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-   -   Burnt out transistors - replace with same or something better? Rotel RB-991 (http://www.diyaudio.com/forums/solid-state/223852-burnt-out-transistors-replace-same-something-better-rotel-rb-991-a.html)

inteificio 18th November 2012 03:59 PM

Burnt out transistors - replace with same or something better? Rotel RB-991
 
Hi,

One of the transistors in my Rotel RB-993 has shorted.

A toshiba 2sc5200

Easy to swap in a replacement.

However had a thought, it has been a while since this amp was designed, surely there must be something better out there now.

So what's your thoughts?

This amp is used to power the centre and surrounds in music/movie set up.

The front amps are Tag 8000p.

Current amp schematic attached:

https://docs.google.com/open?id=0B0W...0p0blFpaENQZjg

TANDBERGEREN 18th November 2012 05:01 PM

Why should there be any better transistors than the near legendary 2SC5200?

It's better to find out what made the short for You, than trying to replace with "a stronger device".
And why so? Well, neither of them will withstand a shortcirquit anyway.

And the 2SC5200 is still a very, very good transistor.

inteificio 18th November 2012 05:23 PM

I should have added I know very little about transistors. If this one is great, will stick with it.

Now I just need to find out what caused the issue.

Thanks

Mooly 18th November 2012 05:26 PM

I'll second TANDBERGEREN's reply.

Rebuild the faulty channel but use a bulb tester for powering up to save any mishaps. You need to be methodical and check for any damaged parts.

inteificio 18th November 2012 05:42 PM

Even with no load connected both board protection fuses go pop spectacularly.
Am very basic with electronics, but a shorted transistor is my guess.

Eventually I will remember to bring my multimeter home to give it a look over.

The main protection circuits do not detect a fault, it is just the 1 amp board.

jaycee 18th November 2012 06:50 PM

You cannot just drop in "better" transistors and get better performance. The circuit would have to be tailored to them, or problems such as oscillation will result.

There's nothing wrong with the 2SA1943/2SC5200. They are obsolete now, mainly due to rife copying and counterfeiting - Toshiba replaced them with TTA1943/TTC5200. There are some third party manufacturer clones made by Magnatec and Fairchild.

inteificio 18th November 2012 07:16 PM

Quote:

Originally Posted by jaycee (Post 3246567)
You cannot just drop in "better" transistors and get better performance. The circuit would have to be tailored to them, or problems such as oscillation will result.

Said I was basic =-)

jaycee 18th November 2012 10:17 PM

You say "both protection fuses blow". Which ones ? There are 2 pairs of fuses per channel.

inteificio 19th November 2012 08:03 AM

F301 and F302.

There are only two fuses I can find on each amplification board. There are other protection circuits on the shared, but these fuses are on the amp board itself.

Any tips?

inteificio 19th November 2012 08:22 AM

To save you looking around.

Page 1 bottom board.


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