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Transistor Substitutions

wyn palmer said:
Well, there you have it. It seems that the years spent in undergraduate and graduate school and in industry learning how transistors etc work and understanding how to design circuits were just a waste of time.
In all seriousness, if you think that you can simply replace devices with "generics" and guarantee correct operation to spec and reliable performance then you are utterly delusional, and if you think that you can just replace any opamp with a 741 and get identical or even, for that matter, acceptable, results across a multiplicity of performance dimensions then you are worse than delusional, you are, well, ridiculous.
Whatever your ears may or may not tell you, this is not good practice and should be actively discouraged, and the fact that your customers may find this acceptable just indicates that there are a great many uninformed, or indeed, misinformed, people out there who really ought to know better...
So yes, it is, and darn well should be, anathema.
I generally make a point of avoiding personal insults, even mild ones, so if I crossed the line, my apologies.
Click to expand...

No you did not cross the line. You made your point very well. The problem for me is satisfying customers quickly and cheaply. I live in a very depressed area. Their old stereos need to keep working. They or I cannot hear the difference in performance. Reliability is not a problem for me, I never hesitate to use overkill when replacing a transistor. If reliability were a problem, they would be right back on my doorstep. Yes I do set output voltages to zero and set current adjustments where they belong before they go out the door. I also blow out the dust unless it is from a smoker. It will not blow out, it becomes a sticky goo. And yes I do have some TO3 transistors that are rated for more voltage and current than the 3055 for those very high power receivers and power amps. Those too are very inexpensive. I have only had 3 of those really high power amps so far to repair. And yes I know, my repairs are not perfect. However, if the customer needs a distortion analyzer to know if his stereo is working properly he probably cannot hear the difference and that is why he needs the distortion analyzer. Just my take on repairing stereos in the backwoods. If I lived in NYC, I would be doing far more careful repairs and charging far more money. My biggest charge so far was 40 dollars for a right amplifier that went up in smoke. I even had to replace a smoked trim pot. I think we are talking from very different points of view. I admit, that for my own stereos, I will order and wait for very close replacements after using a generic temporarily. Not that I can hear the difference, I can't. I just want my own stereos to be perfect. BTW. I have mostly customers who have a total income of $2000 a month. Perfection in stereo repair is expensive. I have to ask. What would you do in my place when $40 is a high repair bill? Remember, saying you just would not repair those stereos is not acceptable to me or my customers. I am not trying to criticize you. I am trying to explain my situation. I am guessing you live where there is a far higher median income. So again, what would you do if you received a stereo with a smoked right channel that had all the transistors in the DC amp shorted and the trim pot smoked? And could you do it for $40?
 
Evening all,

I'm new and pretty green, with that said i'm looking to replace some output transistors in my Toshiba;

Old;
2SC793
2SA663

Replacements;
MJ21194G
MJ21193G

Unfortunately there are no visible specs on them :( There appears to be a lot of knowledgeable people on this thread - would i be fine to go ahead with what is on the list? A simple 'yes it will work' or 'no it will explode' will be fine as i will start a new thread to assist with the swap and not bog this thread down

Thanks in advance!
 
ChesterDraus said:
Evening all,

I'm new and pretty green, with that said i'm looking to replace some output transistors in my Toshiba;

Old;
2SC793
2SA663

Replacements;
MJ21194G
MJ21193G

Unfortunately there are no visible specs on them :( There appears to be a lot of knowledgeable people on this thread - would i be fine to go ahead with what is on the list? A simple 'yes it will work' or 'no it will explode' will be fine as i will start a new thread to assist with the swap and not bog this thread down

Thanks in advance!
Click to expand...
https://www.datasheetarchive.com/pd...52f50a9a978bc9d539e31e0a2e&type=M&term=2SC793
2N5758
http://www.svntc.com/TPDF/279.pdf
https://www.datasheetarchive.com/pd...2a57abecbb0e3490ce47861266&type=M&term=2Sa663
MJ15016
https://www.onsemi.com/pub/Collateral/2N3055A-D.PDF
Looking at the data sheets the two devices that you have selected look as if they would probably be OK, at least I can't see any reason why not. They're a bit of overkill in some areas, but there doesn't seem to be anything important that they don't meet or exceed the comparable specs of.
 
The replacements ought to be complementary, in other words designed by their manufacturer to work very well together, the MJ's suggested in post #223 are exactly that.
 
Thanks for you help - i really appreciate it.

I've ordered all the components i require, hopefully the old girl comes back to life. If you wish to see if i get the desired result feel free to check out my original thread;
'Toshiba SB-500 Power Supply Replacement?'

Again, thanks for all your help!
 
Hello again,

I'm working on a technics SU-V670 that doesn't come out of protection. There are some blown caps, some burnt resistors and some cracked transistors, looks like fun.
From the measurements I took in diode mode the output module (svi3205) is fine so I'm now looking for replacements.
I've got a pair of 2sa1123/2sc2631 that are used as pre-drivers in the voltage control amp that could be replaced with either ksa1381/ksc3503 or ksa1220/ksc2690 I think (maybe even ksa1142/ksc2682)
There also is one 2sc2631 that serves as a bias transistor for the outputs of the voltage control amp (mounted together on a little heat sink), not sure if I can use ksc3503 or ksc2690 here as well.
And then there is a limiter pair 2sa1309/2sc3311, no idea where to go with these.

Thank you in advance
 

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depaj said:
one 2sc2631 that serves as a bias transistor for the outputs of the voltage control amp (mounted together on a little heat sink), not sure if I can use ksc3503
Click to expand...
Yes, if there is nothing else in a TO-92 format and you are OK with using TO-126
2sc2240 would be a nice substitute if you had a way to get one.

depaj said:
And then there is a limiter pair 2sa1309/2sc3311, no idea where to go with these.
Click to expand...
what is wrong with KSC1815/KSA1015 ?
 
Does this mean the rest of my options are all good ?

rottalpha said:
Yes, if there is nothing else in a TO-92 format and you are OK with using TO-126
2sc2240 would be a nice substitute if you had a way to get one.
Click to expand...

Hmm, looks like there are a lot of fakes out there and I don't know any places that still sell the real deal without paying a fortune in shipping (like B&D).
I verified and to-126 fits nicely on the heat sink.

rottalpha said:
what is wrong with KSC1815/KSA1015 ?
Click to expand...

They look pretty close but are a lot slower, won't that be an issue ?
 
Hi all, I have some sa628a transistors to replace and the data sheet pinout doesn’t match the orientation of the ones installed in my receiver. Can anyone verify the pinout of this transistor?

Thanks
 
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