sourcing small signal Transistors

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greenhorn

greenhorn

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I need a bunch of 2SC1312 or equivalent transistors for a tape preamp. I found that the 2SC1845 or KSC1845FTA are good replacements, and the one shop that had 2sc1845's had only three, and two of them dont have enough hfe (my DMM shows around 250, when they should have at least 600 - the third one has 1000+). I am guessing the high beta is needed

is there any other npn low noise high beta transistor (preferably with a BCE pin) i can use that's found locally?

If not, then If someone is buying parts from abroad, and can add this to their shopping list, I'd be glad to split shipping costs with them - can't really afford international shipping on my own.
 
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element 14 says NTE199/BC550C should be decent, but some digging on AK says they really don't work that well (folks who have tried swapping them have run into the same issues as I have) , and the KSC1845FTA is THE replacement. that's not there on element 14
 
I have some original NEC 2sc1845F with hfe in the range of 400..500, and I can match a few of them to within 1%. If you need higher hfe, you have to look specifically for 2sc1845E or D, which are harder to find, even on EBay. Except for a few applications, the hfe doesn't matter - however, the low noise and linearity of the 2sc1845 are unmatched by almost any other small-signal BJT. BC550 is ok, but doesn't match the 2sc1845 in Vceo, Va (Early Voltage), NF, hfe and hfe linearity with Ic. There are only a few NPNs which are lower noise than the 2sc1845, and almost all of them are discontinued and even harder to find. Even the Fairchild clone, the ksc1845, does not match the the NEC original on voltage noise.

PM me if the F-spec NEC devices will work in your application.
 
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This is the circuit. Right now, one channel does not work, and in that the second transistor is saturated, and the output of the first one is about .5V more than it should be, and its Vbe is .6V as opposed to the saturated one which has about .65

after some googling, i found and bought this
10pcs Panasonic 2SC1312 C1312 Amps Transistors to 92 | eBay
these are exactly the same devices i have right now. Hope they have enough gain!
 
I see a lot of electrolytics in that schematic - electrolytics tend to dry out over time, and in some cases the leakage current goes up significantly with age. Failed electrolytics are more common than failed transistors, so you may want to check all the electrolytics and replace them first before replacing the transistors.
 
the ebay plan was a bust. The devices they sent were 2SC1312R. and their gains are 150-250. Apparently I need 2SC1312G or H (higher gain)

Back to scratch. Any idea what to do ?
 
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Philips BC550c (China) if they're still available locally - these have a silver finish with black lettering - you should be able to select a fair proportion with Hfe > 500 in any lot. BC549c is an OK substitute if you can live with Vceo of 30V. Another alternative is the Toshiba 2sc1815-GR or -BL grade, hand-selected for Hfe > 400..500. The schematic shows a bypass cap rated at 16v only, so just about any NPN hi-beta should work there - Toshiba 2sc3112 should also work fine, and it has Hfe typically over 800..1000.

If you can't get hold of or use any of these, PM me for the 2sc1845F.
 
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greenhorn said:


This is the circuit. Right now, one channel does not work, and in that the second transistor is saturated, and the output of the first one is about .5V more than it should be, and its Vbe is .6V as opposed to the saturated one which has about .65

after some googling, i found and bought this
10pcs Panasonic 2SC1312 C1312 Amps Transistors to 92 | eBay
these are exactly the same devices i have right now. Hope they have enough gain!
Click to expand...

Dear sir,
by my experience, I dont think transies are the culprits. my idea is to replace all the electrolytes . (Keltron is a good advice. not because I'm a keralite anyway. they are direct replacement for Sprauge.) Then check all resistors with a DMM. If you are sure it is the transies, I think BC550/560 will work. fortunately, you have the other channel alive!
 
The resistors and continuity are fine - at least in the circuit. The 2SC1312's appear to be a known problem component - It figures in all the audiokarma replace lists. I Let me swap the capacitors - Anyway this is on hold for now since am working on something else. Anyway I use keltron too mostly, They are all thats available, and I'm a proud keralite, so it works out!
 
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Just checking if things have improved in 10 years. I ended up getting KSC1845FTA from abroad. Now i need it's complementary the KSC992FTA. any local options to source it?
 
greenhorn said:
Thank you! How much were the overhead costs on top of the parts(shipping, customs, other fees etc)
Click to expand...
KSA992FTA was also bought in that order, cost was 23.6 INR. No customs/other fees were in the invoice. Shipping costs were approximately 200 Rs
 
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