The ultimate DIY? A Stax SRM-T2!

[kevin gilmore]

mauser was legit.  went bankrupt more than 10 years ago.  they produced firearms. german manufacturer.

mouser is definitely legit. never got a fake part from them yet.

[simmconn]

On 7/12/2025 at 2:02 PM, micon21 said:

Your Majesty, is everything all right with your head? I show photo 1, where I demonstrate a tested sample, with a cool brand engraving. According to the measurements, hFE is much closer to the datasheet - hFE150. In photo 2, an awkward logo. hFE - as much as 341

You offered your opinion and analysis, I offered mine. Although we disagree, I hope we can respectfully disagree.

[judo]

On 7/12/2025 at 11:02 PM, micon21 said:

Your Majesty, is everything all right with your head? I show photo 1, where I demonstrate a tested sample, with a cool brand engraving. According to the measurements, hFE is much closer to the datasheet - hFE150. In photo 2, an awkward logo. hFE - as much as 341

 

Your style is not acceptable here

[micon21]

5 hours ago, simmconn said:

You offered your opinion and analysis, I offered mine. Although we disagree, I hope we can respectfully disagree.

sorry.

P.S.  I wrote my conclusion on 9360 in Mouser. I wonder what the answer will be.

Edited July 14 by micon21

[simmconn]

Okay. Please do report back when you hear from Mouser, then I’ll explain why I think hFE of 341 is more reasonable than 150 for an STN9360.

[kevin gilmore]

i just looked at what i had in stock.  F405 and F413.

both work fine. logo looks printed on. not etched and not stamped either.

[micon21]

15 hours ago, simmconn said:

Okay. Please do report back when you hear from Mouser, then I’ll explain why I think hFE of 341 is more reasonable than 150 for an STN9360.

Yes, I'm interested to know why the increase is twice as painful, maybe it's better?

[kevin gilmore]

Note, not my soldering job. battery in microscope dead

too much work to get the 1:1 lens out.

 

Edited July 14 by kevin gilmore

[kevin gilmore]

the 3rd one is the only one with the box after the cree label that matches parts i have.

my parts mostly have a w13814 date code

[simmconn]

23 minutes ago, micon21 said:

I will show three photos as a riddle. One copy from DigiKey/ two variants from China, and surprisingly, one of the Chinese ones is not a fake. Who can visually determine the fake?

How do you determine if a part is a fake? If a part with a poorly done or a suspiciously looking marking meets all the specifications of the genuine part that you can verify, would you still declare it a fake?

[GeorgeP]

Not sure why folks are continuing to indulge this idiot… maybe he’ll post some Gucci purses next. 

[micon21]

1 hour ago, GeorgeP said:

Not sure why folks are continuing to indulge this idiot… maybe he’ll post some Gucci purses next. 

 Please don't transfer your hobbies to me. I write only about radio components, that is, on topic. And you discuss about Gucci with women...

Edited July 14 by micon21

[kevin gilmore]

that box is 1000 pieces.  the mouser price for that is $283. i cannot imagine fakes for prices that low.

fake 2sj79 are going for about $15 each. which is why there are tons of fakes on ebay.

the typical hfe of 200 is the only spec on the datasheet.  no minimum or maximum hfe specified.

[kevin gilmore]

ST does not have a fab in china.  but they do have a back end site in china where the silicon is cut up and packaged. so the box says made in china.

Wolfspeed (formerly cree) also uses a back end site in china. which is why the c2m1000 is stamped china.

[micon21]

  when I bought in 2023 in Digi c2m1000170, they wrote that it was made in China. Now they don't have this model. I made a purchase on Aliexpress, alas, a fake arrived. I tried to make a purchase from another seller on Ali..., and to my surprise, transistors suitable for use arrived. I have already demonstrated photos of three purchases.

[simmconn]

34 minutes ago, micon21 said:

I already understood that 9360 were made in China, most likely the manufacturer did not think about a WORTHY logo of the STM company. I admit, I do not know, if the hFE measurements show not 120... 220. but show as much as 341, is this good? or as I assumed, this is not normal.

If I were to choose from a well executed raster image logo in the marking and a badly burned vector one, I’d opt for the latter in a heartbeat. I’ve explained the reason and would not repeat here. 
For the hFE, you need to know the Ic and Vce your testing was performed at, in order to make a meaningful comparison with the numbers in the datasheet. If you don’t know, measure them.

The datasheet says minimum hFE is 170 at 25 degree C, Ic=-1ma and Vce=-5V. From the chart you can see hFE goes slightly up from Ic=-1ma to -10ma and then to -20ma before it starts to drop after Ic=100ma (the red line). If your sample tests at hFE=150 between Ic=-1ma and -10ma, it’s below spec and would be a reject by the factory.

You can see the red line is well above 200 and approaching the 300 line, so 340 is not a surprise. +/-20% is considered normal variation.

Why would they specify min hFE at only 120 at Ic=-20ma? It could be a simple mistake, or indicating that the hFE could drop as early as Ic=-20ma, unlike what the typical curve suggests, which is a bad news for circuit designers (not applicable for our applications). Nevertheless, sandbagging would not get them into trouble anyways, if you know what I mean.

I could go on and on and brag about my affiliation with the semiconductor industry, but let’s keep the personal information out of this discussion. If you think my comments make sense, think about it. Otherwise, just take it with a grain of salt.

[micon21]

1 hour ago, simmconn said:

If I were to choose from a well executed raster image logo in the marking and a badly burned vector one, I’d opt for the latter in a heartbeat. I’ve explained the reason and would not repeat here. 
For the hFE, you need to know the Ic and Vce your testing was performed at, in order to make a meaningful comparison with the numbers in the datasheet. If you don’t know, measure them.

The datasheet says minimum hFE is 170 at 25 degree C, Ic=-1ma and Vce=-5V. From the chart you can see hFE goes slightly up from Ic=-1ma to -10ma and then to -20ma before it starts to drop after Ic=100ma (the red line). If your sample tests at hFE=150 between Ic=-1ma and -10ma, it’s below spec and would be a reject by the factory.

You can see the red line is well above 200 and approaching the 300 line, so 340 is not a surprise. +/-20% is considered normal variation.

Why would they specify min hFE at only 120 at Ic=-20ma? It could be a simple mistake, or indicating that the hFE could drop as early as Ic=-20ma, unlike what the typical curve suggests, which is a bad news for circuit designers (not applicable for our applications). Nevertheless, sandbagging would not get them into trouble anyways, if you know what I mean.

I could go on and on and brag about my affiliation with the semiconductor industry, but let’s keep the personal information out of this discussion. If you think my comments make sense, think about it. Otherwise, just take it with a grain of salt.

  In the batch that MOUSER sent me, the measurements were made at normal room temperature. One row of transistors had hFE 341, another - 315, the third - 295 and the fourth - 245. Which hFE would you use first?

Edited July 14 by micon21

[simmconn]

If you use them in a constant current source, the Vbe-Ic curve (figure 10) is probably more important than hFE. If you don’t have ways to measure, pick two that are closest in hFE for each channel and hopefully they come close in other parameters as well.
If you ask me, I always order at least 2x more than the BOM qty and match them on a curve tracer at or near the actual operating point. The bigger the pool, the more likely you’ll end up with well matched pairs.

[simmconn]

18 hours ago, micon21 said:

  when I bought in 2023 in Digi c2m1000170, they wrote that it was made in China. Now they don't have this model. I made a purchase on Aliexpress, alas, a fake arrived. I tried to make a purchase from another seller on Ali..., and to my surprise, transistors suitable for use arrived. I have already demonstrated photos of three purchases.

You haven’t answered my question how you determined that the part is a fake (other than from the appearance).

[micon21]

 I'm not in the mass production business, so I'm not going to BUY expensive devices, meters, analyzers, for basic hFE determination. Over the last ten years, I've built many different versions of electrostat amplifiers. Yes, not all of them worked. Yes, I didn't like all of them. For example, the mini T2 really disappointed me.

assembled version called carbon, I am happy for two years. But many music lovers always want something better. I hope  that T2 will outplay Carbon. 

Edited July 16 by micon21

[simmconn]

On 7/15/2025 at 2:52 PM, micon21 said:

 I showed three samples, one of the demonstrated ones, the device defines as IGBT.

I assumed that I was not the only one who encountered fakes...

Thanks. I guess nobody likes to receive fake parts. But if it’s a low-current, 1200V or better grade IGBT, its characteristics can come very close to the SiCFET we use in threshold voltage, transconductance and even input/output capacitance. It might actually work, at least in the GRHV. I’d be interested to try it out. Well, we should probably stop talking about SicFET or IGBTin this thread, as they are irrelevant to T2.

[micon21]

 When I was looking for 2SA1968, I also got PNP. I couldn't make a claim to the seller, because according to the Toshiba datasheet, there is such a version too. Model 1968, one for the whole world, n-p-n and p-n-p

Edited July 19 by micon21

[kevin gilmore]

2sa1968 is in fact a PNP 900v.  2sc1968 is a 500mhz rf amplifier.

Edited July 18 by kevin gilmore

[micon21]

On 7/19/2025 at 12:13 AM, kevin gilmore said:

2sa1968 is in fact a PNP 900v.  2sc1968 is a 500mhz rf amplifier.

sorry,  I have one 100% original and   2

fakes, many do not know who the original is.

 

Edited July 21 by micon21

[spritzer]

The original is on the right... the left one is clearly a fake