I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

I tore it apart the other day and after removing it from the aluminum
case, I carefully checked for loose solder joints, using a magnifying
glass, wiggling parts, looking for any burnt or other obvious bad parts.
Everything looked ok.

With it out of the case, I plugged it in, and found it worked perfectly.
I used it numerous times out of the case, and it worked each and every
time. However, I was careful not to load it too hard, because the case
is used as a heatsink, and outside the case, the transistors are not
heat sinked, and I could feel them getting warm, but not hot, becuase
the load was low.

After several days of working perfectly, I put it back in the case, and
immediately it failed to work. I was careful to make sure the power cord
was not applying pressure to the circuit board, and everything else was
correctly mounted into the case.

One thing I noted is that the board slides into slots on that molded
alum case, and there are solder joints extremely close to that edge.

My thinking is that even though it worked fine for years, one of them
solder joints is touching the case and grounding out. But why it did not
do that in the past makes little sense. If I could, I'd put some
electrical tape along that edge, but it slides into a groove with no
spare room.

Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine. However, that one
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled". Besides annoying, I
often use these inverters when I go camping, with a portable 12V
battery, and having this think scream in the middle of the night is not
acceptable. Needless to say, I'm returning it for a refund.

So, until I am able to find one without that annoying buzzer, I need to
use my old one. All I can think is to leave it out of the original case,
mount some heat sinks to the transistors and put it into a
non-conductive case, made of plastic or wood.

I am posting this because I wonder if anyone knows what else could cause
it to fail to work inside the case, yet work perfectly outside. The
amount of work and cost of another case is almost not worth all the
trouble to re-case it, but it seems that most of the new ones have those
annoying buzzers. Why they have that, is beyond me, but I refuse to have
to cope with that noise.

In article ,
wrote:
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled".

Simple Answer: 1) Desolder buzzer leg.
Deluxe answer: 2) Put a switch inline with buzzer

Either that or chewing gum strategically inserted to reduce volume ...
--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

Options:

Purchase an inverter that alarms only when actually needed - after all, alarms are there for a reason. Low battery voltage will damage both the inverter and sulphate the battery, altogether a stupid, wasteful idea. Go up to at least 500 watts. Most inverters do not like being run at even 50% of rating. And the incremental cost is tiny. Furthermore, the closer an inverter is run to its rating, the greater the lost-to-use ratio. So, by going to a lower-rated inverter, you are draining your battery that much faster.

https://www.potekelec.com/power-inve...CGIwQAv D_BwE

https://www.amazon.com/gp/offer-list...&condition=new

Purchase 'resist' lacquer and coat both the slots on the case and the traces on the board. This can be done as either a spray or a pen. This may salvage your existing device.

It is really not a good idea from a life-safety position to run an inverter without the cover. A modified square wave is far more damaging than a pure sine-wave - and you are no more than a 10,000 ohm, 1/4 watt resistor assuming you are otherwise entirely healthy with no compromising medical condition.

Peter Wieck
Melrose Park, PA

On Thu, 12 Oct 2017 14:27:20 -0500, wrote:

My thinking is that even though it worked fine for years, one of them
solder joints is touching the case and grounding out. But why it did not
do that in the past makes little sense. If I could, I'd put some
electrical tape along that edge, but it slides into a groove with no
spare room.

Maybe try painting the case and/or solder joints to insulate them?

On 10/12/2017 12:27 PM, wrote:

Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine.

One thing to watch out for is standby current drain.
I've found a huge difference in no-load power consumption of
different inverters.
This can make a huge difference in low-load run time.
Or if you don't turn it off between uses.

On 10/12/2017 12:27 PM, wrote:
I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

I tore it apart the other day and after removing it from the aluminum
case, I carefully checked for loose solder joints, using a magnifying
glass, wiggling parts, looking for any burnt or other obvious bad parts.
Everything looked ok.

With it out of the case, I plugged it in, and found it worked perfectly.
I used it numerous times out of the case, and it worked each and every
time. However, I was careful not to load it too hard, because the case
is used as a heatsink, and outside the case, the transistors are not
heat sinked, and I could feel them getting warm, but not hot, becuase
the load was low.

After several days of working perfectly, I put it back in the case, and
immediately it failed to work. I was careful to make sure the power cord
was not applying pressure to the circuit board, and everything else was
correctly mounted into the case.

One thing I noted is that the board slides into slots on that molded
alum case, and there are solder joints extremely close to that edge.

My thinking is that even though it worked fine for years, one of them
solder joints is touching the case and grounding out. But why it did not
do that in the past makes little sense. If I could, I'd put some
electrical tape along that edge, but it slides into a groove with no
spare room.

Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine. However, that one
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled". Besides annoying, I
often use these inverters when I go camping, with a portable 12V
battery, and having this think scream in the middle of the night is not
acceptable. Needless to say, I'm returning it for a refund.

So, until I am able to find one without that annoying buzzer, I need to
use my old one. All I can think is to leave it out of the original case,
mount some heat sinks to the transistors and put it into a
non-conductive case, made of plastic or wood.

I am posting this because I wonder if anyone knows what else could cause
it to fail to work inside the case, yet work perfectly outside. The
amount of work and cost of another case is almost not worth all the
trouble to re-case it, but it seems that most of the new ones have those
annoying buzzers. Why they have that, is beyond me, but I refuse to have
to cope with that noise.


The transistors are likely insulated from the case. Check for insulator
failure.
Painting the board to insulate it from the slots in the case is unlikely
to last for long. Use something more robust like Kapton tape.

In sci.electronics.repair, on Thu, 12 Oct 2017 14:27:20 -0500,
wrote:


I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

I found out about 20 years ago that power tools need a lot more current
than I imagined, when I was out in the woods trying to use a drill with
a $20 converter. It wouldn't spin at all.

But as to your laptop, or at least as to my laptop, I just use something
that plugs into the cigarette lighter. IIUC there is substantial or
even great waste of power converting DC to AC just so it can be changed
in the laptop back to DC.

Of course how the 12 volts in the car is raised to 19v, I don't
know????? Nor do I *know* if it wastes power but I think it wastes
very little. The one below says, and I haven't measured it but I
believe it, "Power: Input 12V-16V/ 10AOutput: 19.5V 4.62A 90Watt;"

This was for the used laptop I bought this summer:
Car Charger for Dell Latitude 13 131l 2100 2110 D400 D420 D430 D500 D520
D530 D531 D600 D620 D630 D630 XFR D631 D820 D830 E4200 E4300 E4310 E5400
E5410 E5500 E5510 E6400 E6400 ATG E6410 E6500 X300 Xt
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They have them for just about everything.

I haven't tried this one yet, because I'm not taking any car trips until
November, but I used my Acer several times with a similar charger and
everything was fine. I would park in front of a bank, McDonalds, or on
two occasions a hotel and use their wifi. All but one of these times was
at night so there was no place where I could actually go inside, and
come to think of it McDonalds was at 7 or 8AM and they weren't open yet.

But the point is that the power supply worked and the power monitor even
said the battery was being charged.

Also, using this has helped me cut down on my smoking.

In sci.electronics.repair, on Thu, 12 Oct 2017 22:31:03 -0400, micky
wrote:


This was for the used laptop I bought this summer:
Car Charger for Dell Latitude 13 131l 2100 2110 D400 D420 D430 D500 D520
D530 D531 D600 D620 D630 D630 XFR D631 D820 D830 E4200 E4300 E4310 E5400
E5410 E5500 E5510 E6400 E6400 ATG E6410 E6500 X300 Xt
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

And only $17.50, so even if I used a converter, I'd want to have this
rathher small thing in case the converter failed.

They have them for just about everything.

On Thu, 12 Oct 2017 15:15:25 -0700, mike wrote:


Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine. However, that one
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled". Besides annoying, I
often use these inverters when I go camping, with a portable 12V
battery, and having this think scream in the middle of the night is not
acceptable. Needless to say, I'm returning it for a refund.

So, until I am able to find one without that annoying buzzer, I need to
use my old one. All I can think is to leave it out of the original case,
mount some heat sinks to the transistors and put it into a
non-conductive case, made of plastic or wood.

I am posting this because I wonder if anyone knows what else could cause
it to fail to work inside the case, yet work perfectly outside. The
amount of work and cost of another case is almost not worth all the
trouble to re-case it, but it seems that most of the new ones have those
annoying buzzers. Why they have that, is beyond me, but I refuse to have
to cope with that noise.


The transistors are likely insulated from the case. Check for insulator
failure.

That's a good idea. I did not think to check that....

Painting the board to insulate it from the slots in the case is unlikely
to last for long. Use something more robust like Kapton tape.

I sort of think that paint would not last long, unless I applied it real
thick. What is "Kapton" tape? I never heard of that.

Although I do my best to keep stuff like this inverter from getting
abused, anything that sits around between the car seats tends to get
tossed around and fall off the seat, and so on. The case is a heavy
aluminum, and it's not dented or anything, but it could have been
pressed tighter to that board, and thus shorted over time.
\
Although inverters are fairly cheap, I hate to toss this one that works
fine outside the case and was always dependable in the past. Not ot
mention it lacks them damn noisy buzzers. Instead a red LED lights if
the battery power gets low. (A much better design).

On Thu, 12 Oct 2017 21:17:31 +0100 (BST), lid (Mike)
wrote:

In article ,
wrote:
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled".

Simple Answer: 1) Desolder buzzer leg.
Deluxe answer: 2) Put a switch inline with buzzer

Either that or chewing gum strategically inserted to reduce volume ...

Yes, that was my first thought, desolder that damn buzzer.... But I kind
of hate doing that on a new inverter, in case it needs warranty repair
or replacement.

On Thu, 12 Oct 2017 15:11:56 -0700, mike wrote:

On 10/12/2017 12:27 PM, wrote:

Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine.

One thing to watch out for is standby current drain.
I've found a huge difference in no-load power consumption of
different inverters.
This can make a huge difference in low-load run time.
Or if you don't turn it off between uses.

I never knew inverters differred in standby current draw, but I did know
they use current with no load on their output. I alwauys turn the
inverter off when it's not in use.

In article , says...
Painting the board to insulate it from the slots in the case is unlikely
to last for long. Use something more robust like Kapton tape.

Or, if the points at which the short might occur can be identified,
countersink the slot at those points.

Mike.

On 10/12/2017 11:38 PM, wrote:
On Thu, 12 Oct 2017 15:15:25 -0700, mike wrote:


Since I need this badly, for medical needs, I decided to just buy a new
one . I got a 400W, and thought that would work fine. However, that one
has a built in buzzer which is loud and extremely annoying. As soon as I
plug it in, it "screams" at me until it's "settled". Besides annoying, I
often use these inverters when I go camping, with a portable 12V
battery, and having this think scream in the middle of the night is not
acceptable. Needless to say, I'm returning it for a refund.

So, until I am able to find one without that annoying buzzer, I need to
use my old one. All I can think is to leave it out of the original case,
mount some heat sinks to the transistors and put it into a
non-conductive case, made of plastic or wood.

I am posting this because I wonder if anyone knows what else could cause
it to fail to work inside the case, yet work perfectly outside. The
amount of work and cost of another case is almost not worth all the
trouble to re-case it, but it seems that most of the new ones have those
annoying buzzers. Why they have that, is beyond me, but I refuse to have
to cope with that noise.


The transistors are likely insulated from the case. Check for insulator
failure.

That's a good idea. I did not think to check that....

Painting the board to insulate it from the slots in the case is unlikely
to last for long. Use something more robust like Kapton tape.

I sort of think that paint would not last long, unless I applied it real
thick. What is "Kapton" tape? I never heard of that.

I'd start by googling it.

Although I do my best to keep stuff like this inverter from getting
abused, anything that sits around between the car seats tends to get
tossed around and fall off the seat, and so on. The case is a heavy
aluminum, and it's not dented or anything, but it could have been
pressed tighter to that board, and thus shorted over time.
\
Although inverters are fairly cheap, I hate to toss this one that works
fine outside the case and was always dependable in the past. Not ot
mention it lacks them damn noisy buzzers. Instead a red LED lights if
the battery power gets low. (A much better design).

In article ,
says...


Painting the board to insulate it from the slots in the case is unlikely
to last for long. Use something more robust like Kapton tape.

I sort of think that paint would not last long, unless I applied it real
thick. What is "Kapton" tape? I never heard of that.

Kapton tape is an amber colored tape that is heat resistant. It has
been used for insulation of some of the two plate type capacitors that
use a screw to move the plates close together.

It is now often used in the SMD soldering to protect the parts not to be
disturbed. I have placed a piece over components and cut a hole over
the part where I want to use the hot air gun.

While not clear, you can still see through it.

On Thursday, October 12, 2017 at 1:04:43 PM UTC-7, wrote:
I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

Cig lighter sockets and plugs (and the fuse holders they may contain) may corrode and otherwise "get weak"

On Friday, October 13, 2017 at 4:18:01 PM UTC-4, malua mada! wrote:

Cig lighter sockets and plugs (and the fuse holders they may contain) may corrode and otherwise "get weak"

They are also limited in capacity by design. For full inverter capacity, you need to connect directly to the battery.

Peter Wieck
Melrose Park, PA

wrote in message
...
I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

I tore it apart the other day and after removing it from the aluminum
case, I carefully checked for loose solder joints, using a magnifying
glass, wiggling parts, looking for any burnt or other obvious bad parts.
Everything looked ok.

With it out of the case, I plugged it in, and found it worked perfectly.
I used it numerous times out of the case, and it worked each and every
time. However, I was careful not to load it too hard, because the case
is used as a heatsink, and outside the case, the transistors are not
heat sinked, and I could feel them getting warm, but not hot, becuase
the load was low.

How old is the car battery?

On Sat, 14 Oct 2017 20:53:44 +0100, "Ian Field"
wrote:



wrote in message
.. .
I have a 300W, 12VDC to 120VAC inverter. It's worked fine in my car for
years, to power my laptop computer, a medical device I need when I am
"on the road", and even some small power tools. Recently it started
acting weird. Sometimes it wont turn on, (LED is lit). Or it keeps
cycling on and off. Often, I have to plug it into the cig lighter in my
car repeated times to get it to work.

I tore it apart the other day and after removing it from the aluminum
case, I carefully checked for loose solder joints, using a magnifying
glass, wiggling parts, looking for any burnt or other obvious bad parts.
Everything looked ok.

With it out of the case, I plugged it in, and found it worked perfectly.
I used it numerous times out of the case, and it worked each and every
time. However, I was careful not to load it too hard, because the case
is used as a heatsink, and outside the case, the transistors are not
heat sinked, and I could feel them getting warm, but not hot, becuase
the load was low.

How old is the car battery?

That dont matter, because I tried it in my car, in my truck, and on my
NEW portable battery, which is fully charged.

On Fri, 13 Oct 2017 13:56:49 -0700 (PDT), "
wrote:

On Friday, October 13, 2017 at 4:18:01 PM UTC-4, malua mada! wrote:

Cig lighter sockets and plugs (and the fuse holders they may contain) may corrode and otherwise "get weak"

They are also limited in capacity by design. For full inverter capacity, you need to connect directly to the battery.

Peter Wieck
Melrose Park, PA

Cigarette lighter sockets which have been used to light cigs, always
make poor connections. They are full of carbon, ashes, and other crap.
Back when I smoked, I had to regularly replace the lighters. They never
lasted long. Several times I had to replace both the lighter and the
socket.

The one in my car was never used as a lighter, so it makes a fairly good
connection. My truck has 3 sockets. One contains a lighter, the other
two are only for plugging stuff in. That was a good setup. Most (or all)
new cars dont evne have cig lighters anymore. I guess they figure that
everyone on earth has quit smoking.... But they dont consider that those
sockets have other uses. New cars have USB connectors, but they have
limited uses. I'd rather have a 12V Cig lighter socket. Those USB plugs
that go into cig lighter sockets only cost a buck.

wrote:
On Fri, 13 Oct 2017 13:56:49 -0700 (PDT), " wrote:
On Friday, October 13, 2017 at 4:18:01 PM UTC-4, malua mada! wrote:

Cig lighter sockets and plugs (and the fuse holders they may contain) may corrode and otherwise "get weak"

They are also limited in capacity by design. For full inverter capacity, you need to connect directly to the battery.

Peter Wieck
Melrose Park, PA

Cigarette lighter sockets which have been used to light cigs, always
make poor connections.

As does anything that's been around awhile. Wireless chargers are out now (for iPhone X and Samsung Galaxy 6 and later). You simply put the phone on its surface and its ready to go about an hour later.