I was testing some JFET's using the test circuit from runoffgroove and discovered that an entire batch of 2N5458 transistors I recently ordered have strange Idss readings. Before I write and notify the company, I wanted to check to see if it is likely that something else might be up (like I'm doing it wrong).
I checked several other types of transistors; J201, 2N5457, MPF102, BF245A, and 2SK117GR's. These all were within the stated specs. For the 2N5458's, the Vp was within spec but the Idss was only about 0.1 to 0.15 mA where the spec sheet lists 2.0 to 9.0 mA.
Is it likely that these are either fakes or are just bad? Or, am I missing something in measuring these?
One other thing that makes me suspicious is that the face of the transistors is a slight bit rough. I haven't seen this before.
Thanks,
Rob
I built a madbean fatpants 2 and it sounds wicked, and i bought another batch of J201's, and built another couple for various friends, and they don't sound quite the same as mine.. i was wondering exactly the same as you, as the new batch of J201's are also slightly rough on the front..
i was planning to do some transistor testing/further investigation next weekend, i'll keep you updated as to what i find, and i'll keep an eye on here, as i'm interested to know the outcome..
George
The tolerances are pretty wide for most JFET production. I've certainly come across more than a handful that just won't bias in a dirt circuit. I check them all now before soldering anything in.
Thanks for the data points about the J201's. It's interesting that you saw the same thing on the face. The other thing I noticed was that the print wasn't quite as crisp as normal.
I understand that JET tolerances are pretty wide, but these are well outside the minimum (by about 20 times).
I didn't buy many of them, so no great loss. But, I think I'll contact the vendor and let them know and see what they think.