Testing a fried Marantz SR50 - any tips?

Spasticteapot · 24th November 2006, 02:50 PM

I have a Marantz SR50 I got for free. It's toast, but I think I can fix it, and the output FETs are about 3$ each, anyway.

The diode rectifier bridge was blown (I replaced it with a RadioShack bridge), and while the control section seems OK, one of the channels (if used) instantly engages the protection relay.

Now, for a dumb question - what's the best way to test the individual transistors? Do you think an output transistor is blown (an easy fix), or one of the preamp transistors is blown (a hard fix)?

XEAGLEKEEPER · 24th November 2006, 05:00 PM

I would tend to be suspect of the output devices on the channel that triggers the protect circuit . Check out this site.for troubleshooting tips.
http://sound.westhost.com/troubleshooting.htm

Spasticteapot · 24th November 2006, 05:08 PM

Hmm...

I'll check the output MOSFETs. Any tips for doing so, or should I just blow 6$ and hope it works?

Finally, will my amp go "boom" if I remove the output transistors and try the headphone jack?

XEAGLEKEEPER · 24th November 2006, 05:16 PM

what is the part # on the fets? Chances are slim that you will do anymore damage with outputs removed provided you make sure that you don't leave any solder bridges ie. shorted traces after removal.

Spasticteapot · 24th November 2006, 05:28 PM

The numbers were:
A1263
C3180

Look like the A1263 is a Toshiba transistor - and hence, liable to be a fake.

XEAGLEKEEPER · 24th November 2006, 06:00 PM

Those are audio transistors not mosfets. If you have a dmm 1.)remove the transistors from the circuit . 2.)measure from base to emitter and from base to collector and from emitter to collector .3.) now reverse the test leads and make the same measurements they should measure similar to a diode. High resistance one way and low resistance with the leads reversed. If any combination reveils a zero ohms "bingo" LOL

Spasticteapot · 24th November 2006, 06:20 PM

Quote:

Originally posted by XEAGLEKEEPER
Those are audio transistors not mosfets. If you have a dmm 1.)remove the transistors from the circuit . 2.)measure from base to emitter and from base to collector and from emitter to collector .3.) now reverse the test leads and make the same measurements they should measure similar to a diode. High resistance one way and low resistance with the leads reversed. If any combination reveils a zero ohms "bingo" LOL

D'oh!

Will do. Anyone know where I can find replacements?

XEAGLEKEEPER · 24th November 2006, 06:23 PM

You asked .

XEAGLEKEEPER · 24th November 2006, 06:45 PM

http://www.newark.com/
Newark lists them bit doesn't have them in stock. Try a search on the net.

EchoWars · 25th November 2006, 10:14 AM

Digikey sells Toshiba 2SA1962 and 2SC5242 that will work fine. Overkill for your amp, but they'll be tougher to blow up.

24th November 2006, 02:50 PM	#1
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Testing a fried Marantz SR50 - any tips? I have a Marantz SR50 I got for free. It's toast, but I think I can fix it, and the output FETs are about 3$ each, anyway. The diode rectifier bridge was blown (I replaced it with a RadioShack bridge), and while the control section seems OK, one of the channels (if used) instantly engages the protection relay. Now, for a dumb question - what's the best way to test the individual transistors? Do you think an output transistor is blown (an easy fix), or one of the preamp transistors is blown (a hard fix)?

24th November 2006, 05:00 PM	#2
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	I would tend to be suspect of the output devices on the channel that triggers the protect circuit . Check out this site.for troubleshooting tips. http://sound.westhost.com/troubleshooting.htm __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*

24th November 2006, 05:16 PM	#4
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	what is the part # on the fets? Chances are slim that you will do anymore damage with outputs removed provided you make sure that you don't leave any solder bridges ie. shorted traces after removal. __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*

24th November 2006, 06:00 PM	#6
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	Those are audio transistors not mosfets. If you have a dmm 1.)remove the transistors from the circuit . 2.)measure from base to emitter and from base to collector and from emitter to collector .3.) now reverse the test leads and make the same measurements they should measure similar to a diode. High resistance one way and low resistance with the leads reversed. If any combination reveils a zero ohms "bingo" LOL __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*

24th November 2006, 06:23 PM	#8
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	You asked . __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*


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24th November 2006, 05:08 PM	#3
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Hmm... I'll check the output MOSFETs. Any tips for doing so, or should I just blow 6$ and hope it works? Finally, will my amp go "boom" if I remove the output transistors and try the headphone jack?

24th November 2006, 05:28 PM	#5
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	The numbers were: A1263 C3180 Look like the A1263 is a Toshiba transistor - and hence, liable to be a fake.

24th November 2006, 06:45 PM	#9
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	http://www.newark.com/ Newark lists them bit doesn't have them in stock. Try a search on the net. __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*

25th November 2006, 10:14 AM	#10
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	Digikey sells Toshiba 2SA1962 and 2SC5242 that will work fine. Overkill for your amp, but they'll be tougher to blow up.

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