cheap but ubiquitous transistor tester mislabels TRIAC pins!

[cybermaus]

Hi all

I am sure many of us have one of these cheap ebay transistor testers. They are basically all clones from this original design. I bought mine already a few years back, but I recently accidentally bought two more (I kept ordering item A, they kept shipping me item B, so I ended up with 2 partially refunded totally unneeded testers)


Of which I gifted one to my nephew who was building his own lamp dimmer.  Turns out the tester is mislabeling the pins on TRIAC's
I tested TO92's small signal  BT131-600 and MAX97A6, both of which are supposed to have the gate in the middle, but the tester showed A1-A2-G.

I also tested medium signal BT136-600, which tested as, depending how it was connected to what tester: a N-MOSFET; a SCR/Thyristor; a common-cathode-dual-diode.
The only hint something was wrong was that both FET and diode showed a rather high Vt  of >4V. It seems testing for triacs is a bit tricky to get right.
(PS: diac testing shows "no device" but I guess the 30V threshold both ways makes that unavoidable. Like >9V zener diodes, I would not expect those ID'ed as well)

Anyway: out of interest, could other tester owners also check some triacs and see what you get.
Specifically, I am interested to know:

- If all cloned 2-line TXT models show the same erratic behavior on triacs.
- If the newer graphics models (which I do not have) also show this behavior.
- If the "brand" name devices (like Peak DCA55) deal better when identifying triacs.

Thanks

[Smith]

Well I only used the Peak DCA55, and really works like a charm. Its fast, and the PC software works really nice too. Never had any problem or incorrect reading ever. It recognised the strangest components we found, and we tried a lot.

[cybermaus]

Yes, but did you try any triacs?

Actually, shorty after posting above, I read the Peak DCA55's manual and it explains the reason triacs are difficult: The "high" trigger and hold currents. The Peak is only able to identify triacs with less then 5mA currents, as it does not allow higher currents to avoid damaging (other) components.

Makes sense to me.

Edit: The Peak DCA75 Pro goes up to 10mA. But they have a special triac tester SCR100 that goes up to 100mA
PS: I'd still like to know how those clone graphical ones are doing, if anyone has one.

Thanks

[GBowes]

All Thyristors can be a problem for this tester. The max gate hold current is 6ma. See the documentation for additional information.
If your Triacs are less than this (I am too lazy to get a data sheet) it might be possible for their identification and maybe the pin ids are incorrect in the software.
You could check this by testing a resistor between 1 and 2, then 2 and 3 then 1 and 3 and confirming which pins the software thinks are 1,2, 3.

You could get more useful help if you identified your tester and the software version. (edit: I see you did identify you tester -- I missed the link. Sorry) I have four testers with four different versions but collectively there are dozens or more variations of hardware and over 20 official versions of software plus countless other Chinese modified versions. With so many variables, even if others do or do not duplicate your problem, I am not sure you will have got closer to a solution.
Graham

[cybermaus]

Yes, I did check for simple overall pinswap, no such luck, the problem is only for triac.

I am not really looking to a solution as much as I am interested to know if other models (especially structural other models like the graphical ones) suffer the same.
Even more so since I learned that the (also graphical) Peak DCA75Pro has upped their test current to 10mA, I wonder if the clone ones followed suit.
So still interested if your models actually have the same fault, and if so, howmany out of all the ones you have.

Not that I need a new one. 9 out of 10 times all I do is doublecheck resistor and ceramic values. I know the colors from memory, but the bands are sometimes so vague.