I need help troubleshooting an class ab amp

I'm no expert on id'ing fake parts reliably but it might be worth you posting a clear close up picture of them. Some do stand out a mile as dodgy looking while others can be hard to tell. Worth a shot.

TIP3055's are widely available but I don't think the PNP TIP2955 is nowadays... but you could make a nice quasi complementary output stage with two modern genuine TIP3055's (the indestructible transistor as I was taught many many years ago... hmmm...)
 
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Has this question been asked? Where did he buy the transistors? I did the back of the napkin math, and he should be within the SOA. Maybe not with a ton of margin, but good enough. If the answer to my question is "AliExpress", then that's THE answer!
it was in shop near me. I didnt want to purchase them online because at the time i didnt want to wait for the delivery so i bough them in-person, but usually i have bough stuff like op amps and other transistors from them and didnt really experience problems with the components but i guess theres a first time for everything
 
Someone might spot something, you never know.
well i tried my best but im no professional 🙁
the desoldered one is the one that reently blew up and the normal one is the one i was planning to replace it with
badone.jpg
goodone.jpg
 
TIP2955 is available from ST, but their TIP3055/2955 are in TO-247. OnSemi only does the 3055 in that case. OnSemi makes MJE2955/3055 in TO-220. Are they an upgrade? Maybe. SOA at 40V is about the same (TIP3055 starts falling from 90W at 35V). Gain can be a little higher, but the spread from worst to best is larger.

If I were to use something “bigger” it would be the 2N6488 series or TIP35/6. Better gain linearity in either compared to TIP41/2.

I suspect fake here. That’s the new RoHS compatible package. That would be AFTER the OnSemi acquisition of Fairchild, so they would be labeled “ON”. And the “F” looks iffy to me too.
 
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Not important to mention here but as of now i'm just a semiconductor buyer (unfortunately), i done very limited number of diy projects( for friends & for myself) but with 100% success rate. I purchased some Onsemi MJE3055/2955 transistors too. Maybe oneday i'll do something with them, probably tda2030 with booster transistors 🙂
 
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and if its a fake transistor problemis is it worth it to get real tip41/42 or go for better transistors and if i go for better transistor which ones should i use(prefferably in the to-220 package)
If you can get guaranteed originals then it has to be worth a try. The ones in your picture may or may not be suspect. Is 'F' meant to be Fujitsu? There is doubt I suspect on these.

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it was in shop near me. I didnt want to purchase them online because at the time i didnt want to wait for the delivery so i bough them in-person, but usually i have bough stuff like op amps and other transistors from them and didnt really experience problems with the components but i guess theres a first time for everything
For semiconductors, i only trust Mouser and DigiKey these days. Period.

There are so many places in the supply chain where fakes can sneak in, so even well-meaning smaller vendors are likely to get fakes from time to time.
 
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You're right, it is, but are they genuine is the question. There are similar pictures on the web (do an image search for Fairchild TIP42) and this obviously stands out as fake. Also look at the spacing of the TIP4 1C

Get some others 🙂

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