Thread: OT Blue
View Single Post
  #29  
Old March 23rd 17, 07:38 PM posted to alt.windows7.general
Paul[_32_]
external usenet poster
 
Posts: 11,873
Default UPDATE: OT Blue

TrialAndError wrote:
Solved the sound problem on the PC.
I have never in my decades of experience seen this and I work in
electronics all my life.

I have external speakers plugged into the monitor as I said before.
As it turns out, the connector, eitehr plug or socket seems to be faulty.

Usually when there is a bad connection the sound would crackle or cut
out all together.

In this case I got no crackles or anything like that, just that the
volume significantly reduced to a whisper.

So wiggling the connector and in and out fixes the problem for a while.
The it happens again.
Maybe it is not really the connector but the electronics in the speakers.
They are powered, have volume and tone controls.
So maybe it fades and then removing and inserting the plug wakes up the
electronics in the speakers. This is a more likely scenario. Since the
sound on both stereo speakers fades to a whisper.

Look for a new set of speakers now.
Powered
Volume control
Tone control
Balance (maybe)
Good quality sound BUT CHEAP !

Suggestions please.


Test the computer output with headphones. That's to help
you determine the problem isn't on the computer end.

*******

It could be a cold solder joint in the speaker, on the
amplifier board. That's what happened to mine. I ran a
fingernail over the solder joints. Each joint would have
been failed by a trained inspector, so I had to try all
of them because they were done so poorly. (They were all
ball-shaped, and didn't have a curved meniscus.) But, I found the
bad joint and re-soldered it. And the speakers still work today.

Some audio circuits stop working, because the DC bias is upset.
Both the computer output, and the speaker input, use capacitors
and the circuit is "doubly-capacitively-coupled". Normally,
the odds of DC leakage from the computer side, upsetting the
bias point of the speaker input amplifier, would be near zero
odds. But, with poor quality caps from the "capacitor plague" era,
stranger things have happened.

Standard debugging technique (apply stimulus to input, walk through
the design, stage by stage), that's only practical if you have a
schematic. It may not be possible to follow the circuit well enough
by just eyeballing the components on it.

The speakers also need a power source. To drive "watts", the speakers
need "volts". For example, my puny other speakers, the internal
supply on those is around +16VDC. On the stereo I used to have,
it was around +50VDC. You could check the power source and verify
it is quasi-stable. Lots of these things use simple bridge rectifiers
and a large filter cap, to create the power. The circuit is typically
unregulated. If the line voltage goes too high, something can blow up.
Typically cheese-flavored amplified speakers, are at the mercy of your power
company.

My power company here, blew up my stereo, and it was because the
standing voltage on distribution here is wrong. (My 110VAC should
measure 113VAC at the mast, and it regularly rests at 121VAC.) It burned
out my stereo in stages. The display failed. The tuner failed (no more FM).
Then the mixer/remote control failed. Only the amplifying portion
remained, but I couldn't get any signal into it.

*******

You will find buying speakers, to be a difficult process. High power
amplified computer speakers, only seem to last a few years. The low
end stuff, when you read customer reviews, not all the customers
have the same "tastes". That makes it hard to decide whether
the reviews are being truthful about the value of the product or not.
For example, a review may say "OK for the price", you get it home
and there is no output below 200Hz or so. I don't expect miracles
from cheap speakers, but it is possible to get decent speakers.
The ones I got, cost only $20, but they haven't been for sale for
about 10 to 15 years. You can't buy them any more.

If you can go to a local computer store, and try their "demo rack"
of computer speakers. That will at least familiarize you with
how bad some of these things are. Nothing I saw at the stores
here, would I buy. Some were "cute", but didn't sound right.

So I bought a pair of speakers at the "surplus computer" place.
And they turned out to be better than speakers at $100 at the
other computer store. Price means nothing on the low end. You
can pay $100 and get sheer crap. Or pay $20 and be happy.

The problems with the higher end stuff, shows up after you've
been running them for a few years with the volume at 7. The vibration
kills the amp (located inside the Sub). And typically the knobs
or control box or the like, fails. The controls, they just can't
seem to make rugged assemblies for those.

Have fun,
Paul
Ads