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Old 23rd August 2005, 09:53 AM   #1
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Default :Help: Are these transistors interchangeable?

Just wondering if you guys think these two transistors are close enough to be compatible?

2SB1186A
http://pdf.alldatasheet.com/datashee.../2SB1186A.html

KTA1024
http://pdf.alldatasheet.com/datashee...C/KTA1024.html

They are part of an amplifier's driver circuit. It originally had the KTA1024, but it fried. And I have a few 2SB1186A's on hand.
I know the datasheet for the 1186A doesn't show pinout, but it's the same as the KTA1024.
I think they are close enough, but I'm no transistor expert and want a 2nd opinion.
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Old 23rd August 2005, 11:06 AM   #2
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Default Tarnationsauce, they are not perfectly compatible.

One of them have a very nice small capacitance...but a very small colector to emitter current.... this one is the KEC.

The Other one has enormous capacitance, and a very good colector to emitter current.

Removing the KEC and placing the other will be better than the oposite....this will depend of your application.

I do not think they are perfect substituted one for the other...only in very special cases of very low current applications.

Those transistors are not made to audio applications they are more adequated to power supply switching purposes.

Yes, they can work to audio, as one of them are already working, but some guys have the idea that the audio produced is not so good as can be when using standard BJTs, custom made for audio frequencies.

If you decide to replace, please inform the result.... as i have some doubts....lets listen other guys in advance.

nanabrother@yahoo.com

regards,

Carlos
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Old 23rd August 2005, 11:09 AM   #3
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Yeah, I notice 4-5pf vs 30pf is a pretty big difference.
This will be for low current application for voltage control.

I think I'm going to try it replacing the KTA1024 with th B1186A . I'll report back.
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Old 23rd August 2005, 11:17 AM   #4
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Default Yeah!...in your case, it will work!

But tell me some, after replacement.

There are always something to learn...will work...but i will be happy to listen if you could perceive some advantage or the opposite.

regards,

Carlos
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Old 23rd August 2005, 11:19 PM   #5
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I replaced the transistor and the amplifier plays audio, but buzzes then goes into protection mode.
So I either have something else wrong. Or something about this transistor makes it incompatible.
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Old 24th August 2005, 12:36 AM   #6
anatech is offline anatech  Canada
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Check to see if you are now a radio station.

-Chris
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Old 24th August 2005, 01:14 AM   #7
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Quote:
Originally posted by anatech
Check to see if you are now a radio station.

-Chris
I forgot to mention that this is a high power audio amplifier.
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Old 24th August 2005, 01:33 AM   #8
anatech is offline anatech  Canada
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RF. You have an AF amp. Is it now an RF amp also? (Oscillation)
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Old 24th August 2005, 02:54 AM   #9
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A better choice would be a 2SA1124

get the data sheet through Digi-key and compare.

ft is higher but the rest is very similar
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Old 24th August 2005, 06:49 AM   #10
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Quote:
Originally posted by anatech
RF. You have an AF amp. Is it now an RF amp also? (Oscillation)
-Chris
Lol, sorry I misunderstood your question.
Actually, yes! Just about .5 seconds before it shuts down it oscillates. It sounds like it's about 60Hz. I have a scope at my disposal, should I take a reading of it? Is there a way to stop it? And how did you know that was a possibility? Was it the high Cob of the b1186a?
also, is your avatar a quote form That 70's Show?

Quote:
Originally posted by DUG
A better choice would be a 2SA1124

get the data sheet through Digi-key and compare.

ft is higher but the rest is very similar
Yeah that does seem like a good replacement, except the hFE is quite a bit higher too. Doesn't that mean it has more gain? A higher ft shouldn't effect anything I don't think.

Thanks, everybody for your help so far.
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