2SC1345(E) replacement doubts

Sergimm

Sergimm

Active Member
I am following the routine replacement of old 2SC1345 transistors with KSC1845FTA in the control board of a Kenwood KA-5500, but I can’t find the data sheet for the E model of the 1345. They are the ones with the “outhouse” shape, and they have blackened legs up to the transistor itself, so they have to go. I am just doubting now if the KSC1845FTA are the ideal replacement.

The (attached) specs seem to be similar enough, but I’m no expert on transistor matching by any means. Is it still a good replacement?
 

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Sergimm said:
I am following the routine replacement of old 2SC1345 transistors with KSC1845FTA in the control board of a Kenwood KA-5500, but I can’t find the data sheet for the E model of the 1345. They are the ones with the “outhouse” shape, and they have blackened legs up to the transistor itself, so they have to go. I am just doubting now if the KSC1845FTA are the ideal replacement.

The (attached) specs seem to be similar enough, but I’m no expert on transistor matching by any means. Is it still a good replacement?
Click to expand...
control board as in? speaker delay, DC protection, thermal protection?
what current is the transistor seeing? schematic?
 
It isn't a perfect replacement, but its close enough for most applications. The only other substitute part readily available is the BC550C, but you'd need to twist the legs to match the pinout.
 
rottalpha said:
control board as in? speaker delay, DC protection, thermal protection?
what current is the transistor seeing? schematic?
Click to expand...
I'm only seeing 2 in the unit Qi1 and Qi2.. TONE Control final output. ie.signal path
 
Sergimm said:
I am just doubting now if the KSC1845FTA are the ideal replacement.
Click to expand...
So 1845 would be a candidate if you want to stick with low noise, same pinout, but the BC550 is actually a better match with the original, if you can put up with the leg twisting.
 
avionic said:
You didn't look very hard.. Took me less than 20 sec.
E = Hfe rank 400-800
https://www.datasheetarchive.com/pd...3881c19f5750793cf7ef9f228&type=M&term=2SC1345
Click to expand...

Ah, that's embarrassing. I actually kept finding this one but ignored it because both the shape and the pinout were different. I missed the table with the different models...

But then if nominal hfe is 400-800, does it mean that the existing ones in the board are degraded? The meter gives me hFE=155 in one and hFE=99 in the other. That seems quite low compared with the spec.
 
rottalpha said:
So 1845 would be a candidate if you want to stick with low noise, same pinout, but the BC550 is actually a better match with the original, if you can put up with the leg twisting.
Click to expand...
Interesting, I see BC550 is also a low-noise transistor. Is it worth the trouble, in your opinion? I'd have to order it, and I'm not terribly excited about the leg-twisting. If there's going to be no real difference with 1845 I'd rather keep that.
 
Sergimm said:
Interesting, I see BC550 is also a low-noise transistor. Is it worth the trouble, in your opinion? I'd have to order it, and I'm not terribly excited about the leg-twisting. If there's going to be no real difference with 1845 I'd rather keep that.
Click to expand...
well, what is the circuit current? In the amp section above, Kenny gives you all voltage annotations at the transistors pins. Do you have that view for the tone control section ?
It looks like +B is 25v / 12mA for your circuit. In that case Q1 circuit current is 12ma and the emitter pin sees just over 19v so a 50mA / 120v (Vce) transistor should be OK.
The only thing I see different is the fT. The 1845 is about a third of the original and that of the BC550.
 
The BC550C and 2SC1345E have better Vce saturation properties than the KSC1845F and as rottalpha noted, somewhat faster. That probably doesn't matter here. The 2SC1345E on paper has better low frequency noise specs than the other 2, but that doesn't matter here. I'd put the KSC1845FTA in and be done with it.
 
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