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newbie solder question

S

Smitty Two

Jan 1, 1970
0
BTW, one use for the flux--I use the paste stuff, must try the
liquid--is to 'activate' old desoldering braid. When doing a lot of
work on old boards, I keep the tin of flux open, heat the braid and dip
the end into the flux between uses. It activates the braid and makes
for much easier desoldering.

Is that also the way to use the liquid stuff? It would probably be a
less messy than my procedure.....

jak[/QUOTE]

I manage a small electronic assembly company, so I've been intimately
involved with soldering on a daily basis for more than 20 years. I don't
know a hell of a lot about troubleshooting, but I know how to solder. We
use liquid flux in little 2 oz. plastic squeeze bottles with 0.010"
inside diameter needles. A drop or two of flux goes a long, long, way
towards making beautiful solder joints, painlessly, and very fast. For
single sided boards, a drop is fine. For double sided, a drop will flow
through the hole and take the solder with it. For desoldering double
sided, put a drop on top and one on the bottom. If you haven't used it,
you haven't experienced soldering.
 
A

Arfa Daily

Jan 1, 1970
0
Smitty Two said:
BTW, one use for the flux--I use the paste stuff, must try the
liquid--is to 'activate' old desoldering braid. When doing a lot of
work on old boards, I keep the tin of flux open, heat the braid and dip
the end into the flux between uses. It activates the braid and makes
for much easier desoldering.

Is that also the way to use the liquid stuff? It would probably be a
less messy than my procedure.....

jak

I manage a small electronic assembly company, so I've been intimately
involved with soldering on a daily basis for more than 20 years. I don't
know a hell of a lot about troubleshooting, but I know how to solder. We
use liquid flux in little 2 oz. plastic squeeze bottles with 0.010"
inside diameter needles. A drop or two of flux goes a long, long, way
towards making beautiful solder joints, painlessly, and very fast. For
single sided boards, a drop is fine. For double sided, a drop will flow
through the hole and take the solder with it. For desoldering double
sided, put a drop on top and one on the bottom. If you haven't used it,
you haven't experienced soldering.[/QUOTE]

Have you had to have a go with this hateful lead-free stuff yet ? If you're
a soldering professional, used to lovely shiny joints that'll see you out to
the grave, this stuff is gonna make you weep ...

If you only assemble for the US market, I guess that you're not going to
have to get to grips with it ( at least not yet ) as the US has sensibly
declined to get involved for the moment, but if any of your products are
destined for Europe, or one or two other places that have signed up to this
particular piece of eco-nonsense, then you're soon gonna be finding out
alllllllll about it .... :~{


Arfa
 
S

Smitty Two

Jan 1, 1970
0
Have you had to have a go with this hateful lead-free stuff yet ? If you're
a soldering professional, used to lovely shiny joints that'll see you out to
the grave, this stuff is gonna make you weep ...

If you only assemble for the US market, I guess that you're not going to
have to get to grips with it ( at least not yet ) as the US has sensibly
declined to get involved for the moment, but if any of your products are
destined for Europe, or one or two other places that have signed up to this
particular piece of eco-nonsense, then you're soon gonna be finding out
alllllllll about it .... :~{


Arfa

That research project is rapidly moving to the top of my list of
priorities. Some of my customers distribute worldwide, and are starting
to make lead-free noises. I haven't seen the stuff personally just yet,
but I've heard reports similar to yours.

I'm generally very eco-minded, and don't mind making sacrifices to
retard the speed with which mankind is destroying what's left of the
planet, but I'll agree that the logic on which *this* regulation is
founded seems a bit shaky.

Since you brought it up, maybe I should start now. Do you have any
specific suggestions as to choices of solder and flux, methods,
equipment, cleaning considerations, primers I should read, etc? Or is
lead-free simply an inferior "drop-in" replacement that doesn't mean I
have to change everything else?
 
A

Arfa Daily

Jan 1, 1970
0
Smitty Two said:
That research project is rapidly moving to the top of my list of
priorities. Some of my customers distribute worldwide, and are starting
to make lead-free noises. I haven't seen the stuff personally just yet,
but I've heard reports similar to yours.

I'm generally very eco-minded, and don't mind making sacrifices to
retard the speed with which mankind is destroying what's left of the
planet, but I'll agree that the logic on which *this* regulation is
founded seems a bit shaky.

Since you brought it up, maybe I should start now. Do you have any
specific suggestions as to choices of solder and flux, methods,
equipment, cleaning considerations, primers I should read, etc? Or is
lead-free simply an inferior "drop-in" replacement that doesn't mean I
have to change everything else?

Smitty

Mail me direct and I'll sort you out some links and articles.

Arfa
 
D

default

Jan 1, 1970
0
I think I'll solder to the trace on the other side of the board, just means
that the cap won't sit flush anymore but that's okay, lots of room in the
enclosure.


Yes, must buy solder sucker. It's on my list now.

No. Do you mean between the channel A and channel B signal outputs with no
signal applied to the inputs? If there WAS a DC voltage differential what
might this tell me? Failed coupling cap? There are no output caps, the amp
output pin (see below) goes straight to the center pin of the RCA jack on
the back.

Sometimes the DC levels can tell you a lot. No signal - since without
a scope it wouldn't do much good. Check input output ground and Vcc -
don't assume it is connected check it at the solder joint or component
leads. Assume nothing. Believe the voltmeter not your eyes when it
comes to connections.

I don't know if I buy the no output caps and single supply . . .

With class AB (which is your amp) the output of the amp running on a
single supply HAS to be one half the supply voltage with no signal
present. That means the speaker would be driven close to its travel
in one direction at all times if the circuit doesn't have a
transformer or cap to take the DC from the speaker.

The choice is a coupling cap (high value like 400 to 4,000 ufd) in
series with the speaker - or two amps per channel with the speaker
between the outputs. Both amps sitting at 1/2 half the total supply
so the speaker has no voltage differential across it - the amps when
driven are working out of phase to one another - one side becomes more
positive the other more negative. (a technique used in car radios)

The other choice is a plus and minus supply with one side of the
speaker to ground.


http://www.national.com/ds/LM/LM1875.pdf See the application
datasheet for the details of dual/single supply operation - note the
cap in the single supply version . . .

Both the amp and bass/treble/volume/balance IC's run off +Vcc.


TO220 -
One chip per channel. They're LM1875T's, yes they have built-in thermal,
short circuit, etc. As I noted I have already replaced the one on the bad
channel (they are a TO-220 package).

Does it matter if I use an electrolytic or not? See pinout below, but I'd
connect pin 1 of channel A (working) to pin 1 of channel B (dead). If I do
use electrolytics, which end is positive, A or B? Why do I need to use a
capacitor to bridge as opposed to a wire?

It does matter, to the capacitor in particular. Electrolytics don't
tolerate over-voltage or reversed polarity very well. There are
non-polar electrolytic caps, but they aren't common.

The data sheet suggests you use a one or two microfarad cap for input
coupling. A .1 may also work but give some tinny sound quality.

You can "make" a non-polar cap from two polar caps. Take two caps
with the same specs - preferably from the same maker and batch. Tie
either both plus terminals together, or both minus terminals together
- use as you would a normal un polarized cap.

The voltage rating will be the rating of one cap and the capacity will
be 1/2 the value of each cap. (2 X 4 ufd / 25 volts = 1 X 2 ufd / 25
volts)

An electrolytic is usually specified at something like a tolerance of
+100% / -30% of capacity - a loose spec to be sure. The designer
takes this into account and what AC current the cap will have to
transfer at what frequency then allows for tolerance. A point one
microfarad may just sound like there's less bass present.

Likewise if you have a 2,000 ufd speaker coupling cap (as shown in the
data sheet) a working 100 ufd may sound a lot better than a non
working 2,000 . . .

Here's the pinout:

1 +IN
2 -IN
3 -V(EE)
4 OUTPUT
5 V(CC)

Bridge pin one on one amp to pin one on the other with a non-polar cap
(to be safe). You could just touch the terminals with the cap but
that may cause some output noise and it would be safer to clip the cap
in then apply power.
 
D

default

Jan 1, 1970
0
PS turn on thump is almost always a sign of a DC offset in the
output. It may suggest a DC offset in the input to the amp and
carrying that logic further - the built in protection is saving the
speakers from frying.

Some amps do thump when nothing is wrong - the design just comes up in
an unbalance condition and straightens out after a millisecond or two
as caps charge in the input stages.

Check the voltages . . .
 
A

audiodir

Jan 1, 1970
0
I haven't kept up with this thread, but I have been using lead free solder
for over 5 years now. I had to jack up the tip tmeperatures to 700 degrees
in order to get good flow. A touch of standard external flux helps a lot. I
use smaller guage solder also, flows better.
I do keep standard solder on the bench. I once, early on, did an amplifier
repair and the customer who picked it up returned it sayng that the side I
had repaired sounded so much better he wanted me to fix the other side. I
had used the lead free solder on the repair. I replaced the lead free with
standard solder and both sider were equal and he was happy.
I do admit, I hated the lead free in the beginning, but I've become used to
it and can work around it's mlimitations. I do cheap a bit and sometimes tin
old joints with leaded solder before applying lead fee.


Stu
 
L

Leonard Caillouet

Jan 1, 1970
0
Not all lead free solder is the same, though even the best that I have used
is not as good in terms of flow as leaded. The best formulation that I have
found is Sn 96.5, Ag 3.0, Cu 0.5 that I got from Mitsubishi. It only
requires a slightly higher temp than normal, about 30 degrees.

Leonard
 
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