[Llama16]

Merry christmas everyone, sorry if I'm a bit to late.

I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered.

would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something.
I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of

 

[dean0]

Quote:

Originally Posted by Llama16 /img/forum/go_quote.gif Merry christmas everyone, sorry if I'm a bit to late. I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered. would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something. I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of

turn up your solder iron, and use plenty of flux, heat the joint for a while before adding solder.

 

[Yaka]

im no expert but judging by the burn marks ( and the well soldered sockets) heat is not the issue lack of flux is.

last i say that was when first soldered some thing 9 years ago, back then i use snip first and then solder and it would end up looking just like that

 

[tomb]

Quote:

Originally Posted by Llama16 /img/forum/go_quote.gif Merry christmas everyone, sorry if I'm a bit to late. I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered. would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something. I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of

Those are some small holes. If you don't get it right the first time, it could be tough going back and trying to get it right.

Yes, a jumper or similar to the other LED's ground lead will work fine - it's all ground, anyway.

 

[Llama16]

Thanks for the help.

It's not my pic btw

i took the one from tomb's helpfull guide.
If I don't get a nice solder joint in a few seconds, then I'm quite sure it becomes a blob. it's like the solder 'floats' on the board and just doesn't want to go in, even if I take most of the solder away with a braid. As if it acts like mercury, that's the best description I can give. I use solder wire with flux in it, and i think that when there is to much flux on the pad itself that it becomes a blob.

After doing a bit of soldering I found that the best way to avoid this is to apply the solder to the iron, and then from the iron to the joint. That way it leaves the excess flux (that keeps coming when applying more of the solder wire) on the tip of the iron. Sadly I only discovered this after trial and error.

When desoldering that wire for the 4th time or so, I got a good contact (0.5ohm resistance, and the 0.5 comes from the multimeter itself) so I figured I'd leave it that way. Hoping it'll stay, because the more I touch it, the more it gets worse. The joint doesn't get alot of stress, but if it happens that a ground for 1 of the 2 leds gets loose, what would be the consequence? Double the current for the other LED? And if so, could that LED take it for a short time (because when I see one of the leds don't work, I'll go back and fix it)?

Thanks for the help everyone

 

[tomb]

I was going to say ... I didn't see any burn marks in that photo.

Yeah, if you lose the ground wire, the other LED will burn brighter. However, the LED resistor was sized for 10ma, so at the worst, the other LED will just be exposed to 20ma - still OK.

On the other hand, your soldering problem could just be a cold iron. If the iron tip is not hot enough to quickly heat the ground pad, then the reliefs won't do much good and the iron will proceed to try to heat the entire PCB ground plane. That's a losing battle and one result will be solder blobs and no stick.

If you can't heat the iron up hotter, then different methods to enhance the heat transfer with all you've got is the best strategy. As you've found, if you have a bit of solder melted onto the tip of the iron, it will spread the heat faster to the pad. You can use this trick while never touching the soldering wire to the tip and still adhering to the principle of solder to the joint - not to the iron. Another method is to use extra flux - nothing wrong with doing that. Get yourself some solder paste, dip the tip of the wire into it to get a 1/8"-14" blob of paste and apply it to the joint. The iron should heat the flux, which melts then spreads the heat quickly throughout the joint. The result is that the solder melts easily and sticks. The downside is that it may take you longer to rinse the board and get it clean from all of the extra flux, but that's a small price to pay for the improved soldering.

 

[Llama16]

(Whoops, double post. I thought I deleted this msg... the one below was better anyway)

 

[Llama16]

Thanks, I'm glad to hear that the other LED won't burn out if I'm mistaken. I'll still be able to fix both if the left one doesn't work.

I really thought that the excess of flux on the solder pad prevented the solder to cover it. I just put my soldering iron to full (was on 4/5 or so), so I don't forget it tomorrow.

BTW: I failed to mention that I'm very happy with the kit. Also, thank you for you help with the lug sockets you gave me.

Dries Fact: The kit got stuck at our famous greedy belgian customs (which btw came with a hefty bill for all sorts of taxes

). But when I just finished studying for my final exam, the doorbell rang and a happy postman came to deliver it. Now that's timing. Couldn't have been happier.

 

[tomb]

Quote:

Originally Posted by Llama16 /img/forum/go_quote.gif Thanks, I'm glad to hear that the other LED won't burn out if I'm mistaken. I'll still be able to fix both if the left one doesn't work. I really thought that the excess of flux on the solder pad prevented the solder to cover it. I just put my soldering iron to full (was on 4/5 or so), so I don't forget it tomorrow. BTW: I failed to mention that I'm very happy with the kit. Also, thank you for you help with the lug sockets you gave me. Dries Fact: The kit got stuck at our famous greedy belgian customs (which btw came with a hefty bill for all sorts of taxes ). But when I just finished studying for my final exam, the doorbell rang and a happy postman came to deliver it. Now that's timing. Couldn't have been happier.

Thanks for the kind comments on the kit.

No, excess flux is never going to inhibit soldering, IMHO. It will only make things messier (but easier, most likely). There's an outside chance that you may use so much flux that it will cool things off, but again IMHO, that's just more of a sign that your iron heat is marginal. Even solder paste should literally vaporize, bubble and boil when hit with the soldering iron. Meanwhile, all that catalizing reaction with the paste and vaporizing/boiling will burn off any surface sheen/finish and ensures that the melted solder will stick.

 

[Juaquin]

Also, if you have a hot air gun you can heat that area to get solder to flow, especially with that huge ground plane. I just built some speakers at home where I only have a ratshack firestarter 20-30W iron and I had to use a heatgun to get solder to flow on the thick copper traces. A blow dryer might be ok in a pinch. Just don't overheat any components.

 

[kdris]

Quote:

Originally Posted by the_equalizer /img/forum/go_quote.gif Sorry for the delay in replying. I don't have access to the forum from the office. getllamasfast: indeed they are intercheangable and, as a matter of fact, I built my 12AU7 version using new, current production JJ 12AU7 tubes. I also tested with 12AX7 (current production Russian Mullard) and 12AT7 (old GE ones) and they work great too; giving you different levels of gain. TomB: actually the modified version I tested and built, based on Dsavitsk's hints, uses the two sections of the triode in parallel, just like the 19J6 version. I wanted to use the 12AU7 precisely because you can get some old ones dirt cheap, some new ones at around $15 USD or some 'boutique' NOS ones at $$$$. So while the current production 12A_7 tubes are not as cheap as the 19J6 was some years ago, at least their price is consistent and they're very easy to find. Oh! After reading the posts again I see what happened... you were thinking about Logistic's 12SR7 version. That one indeed uses NOS tubes (beautiful octal ones ) that are still VERY cheap. As I remember it those are radio tubes that have a triode and two diodes in the same bulb; so there's no way to use the triodes in parallel. cheers!

Equalizer,

If you have a free moment. Is there a link to how exactly the circuit was modified in your 12AU7 version? I've been digging through this thread for a while now and am unable to find it. I know it involves changing resistors R2 and R8 but what are their exact values and how does this affect the circuit as far as pinouts from the original tubes.

Thanks in advance,

kdris

 

[the_equalizer]

Quote:

Originally Posted by kdris /img/forum/go_quote.gif Equalizer, If you have a free moment. Is there a link to how exactly the circuit was modified in your 12AU7 version? I've been digging through this thread for a while now and am unable to find it. I know it involves changing resistors R2 and R8 but what are their exact values and how does this affect the circuit as far as pinouts from the original tubes. Thanks in advance, kdris

Sure. You can find it here. It's (currently) about the 30th post that shows up if you search 12AU7 using the 'Search this thread' feature

cheers!

 

[kdris]

thank you so much for the fast reply!

 

[Llama16]

Little question:
Does flux conduct? Because I don't got anything to remove it, and I don't think I'll find it somewhere near. So I thought I'd just forget about it.

I think I'm right when I say it doesn't, allthough I'd definately clean it off if I could (I'm the precision guy... eg: checking for cold joint ABOUT 15 TIMES OR SO, I know I'm a freak.

 

[tomb]

Quote:

Originally Posted by Llama16 /img/forum/go_quote.gif Little question: Does flux conduct?

Over time, ABSOLUTELY.
Quote:

Because I don't got anything to remove it, and I don't think I'll find it somewhere near. So I thought I'd just forget about it.

Clean it off. All it takes is an old toothbrush, some paper towels and some 90% or better isopropyl alcohol that you can obtain (very cheaply) at any corner drugstore or Walmart. Use the toothbrush by dipping it into a bowl filled with the alcohol. Scrub the entire board until it's completely coated with alcohol and you've scrubbed down the biggest lumps. Pat up the liquid with paper towels. Repeat as necessary (usually takes 4-6 times). Use several rinses until all of the white powder is gone and your paper towels no longer pick up yellow stains.