My Transistors, original or copy?

[jitter]

Originally Posted by PH104

I was shocked at the cost of the LT1084 on Digit-Key also and bought LM1084 instead. I didn't compare specs as I'm just using them for filament regs in a tube phono preamp (kevinkr's Muscovite).

I glanced over the datasheets, and it looks like they should be pretty much identical in performance. Why then the LT1084 should cost more than triple what the Texas Instruments' version costs is beyond me. Surely there's more to it than just production volumes?

[jitter]

Originally Posted by suzyj

Just goes to show that it’s not just hobbyists that get stung. This was a >$10K order by an organisation that should know better.

Right. The company I work for has made comparable silly choices. Sometimes forced by availability, sometimes because of price. That Xilinx Spartan from a few posts back? Yep, that is a good example. They were bought because of a lower price, and boy did that turn out to be more expensive in the long run.

Buying off eBay and aliexpress and the likes is asking for fakes. Hobbyists too can get the real parts from companies like Digikey, but they should be willing to pay the price that goes with them.

If something seems too good to be true, it usually is.

[Johnny Canuck]

Hey all, I just bought these jfets from a vendor and I have some suspicion that one pair may be counterfeits.
The upper pair in the attached picture looks like others that I have bought before - lettering appears etched in, and the "one" in 170 looks like "l".
The bottom pair have clearly been painted on (and badly at that).

IDSS measures okay for BL pairs (about 9.35mA for these pairs).
I tried looking for a schematic of a jig that would allow other measurements (pinch-off, etc) but found that some links in this thread redirect to bad places.

Hope that I can get some feedback on this before I go back to the vendor.

Thanks,

-Keith-

[WalterW]

That bottom pair is definitely fake. The upper pair looks OK. A bit strange that one vendor sells a good pair together with a bad pair.
They sell me only bad pairs

[WalterW]

Maybe this document from EUVL is helpful?

[Johnny Canuck]

Walter, thank you!

Originally Posted by WalterW

A bit strange that one vendor sells a good pair together with a bad pair.

Yes, the mixed pairs were puzzling to me as well, especially that these are from a well-known vendor in these forums.

Thank too for the link to EUVL's paper - I will do some tests to see just what we have here.

-Keith-

[thimios]

Originally Posted by Johnny Canuck

Walter, thank you!


Yes, the mixed pairs were puzzling to me as well, especially that these are from a well-known vendor in these forums.

Thank too for the link to EUVL's paper - I will do some tests to see just what we have here.

-Keith-

Why you don't say his name?

[Johnny Canuck]

Originally Posted by thimios

Why you don't say his name?

Hey Thimios, a natural linkage to be sure. For now, it is because the vendor should be made aware and given opportunity to respond.

-Keith-

[NicMac]

Originally Posted by WalterW

That bottom pair is definitely fake. The upper pair looks OK. A bit strange that one vendor sells a good pair together with a bad pair.
They sell me only bad pairs

I'm the vendor.
These FETs are perfectly genuine - all four of them.
You should know better than judging fakes by the type of marking.
Several different types of labelling were used by Toshiba over the years.

I will send you a pair of the "definitely fake" ones, if you promise to promptly post your finding here.

All my Jfets have been curve traced so I have nothing to fear.

Cheers,

Nic

[pdul]

If they all measures ok, it could be old and new production