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Transistor Substitutions

Could someone help me find replacements for these two pairs : 2SB1155/2SD1706 and 2SB985/2SD1347 ? (I have the schematic if needed)
They came out of a Nad 2400 power amp with one fried channel. I'm going to use the 2SA1493/2SC5200 as outputs.

Thanks
 
depaj said:
Could someone help me find replacements for these two pairs : 2SB1155/2SD1706 and 2SB985/2SD1347 ? (I have the schematic if needed)
They came out of a Nad 2400 power amp with one fried channel. I'm going to use the 2SA1493/2SC5200 as outputs.

Thanks
Click to expand...

Schematic always helps. The way a device is used in a circuit is always helpful in finding a suitable substitute.
 
The specs on the 2SB1155 are kinda extreme, so its application in the circuit is critical to finding a suitable replacement.
 
depaj said:
Here you go (although it might be better to get it directly on hifiengine for better quality)
View attachment 1223022 View attachment 1223023
Click to expand...

So, to search for a suitable replacement, you'll need to determine:

Highest voltage collector-to-emitter, collector-to-base, emitter-to-base, and highest current.

When I use just the specs from the datasheet:

180v
80v
7v
15A
TO-220,247,264-ish package

I don't find anything that Mouser currently carries. So, bringing down the specs to what is actually happening in-circuit is how you'll get specs or requirements for a more-successful search.
 
I measured voltage across the legs of the same transistors on the good channel and got collector to base voltage -30v without signal and -19v with signal at maximum ( no load connected). Same goes for collector to emitter voltage and maximum base to emitter seems to be around 200mV. From what I see on the schematic these would be part of the switching circuit between the low and high voltage power rails for the outputs so I guess it'll have to pass quite some current.
 
depaj said:
I measured voltage across the legs of the same transistors on the good channel and got collector to base voltage -30v without signal and -19v with signal at maximum ( no load connected). Same goes for collector to emitter voltage and maximum base to emitter seems to be around 200mV. From what I see on the schematic these would be part of the switching circuit between the low and high voltage power rails for the outputs so I guess it'll have to pass quite some current.
Click to expand...

And, without looking deeper at the schematic, it should be easy to say "Max voltage anywhere would be the total rail voltage" and "max current anywhere would be largest fuse rating". That's very rough guessing and I'm just a hobbyist, so that could be wrong.

What are your rails? What is the largest current value fuse?
 
Take a look at the TIP41CG/TIP42CG complementary pair and the MJE15032/MJE15033 pair. My non-expert guess is they are along the lines you should look at.
 
Hi guys! What is the substitution of the SL150 diode?? Couldn't find any information online. I removed it from pinch roller solenoid coil. The coil still working without this one!? Very strange... This is from Akai X-360D R to R.
Thanks!
 
ivo said:
Hi guys! What is the substitution of the SL150 diode?? Couldn't find any information online. I removed it from pinch roller solenoid coil. The coil still working without this one!? Very strange... This is from Akai X-360D R to R.
Thanks!
Click to expand...

Do you have a schematic for the Akai?
 
A leg broke on my 2SB536-L NEC brand transistor. Both NEC parts were mounted on a heatsink with a metal plate. The NEC seems to have 4 Pins
nec layout pin.jpg

Not sure if i put the replacements in the correct spot. They are KSA940 and KSC2073. Faults in the amplifer may not be related to them. Anyone used these parts to replace the NECs
 
Synchro-bias said:
A leg broke on my 2SB536-L NEC brand transistor. Both NEC parts were mounted on a heatsink with a metal plate. The NEC seems to have 4 Pins
View attachment 1254067

Not sure if i put the replacements in the correct spot. They are KSA940 and KSC2073. Faults in the amplifer may not be related to them. Anyone used these parts to replace the NECs
Click to expand...
Pin 2 (center pin) and Pin 4 (Tab) are the same. (collectors). There are some applications which have the center lead removed and the electrical connection is through the tab. (Older sansui amps - or the use a 2sb357 which is same transistor without pin 2).
All the subs listed have the same pattern (collector is both tab and center lead)
 
If you need a good replacement or help choosing a substitute for the 2SA726 PNP transistor, I've built a simple flowchart that takes you through the applicaiton needs your circuit has and leads you to the best modern equivalent device. The GIF below is a low res version of the PDF attached.

2SA726 practice.gif
 

Attachments

Question: it's possible to replace an (original) output transistor, fT of 15MHz, with another one of 20MHz? Big difference? Thanks.
 
Karl vd Berg said:
Question: it's possible to replace an (original) output transistor, fT of 15MHz, with another one of 20MHz? Big difference? Thanks.
Click to expand...
my favorite answer: It depends :D

One observation is that if I would have to replace one of the outputs with something other than original, I would replace all outputs with the same type of transistor...given that it is suited for that particular circuit.
 
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