help blown yamaha amp

namcir · 24th November 2005, 06:34 PM

hi to all
i have been around a lot but this is my first post.
i just blown my yamaha amp buy adjusting its bias almost to the max. fortunately nothing in the output devices failed ( i think so) but the power supply devices blew up (swithch mode) leaving black smoke on its surroundings. do anybody have the same expereince? what did i do wrong?

help

MikeB · 24th November 2005, 06:42 PM

Possibly you overheated your outputdevices, bias to max might have been several amperes. Solder out one of the outputdevices and measure it. They are very likely to be shorted. In this case i would consider this amp a complete loss...

sorry,
Mike

namcir · 25th November 2005, 07:43 PM

thanks Mikeb for your reply:
yes it is a big loss for me maybe i would be careful next time i tinker to my equipment. now i need a service manual to be able to service it properly could anybody help me acquire one? the model is yamaha pro-audio P7000s. please help

nikwal · 25th November 2005, 08:38 PM

My experiences with switch mode psu's says that if one component there fails MANY others probably will..
I've looked at a couple of yamaha schematics on pdf and they are'nt too complicated in the power amp , You could at least try to measure the transistors with mutimeter diode function, dont rely on it though! transistors may be "half" broken..

anatech · 25th November 2005, 09:05 PM

Hi RICMAN,
Yamaha normally has good protection networks and may be in shutdown mode. With any luck, you just killed the outputs, maybe drivers and more.

In general, leave bias settings at factory default. This is more true with pro amps that have to be reliable.

-Chris

anatech · 25th November 2005, 09:08 PM

Hi RICMAN,
Rereading, I see you have let the really expensive smoke out of the box. Could be fun, but not impossible to fix.

To repair switching supplies, you need a way to vari the power so it doesn't just go bang if there is another fault. Another bipolar variable power supply may allow you to troubleshoot and fix the output stage.

Wishing you luck with this.

-Chris

destroyer X · 26th November 2005, 02:11 PM

Because of switching power supply and over bias....extremelly overbiased...will be lucky to find fusistors burned.

I think this amplifier soul is already in the skies.

Sorry....bad luck for you....a hard to work to fix...and no guaranteed that the cost of parts are adequated to the equipment used market value....maybe parts turn expensive to put it in order again....those output transistors are highly selected...they are very well matched...hard to find matched units to substitute them....factory use to order sequence of transistors from the same silicon wafle...almost identical units.

regards,

Carlos

adason · 26th November 2005, 02:21 PM

hi ricman

i once had similar problem with an old akai power amp
it had switching supply to make it light and sleak, which died after a while
i replaced it with outside trafo/rectifiers and caps
sounds great till now

i would not waste time with switching power supply
get the external and start replacing blown parts in the amp
don't give up

good luck
e

destroyer X · 26th November 2005, 05:25 PM

Will be more easy to fix...as two problems at same time is complicated...to fix the amplifier you need to trust in your supply.

That's a very good idea.....remove supply, substitute by another you prepare, needing more voltages will be easy to prepare with zener and transistors...just tell me the voltage you have and the voltages you need and i can do it for you...and them go to fix the amplifier.

Have some schematic?.....without it may be more difficult...but not impossible.... remove transistors, one by one, in the power unit, and check them...in advance...disconnect all supply wiring...cut keeping color code into the amplifier board...and measure from plus to ground and from negative to ground searching for short circuits....but remove supply.... as the short can be produce be the supply....well...working hard...you may ressurect it.

regards,

Carlos

adason · 26th November 2005, 08:38 PM

here is the pic of that akai amp
it was part of very fancy mini hifi
amp was the best part of it
preamp sucked, tuner and deck was quite good

it has two huge hybrid power packs inside and with new power supply outside (capacitors are inside the amp) can deliver clean 75 watts

24th November 2005, 06:34 PM	#1
namcir diyAudio Member Join Date: Jul 2005 Location: mid_east	help blown yamaha amp hi to all i have been around a lot but this is my first post. i just blown my yamaha amp buy adjusting its bias almost to the max. fortunately nothing in the output devices failed ( i think so) but the power supply devices blew up (swithch mode) leaving black smoke on its surroundings. do anybody have the same expereince? what did i do wrong? help

26th November 2005, 02:11 PM	#7
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	The work to do, i am afraid, is more ressurection than repair Because of switching power supply and over bias....extremelly overbiased...will be lucky to find fusistors burned. I think this amplifier soul is already in the skies. Sorry....bad luck for you....a hard to work to fix...and no guaranteed that the cost of parts are adequated to the equipment used market value....maybe parts turn expensive to put it in order again....those output transistors are highly selected...they are very well matched...hard to find matched units to substitute them....factory use to order sequence of transistors from the same silicon wafle...almost identical units. regards, Carlos __________________ Sons visiting uncle charlie; http://www.youtube.com/watch?feature...&v=5T76qsvZrdw; http://www.youtube.com/watch?v=Hb_wolQGU5Y

26th November 2005, 05:25 PM	#9
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	Good idea...removing switching supply and installing a standard supply Will be more easy to fix...as two problems at same time is complicated...to fix the amplifier you need to trust in your supply. That's a very good idea.....remove supply, substitute by another you prepare, needing more voltages will be easy to prepare with zener and transistors...just tell me the voltage you have and the voltages you need and i can do it for you...and them go to fix the amplifier. Have some schematic?.....without it may be more difficult...but not impossible.... remove transistors, one by one, in the power unit, and check them...in advance...disconnect all supply wiring...cut keeping color code into the amplifier board...and measure from plus to ground and from negative to ground searching for short circuits....but remove supply.... as the short can be produce be the supply....well...working hard...you may ressurect it. regards, Carlos __________________ Sons visiting uncle charlie; http://www.youtube.com/watch?feature...&v=5T76qsvZrdw; http://www.youtube.com/watch?v=Hb_wolQGU5Y

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Yamaha M-45 Blown Output Transistors	gni	Solid State	35	29th July 2008 09:47 PM
Blown sub?	dafish48	Car Audio	1	13th October 2006 06:21 AM
mtx blown please help	ADRIANd	Car Audio	32	30th September 2006 11:35 PM
Yamaha NS-1000X tweeters blown...whats the problem?	young_pup	Multi-Way	10	1st October 2005 07:41 PM
Yamaha P-2200 blown-up	xyonyx	Solid State	5	13th November 2004 07:54 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

24th November 2005, 06:42 PM	#2
MikeB diyAudio Member Join Date: Apr 2004 Location: Gütersloh	Possibly you overheated your outputdevices, bias to max might have been several amperes. Solder out one of the outputdevices and measure it. They are very likely to be shorted. In this case i would consider this amp a complete loss... sorry, Mike

25th November 2005, 07:43 PM	#3
namcir diyAudio Member Join Date: Jul 2005 Location: mid_east	thanks Mikeb for your reply: yes it is a big loss for me maybe i would be careful next time i tinker to my equipment. now i need a service manual to be able to service it properly could anybody help me acquire one? the model is yamaha pro-audio P7000s. please help

25th November 2005, 08:38 PM	#4
nikwal diyAudio Member Join Date: Aug 2005	My experiences with switch mode psu's says that if one component there fails MANY others probably will.. I've looked at a couple of yamaha schematics on pdf and they are'nt too complicated in the power amp , You could at least try to measure the transistors with mutimeter diode function, dont rely on it though! transistors may be "half" broken..

25th November 2005, 09:05 PM	#5
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi RICMAN, Yamaha normally has good protection networks and may be in shutdown mode. With any luck, you just killed the outputs, maybe drivers and more. In general, leave bias settings at factory default. This is more true with pro amps that have to be reliable. -Chris

25th November 2005, 09:08 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi RICMAN, Rereading, I see you have let the really expensive smoke out of the box. Could be fun, but not impossible to fix. To repair switching supplies, you need a way to vari the power so it doesn't just go bang if there is another fault. Another bipolar variable power supply may allow you to troubleshoot and fix the output stage. Wishing you luck with this. -Chris

26th November 2005, 02:21 PM	#8
adason diyAudio Member Join Date: Nov 2004 Location: troll in US	hi ricman i once had similar problem with an old akai power amp it had switching supply to make it light and sleak, which died after a while i replaced it with outside trafo/rectifiers and caps sounds great till now i would not waste time with switching power supply get the external and start replacing blown parts in the amp don't give up good luck e

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read