I bought a broken Sansui B3000 yesterday. One channel of two was making a lot of noise. I switched output transistors, compared all components between left and right channel and all seemed fine. The problem could only be within one of the chips which I thought the driver was the guilty one. Since the chip pinout is practically in mirror I switched the IC 180 degrees and thereby switched internals of the chip. When plugging in the AC, hurray! The "broken" channel was no longer on the left output but on the right. Conclusion, half of the IC is broken.
Now, for the guys here, what is the best option to replace the SKT3152 III with? The exact same? The STK350 030/040/050 or a different one?
I would rather not change the rest of the circuit so a pinout-compatible version would be nice!
Ok! I ordered the STK3152 III and put it in. Success! The amp worked like it should. However; I was so happy I connected some speakers to it, thinking they were 8 ohm. After some time, poeff, some smoke from the right side of the amp and shortly after a fuse-flash. The speakers were 4 ohm's which made the amplifier deliver more amps than capable.(right?) I took out my trusty multimeter and started measuring the output transistors for defects.
On the left channel, the 2SC2921 seemed fried because of the fact, the Base-Emitter seemed shorted. No problem, I thought, because I wanted to replace the old ones anyway. I cut the Base-leg of the output tor in order to check for "extra damage". It then seemed that the driver transistor of the 2SC2921 was broken (too). The only text on the transistor says;
It is shorted between the Collector-Emitter.
After some googling I found this;
2SA1306A:NF/S-L, 180V, 1,5A, 20W, 100MHz
2SC3298A:NF/S-L, 180V, 1,5A, 20W, 100MHz
And this post on DIYaudio
For the 2SA1306A you could try MJE15031
The 2SC3298A will of course be replaced by the MJE15030
The MJE15032/33 combination is good also, even better. They have a higher voltage rating.
What should I do? Replace all power transistors and driver transistors or will I be digging my own grave and should I rather throw away the pcb and put in a modern LM4702 amp...
I found these on eBay. Will they be nice replacements for my original transistors? Since I can only find one threat on DIY audio about my transistors, I am not quite sure.
I would be highly cautious of those MJE devices from Hong Kong. There are massive problems with fake devices being peddled from Asia. It would suck to spend all the time, money, and effort only to have your unit fry again, and as Murphy's Law would have it, it would be far worse this time around : )
If possible, I would try to find a reputable mail-order house, or even see if you can order (purchase or samples) directly from www.onsemi.com They stock brand new OEM parts and have a great samples system. I don't know where they ship to, so you'll have to do some research.
But do you agree on the suggested replacements? They are better available!
My "local" electronics store has the following parts for reasonable? prices;
2SC4159; euro 1.15/pc (the replacement of the suggested 2SC3298)
2SA1606; euro 2.10/pc (its complementary)
Would this work?
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