Re-flowing the solder?

[IBSTORMIN]

I bought an Integra M-504 amp a couple of years ago from a guy who claims he had a shop service his amp and re-flow the solder on the circuit boards. Said he does it all the time and it makes them sound better. He even produced a receipt showing he paid over $200 to have it done. I bought it at average price or I would not have bought it but re-flowing the solder sounds hokey to me. I took the cover off when I received it and it looked like it had at least been cleaned very well. I've never heard of re-flowing the solder on a circuit board. Was this guy sold a bill of goods by the service shop or is there such a thing?

[mlsstl]

I've seen that technique used to rescue computer motherboards that have developed hairline cracks in traces. The more common subject is a laptop that has developed stability problems caused by the flexing from constant motion. It is basically impossible to resolder individual leads and traces on the densely packed PC motherboards so reflowing the solder is a last-ditch try to save the unit.

You can find examples (including U=tube video demonstrations) on the internet.

As far as audio equipment goes, I'm not convinced the technique would improve the sound of an otherwise operational unit. First, fine audio equipment - and amps in particular - are not typically subject to the constant handling that a laptop suffers. So you are unlikely to have the mechanical stress damage the technique addresses. I suppose it could help if a solder joint was inferior from the git-go but such an amp shouldn't have made it past quality control.

While the technique of reflowing is legit, I am skeptical of any benefit for an otherwise operational piece of audio gear.

[02audionoob]

How would one go about re-flowing the solder?

[mlsstl]

How would one go about re-flowing the solder?

The process I've seen for computer boards involves the very careful use of an industrial heat gun (think hair dryer on steroids) along with appropriate preparation of the board (using foil to cover any plastic that might melt or warp.)

Here's the U-Tube video link: http://www.youtube.com/watch?v=vR8L3B3eDr0

This is probably not for the faint of heart.

[Rich-n-Texas]

I agree with mlsstl. Re-flowing solder connections may help extend the life of the PCB connections, but a noticeable difference in SQ isn't likely.

When I brought my sub home and turned the amp on, I saw a spark and heard a pop. I took the amp off and brought it to work and asked an engineer to look it over when he had the chance. He told me he found a cold solder joint with most of the solder missing, resoldered it and gave the amp back to me. I took it home, reconnected it and all has been well since. Of course, I should've found the problem myself, but I was happy nonetheless and expressed my gratitude.

[bfalls]

I would be concerned using an industrial heat gun. PC boards have ICs of which many are heat sensitive. Originally PC boards are wave soldered where the board and it's components are fluxed (yes I said "fluxed") then travel across a pool of solder. The temp of the solder and timing are set so the amount of heat getting to the components is calculated.

Just heating the board with a heat gun could cause more harm than good. It's necessary for both the component lead and solder to be at a temperature which allows the solder to flow. If the lead is not heated properly a cold solder joint is likely. Multiply the possibility by hundreds of components and it's unlikely the procedure will make the board sound better.

[Rich-n-Texas]

Well here I go getting wishy-washy. I use controlled heat soldering irons (Hakko) here at work and they're very good at maintaining heat stability on the Verification and Engingeering Debug boards I work on. My rework room is a poor-man's type of setup, so there are occasions where I have to use a heat gun when pulling chips off. Whenever possible, I mask exposed areas with capton tape so as to prevent surrounding components from falling off.

Neverthelees, I'd say we all agree that resoldering connections will provide no SQ benefit.

[mlsstl]

If you look at my original response on the issue, I described reflowing solder as a "last ditch attempt" to rescue a laptop motherboard that is having so many problems that it would otherwise be consigned to the junk pile.

To my mind, one would have to be rather foolish to use this technique on a piece of equipment that is working fine in an attempt to subtly improve sound. There are many other tweaks that are far safer, so it might be wise to try them first.

[02audionoob]

The reason I asked is that in buying used audio equipment I occasionally get a component with a cold solder joint somewhere. I just figured there might be some simple home remedy.

I am probably among the faint of heart when it comes to poking around in classic Marantz gear, but I have twice run into components where the interconnects worked correctly only if under a constant pressure, such as can be caused by tucking the cable under or something like that. I've also had an occasion where a power light operated only when pressure is applied. If it was as simple as blowing heat on it, I might be willing to try it. I'm a little bit of a fraidy cat when it comes to poking a soldering iron in there, since I was never any good at Operation.

[mlsstl]

I've built and repaired a lot of audio equipment over the years. I've got an oscilloscope, harmonic & IM distortion analyzers, frequency generators & counters and so on. I've got zero fear of taking a soldering iron to a traditional piece of audio equipment to replace a part or fix a cold solder joint.

There is a big difference between that and using a 1000 degree industrial heat gun on the entire circuit board of a piece of equipment that isn't broken. ;-)

[luvtolisten]

I agree with mlsstl, if it aint broke don't fix it. I spent 30 years with a major company as an electronic technician. Resolder was useful on older devices, built 10 years ago or so. Back then solder had a corrosive fulx,(an acid) incorperated in the solder. The idea was to clean the contact as they were soldered.Unfortunately since it was a corrosive, there cases of eventual bad solder joints after time. Today's solder that is no longer true. Boards can be cleaned by rinsing in water. The flux now is no longer as corresive. Clean up now is like oil based paint vs. latex.The old days, you had you use a flux remover after soldering. Not to say there can be still be cases of bad solder joints, but it's not as common as it once was. Usually the culprit to degrading sound is a component, usually a capacitor, used for filtering. So, to answer your question, resoldering the whole board is more like a last resort to repair a problem that cannot be seen, either by eye or tests. To do it as a routine thing, is like getting a heart transplant every few years. You could end up better, or worse, more likley, the later.