?qs=%2Fha2pyFaduiKZkvBfzT47gv2toBgzYfDhi5ak38cJcV7ykBbdTaI9Q%3D%3D (https://www.mouser.com/ProductDetail/Yageo/SQP500JB-270R?qs=%2Fha2pyFaduiKZkvBfzT47gv2toBgzYfDhi5ak38cJcV7ykBbdTaI9Q%3D%3D)
A North American hardware store selling construction tools and supplies is very unlikely to carry them. But a local electronics supply shop would most likely have something that would work - and maybe charge a bit more. Maybe 2$. As PB wrote, anything 200-300 ohms and rated 5W will do.
cheers, Derek
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Dang it, yeah I meant electronics store.
I measured the 7 and 8 pins on the tube and got a resistance around 1 ohms.
My dad was testing the voltages and resistance using the schematic, and the only issue he found so far was that dead 270ohm resistor. Right now, I'm going to look for any weak soldering joints, weak resistor probe connections, voltages, sawdust etc. Is there anything else I should look for in the mean time? Do the probes have to be completely through the hole on the terminals if it's connected by solder?
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You have to get the 6080 glowing before you do anything else. If pin 7 to 8 on the tube measures 1 ohm, the tube should glow. Perhaps the green wires running to the octal socket aren't well connected?
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Hi guys, first off sorry for the radio silence, I had relatives over these past few days, so I didn't have time to work on the amp. Customer service got back to me and said the resistor is headed my way.
I've been inspecting the amp, but so far I don't see any issues with sawdust. My dad inspected the solder joints and everything seems fine.
Here are some photos of the green wires
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Neither of those green wires is well soldered to the power transformer. You need to wrap the free end of the wire up and over the transformer terminal, then solder. The solder should flow into the area where the wire is wrapped around the terminal.
Just poking a wire straight through and hoping the solder will make a good connection is not adequate.
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Lots of visual examples of good and bad solder joints:
https://www.google.com/search?q=proper+solder+joint&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiGqZONtqnnAhXjmXIEHbYCD2EQ_AUoAXoECA4QAw&biw=1312&bih=693
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Being able to see a proper solder joint helps alot. I'm going to study up on this before working on it. Thanks!
As for the wires, yeah it looks like I didn't properly wrap and solder the wire around properly. I cut what I thought to be excess wire after I bended and soldered it. I'll probably strip a bit of the coat off and wrap the wire around
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Hi, sorry for the late reply. I haven't had time to work on this until recently. I was able to get the 6080 to glow after installing the resistor. All the voltages are in order. However, I ran into a couple of issues
1. There is a channel imbalance with a bias towards the left side. I checked the inputs and they seemed to be wired correctly. Wetted and added a bit of more solder to the red rca but nothing really changed. There also is a very very low hum in the right side, but I have to concentrate to notice it.
2. I had some issues with the audio. When I listened, the bass was boomy, midrange was dry, treble was recessed, and there was little to no soundstage and depth. I wetted and added more solder to any cold joints I could spot and now it's pretty neutral; midbass has drastically reduced to being linear, midrange is a bit sweeter, and treble is more airy. It sounds identical to the Atom. From what I read, the stock crack is supposedly a warm sounding amp, but I'm not too sure if what I have is right or wrong.
One thing to note is that the black wire connecting the headphone output and terminal 12 is soldered on 12u as opposed to 12L. The new resistor is soldered on terminal 13 and 15 standing up. Would that be part of the issue?
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Re audio/listening issues:
(1) What headphones are you using?
(2) Give the amp time to break/burn-in before doing any critical listening tests. The caps and tubes take time to settle into what will become their normal operating characteristics. To get there, you need to put signal (music) through the amp (with headphones connected or with other suitable load) for at least 50-100 hrs. The sound can change quite a bit during the break/burn-in period. In my limited experience, the bass is the last thing to finally settle. My approach is to run an amp that needs break/burn-in in 12-20 hr sessions - letting the amp cool to room temp between sessions.
Re installation issues: Installing a component on the upper vs./ lower lug, or vice versa, shouldn't make any noticeable sonic difference. Same goes for installing the 270R resistor standing up. But I suspect having the resistor flat against the chassis and away from the caps is much better for dissipating heat. Those resistors get hot and caps don't like heat. PB will be able to tell you whether this is a problem in your case.
cheers, Derek
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Thanks. This is good advice. I'm running them with my HD 600. As far as burn in, I've ran it for about alittle more than 20 hours approximately. I'll let it burn in more
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Your description of what the amp sounds like is how I would describe the sound of cold solder joints.
Channel imbalance is somewhat covered in the FAQ sticky on this board, but also be aware that cold solder joints can definitely cause this too.
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Thanks PB. Are you referring to my current description? I wetted and added solder to any cold joints I could find and the tonality went from dark to neutral.
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Can you post a bunch of photos of the build?
Wetting the joints may not be what you need to do, often what I do is to heat the joint until it flows out, then give it a few more seconds of heat. For everything but the joints where the LEDs connect, this can take a bit of time.
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Here you go. I tried to take as many angles as I could. Apologies if it's a little low on quality. I took the advice from the thread on soldering, but as you can tell it's still not great.
I realize the first joint doesn't have the wire bent correctly, so I'm fixing that as we speak.
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You are either dealing with a soldering iron that won't get hot enough (45W minimum, if it's adjustable, turn it all the way up) or lead free solder. It also helps to wrap component leads and wires around the terminals so the solder has a place to go.
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The earth tag on white input terminal picture 14 is an example of a decent solder joint. i.e. not too much solder, and is smooth and shiny. Try and match this standard throughout.
I can recommend Cardas solder. A little expensive but if you don't solder on a daily basis a small coil like this will do a Crack and Speedball with leftovers. Very easy melt and flow and very nice to use.
https://www.ebay.co.uk/i/162116066532?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=162116066532&targetid=855313181933&device=c&mktype=pla&googleloc=1006618&poi=&campaignid=6619151996&mkgroupid=88031187549&rlsatarget=pla-855313181933&abcId=1140496&merchantid=115579357&gclid=CjwKCAiAp5nyBRABEiwApTwjXrtCnfX1PiXqulglv6DOdNjZauBIZ64ltrTdOnkYQMEdJ4WzpH_1XhoChcwQAvD_BwE
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+1 on Deluk's recommendation of Cardas Quad Eutectic solder. Despite its silver content, in my limited experience it melts and flows more easily than any other solder I've used. For lower temp soldering (e.g., with an iron that doesn't put out many watts), it works extremely well.
Besides price, the only downside I've found to the stuff is that its rosin leaves a brownish crust on the joint. But the crust is easily removed if you don't like the appearance. I usually leave it.