Toshiba 2SA1924/2SC3425

[HighTec]

Hi guys,

I need these obsolete transistors. The problem is I never had them in my stock pile nor seen them in life. There are bunch of sellers ( mostly China ) on Ali and eBay who claims their transistors are genuine but the markings on them rings the bell. This is what Toshiba in their datasheet are showing how the markings should look like:

Does any good soul on this board have them or just make a screenshot so I can have at least some reference to start with ? Cheers.

For example some AliExpress transistors:

As you can see, the markings aren't consistent. Some of them don't even have the Toshiba logo. Yes, I know the rule: don't buy them from Ali and eBay.

 

[rayma]

There's a reason it's a rule.

 

[HighTec]

Hi, rayma. I know. It's actually lottery to find genuine stuff. Btw, Yamaha used them in their amps as pre-drivers. If I could just see them on the PCB.

 

[rayma]

Here's a 2005-8 Toshiba power transistor catalog with photos of their devices, maybe this will help.

 

[HighTec]

Thanks @rayma. Unfortunately the photos are poor quality. Looks like Toshiba took those photos with a potato. 📷

 

[as_audio]

You should obviously write how many you need.

 

[HighTec]

Sorry. At least 10 pairs.

 

[as_audio]

For a production quantity you should switch to other transistors if nobody supplies these.
However there is always a chance in this forum. Member RM has many semiconductors :
https://www.diyaudio.com/community/members/rm.29570/

 

[HighTec]

Thanks. I will contact RM if nobody comes up with a genuine photo or something.

 

[EUVL]

Perhaps TTA004/TTC004 or TTA006/TTC011 might also work for you ?
Toshiba current production.


Patrick

 

[HighTec]

TTA006/TTC011

Hi Patrick, thanks for your suggestion but I already have them in my stock. Here is why I'm looking for 2SA1924/2SC3425. Look at the schematic below. The power
supply voltage is +/- 150VDC.

 

[stocktrader200]

Ksc3503 and compliment both 300v
You may be stuck if you need 1A current.
MJE13007A is 400v 8A lower beta no pnp.

 

[wg_ski]

Yeah there is, MJE5852. But that pair is only good for ENHANCED VAS. Do not use by themselves or as predriver.

If you are stuck here, use KSC3503 and complement in the VAS/CCS position and MJE15034 and complement in predriver. The CCS is at 4 mA, and predriver doesn’t need much SOA above 150V. There was a fairly decent lowish gain but linear 400V 1A TO126 pair from Fairchild/ON, but are now NLA of course.

 

[HighTec]

Hi guys, thank you for your suggestions. The bill of material is almost complete except those predrivers/CCS transistors 2SA1924/2SC3425.
Since there are no proper substitutes, I'm stuck. KSC3503/KSA1381 are also in my stash but the hfe difference between them makes them
almost unusable. Same with 2SA1156/2SC2752. Btw, I'm using 2SA2223AY/2SC6145AY as output transistors instead of 2SA2151B/2SC6011B.

 

[HighTec]

Btw, some hfe readings:

KSA1156(Y) - 144
KSC2752(O) - 42

KSA1381(E) - 100
KSC3503(D) - 78

2SA1009A(L) - 52
2SC2333(K) - 90

 

[wg_ski]

If you HAVE A1156/C2752 go ahead and use them! Can’t get them anymore, but I bought 200 each some time ago for this very type of service. The VAS is single ended and cascoded. Hfe match between NPN and PNP doesn’t even matter. It’s also not a big deal in EF3’s either, but the MJE1503x are in general better parts for followers.

 

[HighTec]

@wg_ski,

so, you would use 2SA1156/2SC2752 in the cascode configuration ( Q209, Q211 ) despite the huge hfe differences ? Ok. What would you use
for Q219 and Q220 ?

Me and my OCD.

Edit: If you HAVE A1156/C2752

You mean the good old NEC Green/Black ? Unfortunately I don't have them. Only Fairchild KSA/KSC.

 

[wg_ski]

Q209 is only a CCS. It’s not amplifying an AC signal at its base. 211 is cascoded, so it’s dominated by what’s stuck in it’s emitter. 209 and 211 don’t even need to closely resemble matching. You just don’t want a lot of Cob in either - which is why I’d stick with the lower current TO-126 types. The CCS is running at 4 mA (0.6V/150R) so no need to go overboard.

My go-to for predrivers (Q219 and 220) are MJE15034/5 in high voltage EF3’s where an “output” transistor is used as the driver. The A1156/C2752 are likely fine - but I tend to reserve those for where they are NEEDED because I’ll likely be able to get more MJEs 10 years from now. Those high voltage TO-126’s will be gone gone gone.

 

[HighTec]

Ok boss !

 

[EUVL]

You can get both E grade here :
https://www.diyaudio.com/community/threads/fairchild-ksc3503-estu-ksa1381-estu.397239/post-7603101

Much better chance of closer hfe match



Patrick