Hi All,
It is I, the novice of interesting mistakes. I am in the completion phase of my Nutube B! build. I have soured my own parts except for the transistors from the DIY audio store and built mu own chassis. I added a 3rd input to better fit my system. At power up, the nutube lights up on the left side, but does not on the left. All voltages check out except for T8 which has zero volts. T7 is at about 12.7 volts turned all the way down I know I may have damaged the R1 resistor closest to T8. Does that sound like my issue?
BTW, I have done a close exam of all of my solders unter magnification. The power section is as the build guide describes. There is no smoke escaping. I will attach a pic with my eyeball phone.
Any ideas welcome.
Thanks
It is I, the novice of interesting mistakes. I am in the completion phase of my Nutube B! build. I have soured my own parts except for the transistors from the DIY audio store and built mu own chassis. I added a 3rd input to better fit my system. At power up, the nutube lights up on the left side, but does not on the left. All voltages check out except for T8 which has zero volts. T7 is at about 12.7 volts turned all the way down I know I may have damaged the R1 resistor closest to T8. Does that sound like my issue?
BTW, I have done a close exam of all of my solders unter magnification. The power section is as the build guide describes. There is no smoke escaping. I will attach a pic with my eyeball phone.
Any ideas welcome.
Thanks
A new problem...
Hi Again,
I really like this preamp, but a problem has come to my attention. The preamp has a buzz/hum on the left speaker channel. I have isolated to to the preamp. It is always there bur only noticeable at low levels or when the system is on but not playing anything. It does not change with changes in volume. I am going to open it up tonight and look for obvious stuff like cold solders. Other than that, I do not have any knowledge about diagnosing this problem. So if you have a strategy for diagnosis or would like to help me with this issue, please let me know.
Hi Again,
I really like this preamp, but a problem has come to my attention. The preamp has a buzz/hum on the left speaker channel. I have isolated to to the preamp. It is always there bur only noticeable at low levels or when the system is on but not playing anything. It does not change with changes in volume. I am going to open it up tonight and look for obvious stuff like cold solders. Other than that, I do not have any knowledge about diagnosing this problem. So if you have a strategy for diagnosis or would like to help me with this issue, please let me know.
Hum is tough. Pics of the completed pre-amp with the enclosure and all final wiring would be super helpful.
When you say it's on the left channel and isolated to the preamp, is it correct to say that:
- both inputs connected to a source and both output channels connected to an amplifier that you get hum in the left speaker?
- source disconnected from KB1 and both output channels connected to an amplifier, you still get hum in the left speaker?
- source connected, right output disconnected, left still connected to amplifier, you still get hum in the left channel?
- source disconnected, right and left outputs swapped to amplifier - hum moves to right channel?
- hum is not "volume knob" dependent no matter what?
Glad you're liking it!
When you say it's on the left channel and isolated to the preamp, is it correct to say that:
- both inputs connected to a source and both output channels connected to an amplifier that you get hum in the left speaker?
- source disconnected from KB1 and both output channels connected to an amplifier, you still get hum in the left speaker?
- source connected, right output disconnected, left still connected to amplifier, you still get hum in the left channel?
- source disconnected, right and left outputs swapped to amplifier - hum moves to right channel?
- hum is not "volume knob" dependent no matter what?
Glad you're liking it!
Pic of my KB1
Here is the most recent picture.
Tonight I went over everything under as much magnification as I could stand. I cleaned up a couple of iffy solders. I also found that G2 on the nutube just does not like to take solder. I cleaned it up and resoldered it. I sucked off the extra that seems to just want to run down through the hole and cool on the contact close to the actual nutube. It is weird. I am afraid to apply any more heat.
So I plugged it back in and it worked exactly the same.
The evil Hum is still there. It is more volume dependent than I had previously noted. It turns into more of a buzz at higher volumes. It never goes away even with the volume all the way down.
Any ideas?
Here is the most recent picture.
Tonight I went over everything under as much magnification as I could stand. I cleaned up a couple of iffy solders. I also found that G2 on the nutube just does not like to take solder. I cleaned it up and resoldered it. I sucked off the extra that seems to just want to run down through the hole and cool on the contact close to the actual nutube. It is weird. I am afraid to apply any more heat.
So I plugged it back in and it worked exactly the same.
The evil Hum is still there. It is more volume dependent than I had previously noted. It turns into more of a buzz at higher volumes. It never goes away even with the volume all the way down.
Any ideas?
Can you take a close up picture of the input selector switch? You have input grounds attached at different points than the output grounds (to the volume control).
I never connect input grounds to the selector switch, I solder all the left grounds together and the right grounds together and connect them to the PCB input ground points for left and right along with the volume control ground points.
Then again, I've never tried selector switches that switch hot and ground on each input.
I never connect input grounds to the selector switch, I solder all the left grounds together and the right grounds together and connect them to the PCB input ground points for left and right along with the volume control ground points.
Then again, I've never tried selector switches that switch hot and ground on each input.
The hum/buzz is present with no inputs connected and it changes sides when I switch the output cables. So I believe it is on the right channel between the power section and the output. The biggest difference that I can find is that the G2 pin on the nutube is very difficult to solder. I also damaged the lead on the R1 resistor closest to T8. That seems to be working okay, but could the repair cause a buzz?
Last the voltages at T7 and T8 are higher than I would expect based on your article on this project. Both have a minimum voltage of around 13.
That is all I can find. Any ideas?
Last the voltages at T7 and T8 are higher than I would expect based on your article on this project. Both have a minimum voltage of around 13.
That is all I can find. Any ideas?
If all connections are the same on both sides, and all resistor values the same, and active components the same, this would indicate a bad part or one or more bad solder joints.
Bad joints are easier to fix than bad parts, the latter needing some detective work.
Having had experience with joints not taking solder in my own first project, And looking at some of your joints, I would recommend you focus first on resoldering.
First: what cleaning fluid did you use? Ime, isopropanol is king. Some of the industrial spraycan fluids leave some kind of polish crap residue that makes further soldering nigh impossible.
Then: Do you have replacement solder tips?
Then: do you have liquid flux, or better still: creamy gooey oldstyle flux?
Then: do you own a tip renewing paste?
With proper cleaning, and proper tip, and flux - a lot, resoldering that most difficult joint should be possible. If you focus on not touching the Nutube leg and only the solder island, you should be able with flux to fix the joint you might have to remove the old solder, taking care of temp. First heat island, then move tip to part leg.
I would then resolder several other joints, including the output joints. It looks like you had insufficient flow and used very little solder.
You can sort of test the solder joint by using beep mode on your DMM, putting one probe on top of solder, the other on the next solder island/point on the PCB, to verify conductivity and little resistance.
Once properly soldered, if problem is not gone, I would continue to grounding, then active components, then passive. But, if gnd is same on both chans now, verified, that should not be your problem since one chan is quiet.
Haven’t built the B1K myself, but that’s my advice.
Regards,
Andy