MY LATEST PURCHASE FROM EBAY.. 30 BF981s FROM UT Source (a company that I like dealing
with from China).. these parts turned out to be duds.

www.earlandrews.com -- www.ham
electronicsmagazine.com (mirror sites) by Earl Andrews

(this article rewritten 28 February 2014- Now using a more sophisticated tester I just received in mail)
THESE ARE THE GOOD BF981s. I still have about 15 from previous buys. I have tested
12 so far today (25 Feb 2014) and none tested bad. They have a distinctive silver face
on one side with the part number and PH (which I think stands for Phillips)

TO TEST DUAL GATE MOSFETS with the simple testers I have in my shop..I jumper
connect the gates together with a jumper wire. THIS SEEMS TO WORK FINE for
testing and I think it would work ok in an electronic circuit as well. My testers only
have 3 leads..one for gate, 1 for Drain and 1 for Source.
This is not a commercial magazine. I just impartially report what I find out! I test components as I collect them and I sell some here and there to
pay for the hobby. Anyways.. I have been buying parts from UT SOURCE. They are a bit more expensive and their shipping is not free shipping
like some of the big Chinese sellers on ebay..$4 shipping..but you can order a big order of parts to spread the shipping out ..like this order of
30. Shipping per part comes to roughly 13 cents per part. These parts were only $1.00 each-- A BARGAIN??? - NOT AS IT TURNS OUT! KEEP
READING!
Here is a close up picture of the ones that tested as UNKNOWN COMPONENT or
DAMAGED COMPONENT ..in my test station set up. Some of the TEST READINGS from
my new tester are in chinese lettering so I dont understand that part.
The items are still up for sale on ebay today 28-Feb 2014.
Above: Screen Snapshot from "My Ebay" -

Below: the email that prompted me to test these dual gate mosfets - recently bought on ebay..as per the
screen snapshot above.
Hi Earl,

This is V from SOMEWHERE IN : , Nova Scotia. Today I received my order. Thank you for prompt shipment.

All parts are good, except BF981 (5 pcs.).  I dealt with them on a piece of copper foil and tested them in my MOSFET tester.  Three
transistors are dead. Two are faulty: drain current does not change when gate 1 voltage changes.

Actually they are from a different batch compared to those you sent me before. Those (all working) were with marking printed on the silver
face and had a flat black back. These are all black and the back has a depression. I’ll send them back to you tomorrow so you can test
them if you want.


Do you still have those silver-face BF981?

Regards,


V---     ( NAME IDENTITY PROTECTED).

my note: ABOVE THE EMAIL THAT started me to investigate these parts. --- Moral of the story.. Keep a tester on the bench
and test your parts if you can! - Thats what I do..

ALSO.. I GUARANTEE MY PARTS. I am a little one man basement hobby shop. When I sell parts ..and if they dont work..I
replace them!

FROM NOW ON.. IM GOING TO BE TESTING MORE OF MY PARTS AND NOT TAKING ANYTHING FOR GRANTED --- I dont make
many mistakes..but no one is perfect!
UPDATE: 27 FEB 2014- Now using my new tester (YIWANJIA) that I received from an
ebay vendor from China. It was advertised as a "more powerful"tester. It is more
powerful than the older simpler tester I was using previously. SO.. I rewrote this
article today - 28 February 2014- Results were: all these parts (the black faced
parts (not the silver faced parts) are all bad. All 30 that I ordered from UT Source
were defective in one way or another.

THIS BEING SAID: UT Source has been communicating with me via email and they
are taking the parts back and refunding my money for the purchase plus the cost I
have incurred sending in the mail back to them (about $5.00 or so) US DOLLARS for
this purchase.
So I am still happy with UT Source and I am working with them to
help them improve their business.
Above and below: the BF981 defective parts. Just plain black with lettering on it. -- NOTE:
my shop is down the basement and there is enough residual dampness in the basement
that I do not work with an ESD mat on the bench. I ground myself periodically by touching
a metal piece of test equipment periodically ..when I work with small electronic parts, in
particular - anything with MOS technology. I have done this so often now and never had
any problems with parts being damaged by static electricity.
THE DRAIN IS THE LONG LEAD. The source lead has a distinctive little tab sticking out and
both gates are plain leads.
During testing: this message was a common message on the tester when testing
these defective dg mosfets. Not sure what this means because I dont read
chinese. Perhaps someone from UT Source..(they have been directed to this web
page) or perhaps someone else will clue me in!
At least on one occasion..this was the result screen from testing the defective
BF981s! (above)
BELOW RIGHT .. EVERY SINGLE TIME I TESTED ONE OF THE SILVER FACED BF981s
- I got this symbol (note that the two gates in all these tests were tied together to
simulate just one GATE). This looks like the proper symbol for this device. By
comparison..the bad dg mos fets bf981s had various other screen display results
and non tested (I tested about 15 or so of the entire batch of 30) NONE OF THE BAD
DEVICES GAVE ME THIS display screen below. So..its is pretty conclusive that the
whole batch of 30 I received from UT Source were defective in one way or another.
ABOVE: THe resulting display above occurred a number of times when testing the bad
BF981s. Looks to me like a normal JFET of some sort..maybe something like an MPF102--
(who knows!).

I think it is IMPORTANT during the manufacturing process ..to have some quality control!
Where was the Quality Control when these devices were being manufactured???

Could be a number of different situations: Could be bad parts that were smuggled out of the
plant and sold as good merchandise! --

China is certainly manufacturing some real good items and at a reasonable cost that a person
like me (retired on a fixed income now) can afford some nifty test equipment!

This YIWANJIA tester here..is real nifty. I like it alot. I just got it in the mail and it was real easy
to use.  

So..my advice to Chinese distributors is: SPOT CHECK SOME OF THESE ITEMS YOU ARE
PUTTING UP FOR SALE! -

I bought 30 of these because the price was only $1 each (US dollars) so UT Source probably
got them at a real good price as well!

Sometimes a good price means poor quality! So do some checking on these low cost items
you are selling. - IF THEY ARE DEFECTIVE.. DON'T SELL THEM.

ACTUALLY..THEY SHOULD BE DESTROYED!!!!!
Unfortunately..I sold 5 of these bad devices..presumming that the UT Source parts
were pretty good. - I have since sent this fellow 6 of the good dg mosfets (1 freebie)
Today - 28 February 2014-- UT Source has agreed to take back the parts and refund me the price and my cost to send them back.

MEANWHILE.. I went out and bought 30 more DG mosfets -- BF981 to stock up again (I SELL TESTED PARTS AS A HOBBY OF MINE).
I also research and collect electronic parts.

Anyways..these cost a little more but they are guaranteed for 90 days. I will be testing this new batch when they come in!


73 Earl VE3AB -- My H
OME PAGE IS HERE..--- MY SUPERBIG PARTS LIST (I SELL PARTS TO HOBBYISTS AND TINKERERS ECT IS HERE)