HAMELECTRONICS MAGAZINE . com                    June 6th 2015

More bad Dual Gate Mosfets out of China !
I ordered some parts from Ebay
and a Chinese Vendor. The 50
LM358P op amp chips seemed to
be good.
I tested them with my tester.

Next.. I tested the 6  BF961s Dual
Gate Mosfets I ordered from the
same company.

The 6 all tested bad. My tester
read "UNKNOWN COMPONENT".

For Comparision .. I tested some of
the BF981s I had around here.
They have a silver paint on the
face of the part.
The BF981s are similar parts to
BF961s.

SEE THE TEST RESULTS BELOW.
For starters.. the shipment of 6
BF961s came in an ordinary plastic
bag (left). They should have been
in a better Static Safe Bag.

Dual Gate Mosfets can get zapped
by static electricity.

See picture below of my hand
touching the grounded surface of
a piece of test equipment in my
radio/electronics lab.

I dont wear a wrist band (usually).
My basement shop has enough
residual humidity that static is not
much of a problem and I touch
ground frequently when handling
static sensitive devices.
Below .. periodic grounding by touching
grounded test equipment seems to be adequet
in my basement shop.
Above the tester is one I purchased from EBAY back a couple of years ago.
I really like the fact that the Chinese Vendors and Manufacturers have brought
us (here in North America) some real nifty test equipment like this. The prices
are very reasonable and I would not do without them now. They are
indespensible in my shop and I have other different types that test
capacitance, ESR in capacitors and Inductance and leakage in transistors ect.
I drew out the pin arrangements
for the BF961 and the BF981s.

The Drain is the long lead.

I took multiple measurements
moving the test leads around
to make sure that if there was an
error in my drawing.. I would still
catch the proper pins with my
tester.

The BF981s all consistantly tested
good.

I tested one lead on Drain, one on
Source and one on Gate.
I measured both Gates but had to
do them one at a time.

The BF981s measured good

The BF961s I measured over and
over again and I changed the
leads to every possible different
configuration. I also cleaned the
leads by scraping them with a knife
blade to make sure no oxide was
interfering with the test.
Still ..no luck.

I then took my V.O. M. meter and
tested the leads over and over
again and with different
combinations and polarities and
found that the BF961s gave no
readings at all on the ohms scale.

POSSIBLY .. there could be 4 leads
of the BF961 potted in plastic and
no internal connections at all !

I will be taking one apart to have a
look at whats inside !
If you have any older semiconductors (non China) I will buy them from you. Id like to stock only old known good
parts. My email address is earl@nettyelectronics.com and my link to this
email is CLICK HERE.. TNX 73 EARL
NOW TESTING THE BF961s. I tested each one
individually.

I tried every possible orientation of the test leads in
an attempt to get a reading other than the ones
shown here left and above and had no luck at all.

The BF961s are not good parts.


I have written the seller using the ebay messaging
system and have requested a refund on these parts.

I may end up taking them apart under high
magnification to see what actually the pin connections
(under the plastic) is !!

COULD THE TESTER ITSELF HAVE DAMAGED THE DUAL
GATE MOSFETS??

No would be my answer. I have (on other occasions)
tested dg mosfets and experimented with various
different configurations of the tester leads and have
never damaged a part this way.

All these (more modern design) DG mosfets have
diode protection built in and are fairly rugged but I
dont take chances. They could get damaged by a
static discharge so I ground myself periodically.
FOR A COMPARISON TEST .. I took a
drawer out of other Dual Gate Mosfets
that I have had here in my shop for many
years.


I put them on the tester and got good
results.

As you had discovered, bogus, fake, and otherwise counterfeit parts abound (I read your website)…. I needed 2 new finals,
2SC1971, a pair… Not to be found on RFPARTS.com.

So I went for an E-bay auction, 5 of them for $19USD. Too good to be true, and yes, it was indeed a lie. The parts I received test
on the Sencore tester were NOT “Base-Emitter-Collector”, but were “Base-Collector-Emitter”, and since most TO-220 parts
connect the center lead to the heat sink (often GROUNDED), a grounded collector was NOT going to work.

The lesser power driver, 2SC1970, is also “BCE”, so I tried the fakes as drivers.

Besides the Sencore showed their DC gain was crazy high (pulsed dc Beta of ~280+), are these a Fet or a Darlington??

Jon in California wrote the above to me (part of an email OCT 8- 2014)
Very interesting about the counterfeit components, and also a little
scary! These things are showing up in the civilian world, also. I may
be repeating myself when I tell you this, but one of our local club
members had a problem with fake parts not so long ago. Kris attended a
training course for aspiring hams that I helped provide back in 2010.
He passed his exams, and got an EI licence afterwards. He's a
qualified electronics engineer, but was a bit lacking in practical
experience, so when he built a little QRP SSB 20M transceiver from a
magazine design and was having difficulty he asked me to take a look.
The PA stage was designed around two common CB power transistors
(2SC1969, I think) but he was getting very low output. When I checked
his work, the output was low, with spurious. After a *lot* of head
scratching, we deduced that the PA transistors were fakes (an eBay
puchase). I guess that they were cheap switching transistors that had
been "re-badged".

Thanks to Gerry and Ei3 land ham who wrote this as part of an email to me June 2012

To Earl Andrews

Thanks for replying Earl.

Ya, china. They re-package anything and silkscreen a part # on it and send it out the door.

I once got a shipment from them. 10 2SC-1971’s. All three pins on the transistor (B.C.E) were a DEAD SHORT on every one of them. They
looked impressive enough.

I won’t buy from China on Ebay again. Ever.

If you do come across a good pair of 3133’s please let me know.
Ronnie



Ronnie S
VE3Nxx   -- Thanks to Ronnie who wrote me this email --- earlier
Hi Earl.

Do you have any 2SC-3133’s in stock?

And I am looking for Original Mitsubishi ones. I have tried 3 times to buy from China on E-bay, and they were all JUNK.
Let me know.
Thanks

Ronnie
This article is still being worked on and I will add more to it soon. (noted 19 JUNE 2015)

Besides these BF961 dg mosfets I also ordered 4 - LM317K steel Voltage Regulator ICs from the same
vendor.

I will be rigging up a test jig to test these under load in a power supply simulation project to see if these
voltage regulators work and can deliver the goods.  Stay tuned as more is comming down the pipe !


---- Do you have any good or bad experiences with Chinese Components?? I will publish both the good
and the bad.

See my other articles I have written concerning Dual Gate Mosfets and Transistors. Not everything
comming out of China is defective. There are some good things as well.

I wish that the Vendors would TEST -- some of their parts -- At least do a spot check periodically to verify
if the parts are good or not.

73 Earl VE3AB
I get quite a bit of correspondence by email here at Hamelectronicsmagazine.com and my
electronics components store: Netty Electronics (.com) and here's what some Electronics
Hobbyists are saying about Chinese Parts --->
Re: 2sk125 (exerpts from several emails I had with RON and NE0 radio callsign. regarding JFETs part nr 2SK125


ill send a mo, tnx fer cking them, i got ridden on ebay for ten fakes, but did get my money back. ron ne0x

I asked RON:   --->
Ok Ron. What were the problems with the ten you ordered? Were they just plain failures

or were they poor performers in the circuit? 73 earl ve3ab

 they were weak fakes and one was a plain old pnp. got mo here, will post tomorrow morn. ron

These BF981s with the Silver Face seem to be a
good batch of parts. I verified them and another
fellow I sold some to ..did tests on them and he
found them good. I also sent him some other BF981s
from another Chinese distributor and they did not
have the Silver finish.
These ones were all bad stock.
I sent him some good parts and after that
experience I now test all these types of parts. In
Fact.. I test anything I can test as much as possible
because of all the fake parts that are floating around.
       NOW TESTING THE BF961s and they all
tested as UNKNOWN COMPONENT.. in other
words they were not proper Dual Gate Mosfets.