taiwan ebay sine inverters -- crap or good?

 I've been seeing these on ebay a lot

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item00184187331

at first they were all listed from Taiwan, but now I guess they are
shipping from California.

I need a sine inverter -- my crappy square wave inverter gives interference
on some of my monitors.

Also I like a clear radio signal etc.

Any experience?  I'm sure they aren't all that hot, given the price, but
will they do?

cheers

-z

 

It's probably OK - All of the other ChiCom inverters I've tested have been.  But
geez, $30 shipping?  Sleazebay at its worst.

Before you spend that kind of money AND take the efficiency hit (not a big hit
but..), you might want to get your hands on a good multi-stage LC type EMI
filter.
Most of the surplus houses seem to have 'em all the time.

This type of filter is basically a 60 hz low pass filter that chops off the
higher
harmonics that accompany the pseudo-square wave.  If you look at the output on an
O'scope, the edges of the square wave will be rounded significantly and the
overall
signal will look much more like a sine wave.

This solution has almost always worked for me to get rid of hum lines and buzz
in the
audio and is much cheaper than a new inverter.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
Multitasking: Reading in the bathroom!

 

heh yeah.  One did go for $125 recently so even with the shipping .. its
not so bad.  


I'll check that out.  Not sure what a surplus house is   -- I live in the
serious boonies. Army surplus?

But I've got friends in civ maybe they can find me one, or on the
internets

cheers

-z

 

like one of these?
Filter Concepts Inc model CF151F (CF151-F) EMI filter, rated for 115VAC,
15A input

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item (0186721967

 


No, electronic surplus.  candhsales.com, surpluscenter.com, etc.


That would be a good one to try.

If you look here:

http://www.filterconcepts.com/ac_filters.html

You can get a good overview of filters.  Look at

http://www.filterconcepts.com/ac/sf_series.html

vs
http://www.filterconcepts.com/ac/sw_series.html

The first is a mid-level filter and the second is a high performance unit.  Look
at
the bottom of each page at the insertion loss at 50khz (0.050 Mhz).  The more the
better.  The line/line spec of the high performance filter of 50dB means that it
is a
brick wall to 50 khz.  It'll have considerable rolloff by probably the third
harmonic
of 60hz.  You'd get something that looks pretty much like a sine wave out of it.

The sleazebay one shows an insertion loss of 20dB at 20khz (why can't they keep
the
frequency uniform?)  That's quite good and may approach the performance of the
high
performance filter above.  It would certainly be worth $30.

If you look at others at various surplus houses, you'll see that most of them
have a
diagram printed on the case that looks similar to the "schematic" in the above
pages.
Absent any other spec, the more stages (combo of choke and caps) the better.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
time. -Robert Half