Hello!
What do you think about this MOSFET I think this is counterfeit? I have never seen this MOSFET in this case. Its looks like professional but I think it doesn't mean anything. If I search in google 2SK1058 I found only in other case. .
I try to measure the Vgs/Id characteristic but it wasn't successful and at moment its behavior is like should be shortstop between Drain-Source legs. Presumably its dead.
Earlier I measured IRFP240 and it worked very well. Of course I used same measure circuit but the components have different values because IRFP has higher Vgs value.
Does somebody have measure circuit for 2SK1058?
It would be very important because I have started to build hybrid amplifier and I would like use 4 pieces of 2SK1058.
I'm going to order matched them for safety sake from Borbely Audio. I would like to draw characteristic curve for every MOSFETs.
Gyuri (George)
What do you think about this MOSFET I think this is counterfeit? I have never seen this MOSFET in this case. Its looks like professional but I think it doesn't mean anything. If I search in google 2SK1058 I found only in other case. .
I try to measure the Vgs/Id characteristic but it wasn't successful and at moment its behavior is like should be shortstop between Drain-Source legs. Presumably its dead.
Earlier I measured IRFP240 and it worked very well. Of course I used same measure circuit but the components have different values because IRFP has higher Vgs value.
Does somebody have measure circuit for 2SK1058?
It would be very important because I have started to build hybrid amplifier and I would like use 4 pieces of 2SK1058.
I'm going to order matched them for safety sake from Borbely Audio. I would like to draw characteristic curve for every MOSFETs.
Gyuri (George)
Attachments
There are counterfeit 2SA1943s (and presumably 2SC5200s) floating around in Bangalore - if the plastic encapsulation is green in colour, it is definitely a fake. Even those in black encapsulation are suspect - memorize the pictures of the good ones at the beginning of the thread to distinguish the originals from the fakes. Apart from the heatsink outline (if the straight edges are not exactly straight, but rough or jagged, it's a fake), look at the plastic moulding - if there are pieces of plastic chad hanging off the seams, it's a fake. The genuine Toshiba has smooth moulding edges and the plastic at the seams of the two halves is smooth. OTOH, the surface with legend on it is matt, and the legend is harder to read on the genuine than the counterfeit.
The good news - I have located genuine ones priced at around Rs.100 (~$2.50) a pair, while the fakes are priced at Rs.120-Rs.150 a pair - go figure the economics, it beats me. Anyway, I'm tempted to stock up and offer them to forum members in Bangalore if there's sufficient interest.
The good news - I have located genuine ones priced at around Rs.100 (~$2.50) a pair, while the fakes are priced at Rs.120-Rs.150 a pair - go figure the economics, it beats me. Anyway, I'm tempted to stock up and offer them to forum members in Bangalore if there's sufficient interest.
Hello Linuxguru,
I had posted earlier in this thread about having purchased these transistor in Bangalore ( from Darshan Electronics on SP road ) for Rs90 a pair.
While the parts seem genuine (I even cracked one open just to check ) , I found quite a difference in the hFE values between the PNP and NPN devices at Ic = 1A.
Makes it a pain to get a decently matched pair.
None of the parts failed, but then I am yet to run my amp at its rated supply. I have a lousy PSU right now.
Cheers,
Santhosh
I had posted earlier in this thread about having purchased these transistor in Bangalore ( from Darshan Electronics on SP road ) for Rs90 a pair.
While the parts seem genuine (I even cracked one open just to check ) , I found quite a difference in the hFE values between the PNP and NPN devices at Ic = 1A.
Makes it a pain to get a decently matched pair.None of the parts failed, but then I am yet to run my amp at its rated supply. I have a lousy PSU right now.
Cheers,
Santhosh
Chetan Electronics also stocks authentic ones from original Toshiba bulk packs, though it seems to be out of stock presently. He also has TO-3 MJ21193/21194 and many other ON Semi power BJTs, but I haven't inspected them closely enough to tell if they're authentic. It's probably impossible to tell without a dissection.
Regarding the mismatched hFE, it's probably not a big issue for class-B/AB emitter-follower output stages. As long as the driver stage is capable of supplying the required base current, things will be ok, and the mismatch will be corrected by negative FB.
I now have 2 pairs of pulled 2sc5198/2sa1941 (lower spec, smaller-die versions of the 2sc5200/2sa1943) in TO3P packages, which are fairly nice replacements for legacy TO-3 transistors (2N3055/MJ2955 etc.). I'm trying to make up my mind on whether to experiment with them to build a small, high-end amp like the Leach or similar, or simply buy a used vintage Japanese discrete power amp from Chennai and upgrade the op-amps, semis and electrolytics. There are plenty of Sansuis and Onkyos floating around, and a few Nakamichi/Pass Stasis as well.
BTW, there's an inexpensive Chinese car power amp, 2 channels, which can probably do about 35W-40W/channel into 8 ohms that's available in S.P.Road. It's called the Bob BE-1202 or similar. I bought one, took it apart, and found that it's a discrete bipolar power amp, driven by an op-amp pre- and active-filter stage. A few simple upgrades (mainly power semis and caps) will allow it to give many years of excellent service. Not too bad for Rs.2200/- (~$55).
Regarding the mismatched hFE, it's probably not a big issue for class-B/AB emitter-follower output stages. As long as the driver stage is capable of supplying the required base current, things will be ok, and the mismatch will be corrected by negative FB.
I now have 2 pairs of pulled 2sc5198/2sa1941 (lower spec, smaller-die versions of the 2sc5200/2sa1943) in TO3P packages, which are fairly nice replacements for legacy TO-3 transistors (2N3055/MJ2955 etc.). I'm trying to make up my mind on whether to experiment with them to build a small, high-end amp like the Leach or similar, or simply buy a used vintage Japanese discrete power amp from Chennai and upgrade the op-amps, semis and electrolytics. There are plenty of Sansuis and Onkyos floating around, and a few Nakamichi/Pass Stasis as well.
BTW, there's an inexpensive Chinese car power amp, 2 channels, which can probably do about 35W-40W/channel into 8 ohms that's available in S.P.Road. It's called the Bob BE-1202 or similar. I bought one, took it apart, and found that it's a discrete bipolar power amp, driven by an op-amp pre- and active-filter stage. A few simple upgrades (mainly power semis and caps) will allow it to give many years of excellent service. Not too bad for Rs.2200/- (~$55).
2SC2705-Y and 2SA1145-Y
Hi,
I acquired some of those some years ago and bought lots more just a couple of days ago. The problem is, they don't look the same. I'm quite confident the ones I bought some years ago are originals. Now I want to find out whether Toshiba changed their package or whether I was sold counterfeits... Can you help?
First picture shows the transistors which I believe are genuine.
Hi,
I acquired some of those some years ago and bought lots more just a couple of days ago. The problem is, they don't look the same. I'm quite confident the ones I bought some years ago are originals. Now I want to find out whether Toshiba changed their package or whether I was sold counterfeits... Can you help?
First picture shows the transistors which I believe are genuine.
Attachments
