On 11/3/19 2:46 PM, Ralph Mowery wrote:
In article , says...
I'm a big user of eBay and AliExpress, and purchase lots of
high-current and high-voltage stuff, to supplement my pile
of unusual parts, but I'd not come across the items you found.
You have to be careful of the ebay China parts. Seems that many of the
high power and some other parts are not up to what they are suppose to
be.
I have bought some things from China via ebay. Most have been good.
I did buy some RF transistors and they would hardly make any power after
about 7 MHz and replaced them with some RF Parts company and those had
the full power at 30 MHz where I wanted to use them.
Friend bought some rated for about 5 or 10 watts and all 6 of them were
bad from the start. The first 2 he put in fried his circuit. He
measured the other 4 before instlling them and they were all shorted.
I have seen some pictures of the internals of the 2n3055 transistors
from China and some had a very small silicon area compaired to the
'good' ones. They would test good but probably only good for about 1/2
to 1 amp.
It's a shame China parts can be so varying in quality, but I too am not
immune although in a different capacity: faucet vacuum aspirators. I
had a really nice glass one, US made, that would pull up to at least 28"
Hg with standard faucet pressure, then one day my carelessness broke it.
It was a Kimax? and they were no longer available, so I decided to
try a stainless steel aspirator from China. It could hardly pull 15"
Hg, a far cry from the advertised 28-30" Hg! I contacted the seller and
got an immediate refund with no argument, so I'll bet, at least in this
instance, that there were a lot of insufficient aspirators. That wasn't
the only one I tried as I tried out several other metal ones, but none
would pull vacuum like the glass one did. That's when I finally decided
on a single stage pump but, after 2 years, that Chinese made pump has
leaked.