I did a stupid thing... (Nad C320 red light)

skouliki · 21st July 2011, 08:46 PM

I was reading the Nad c320 service manual and decided to do the alighment procedure. Everything was going well until i shorted TP2 and R242 with the pin of my dmm....a spark came out the resistor, and now the led of the amp stays red instead going to green, plus the heatsinks of the drivers are getting really hot. I havent got any background in electronics, i m just doing really basic stuff: changing capacitors and resistors etc. I included a link to the service manual. If somebody has any insight on how to repair this little amp i would be grateful

nad_c-320_sm_[ET].pdf - 4.0 MB

Tekko · 21st July 2011, 09:53 PM

Take it to a repair place, as you likely caused most of the transistors on the board for that channel to blow.

Outputs are guranteed to be gone, same with the drivers.

FenderBender11 · 21st July 2011, 10:21 PM

Replacing all semiconductor which you think it might have affected is a good start.

skouliki · 10:48 PM

Thanks for your input guys. For the past 6 months i was upgrading the parts of this amp and was very pleased so far...changed electrolytics to Black gate and Elna cerafine,ceramics to silver mica, carbon resistors to metal film, polyester caps to mkp1837. The amp was totally transformed. Anyway, next time i'll be more careful. Good thing i have spares of the output transistors, but i think it would be hard to find replacements for sd669/sb649. Are there any suitable replacements for these?

WuYit · 21st July 2011, 10:54 PM

BD139/140

nigelwright7557 · 11:23 PM

Confuscious he say if it its working leave well alone !

Done it myself, dropped my jewellers screwdriver while tweaking a pot.
Should have bought a plastic tweeker !

skouliki · 11:42 PM

Quote:

Originally Posted by nigelwright7557

Confuscious he say it its working leave well alone !

Done it myself, dropped my jewellers screwdriver while tweaking a pot.
Should have bought a plastic tweeker !

So true! And i have to add that only 3 hours of sleep after the night shift seriously impairs decision making and stability of hands.

destroyer X · 22nd July 2011, 08:22 AM

You must send it to a skilled repairman if you do not feel yourself good to to that.

After night shift we are good for the bed only.

regards,

Carlos

phonomac · 22nd July 2011, 08:53 AM

Hi there,
Second source SB649/SD669, manufactured by Hi-Sincerity Microelectronics Corp of Taiwan, are available from eBay seller audiowind-2005.

They are marked as HSB649A and HSD669A, hFE grade C, and as far as I can tell from basic measuring apparatus meet the spec. The datasheet is available from the Hi-Sincerity website.

No connection, just a customer.

Hope this helps.

Regards

Angus

skouliki · 21st August 2011, 12:09 AM

Today i finally managed to replace the output transistors and the drivers but the amp still refuses to go out of protection mode.... any thoughts?

21st July 2011, 08:46 PM	#1
skouliki diyAudio Member Join Date: Aug 2010	I did a stupid thing... (Nad C320 red light) I was reading the Nad c320 service manual and decided to do the alighment procedure. Everything was going well until i shorted TP2 and R242 with the pin of my dmm....a spark came out the resistor, and now the led of the amp stays red instead going to green, plus the heatsinks of the drivers are getting really hot. I havent got any background in electronics, i m just doing really basic stuff: changing capacitors and resistors etc. I included a link to the service manual. If somebody has any insight on how to repair this little amp i would be grateful nad_c-320_sm_[ET].pdf - 4.0 MB

21st July 2011, 09:53 PM	#2
Tekko diyAudio Member Join Date: Jan 2005	Take it to a repair place, as you likely caused most of the transistors on the board for that channel to blow. Outputs are guranteed to be gone, same with the drivers. __________________ The point of life is to build atleast one audio amplifier before you die.

21st July 2011, 10:26 PM	#4
skouliki diyAudio Member Join Date: Aug 2010	Thanks for your input guys. For the past 6 months i was upgrading the parts of this amp and was very pleased so far...changed electrolytics to Black gate and Elna cerafine,ceramics to silver mica, carbon resistors to metal film, polyester caps to mkp1837. The amp was totally transformed. Anyway, next time i'll be more careful. Good thing i have spares of the output transistors, but i think it would be hard to find replacements for sd669/sb649. Are there any suitable replacements for these? Last edited by skouliki; 21st July 2011 at 10:48 PM.

21st July 2011, 11:16 PM	#6
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	Confuscious he say if it its working leave well alone ! Done it myself, dropped my jewellers screwdriver while tweaking a pot. Should have bought a plastic tweeker ! __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software. Last edited by nigelwright7557; 21st July 2011 at 11:23 PM.

22nd July 2011, 08:22 AM	#8
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	Protection circuit was damaged....Q21 gone... and others may be dead too You must send it to a skilled repairman if you do not feel yourself good to to that. After night shift we are good for the bed only. regards, Carlos __________________ Try to build an amplifier folks ... it is pure adrenaline!.. when not work first time, then becomes a nice challenge...and we usually overcome the trouble... and we feel very well to be mastering the machine.


	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

21st July 2011, 10:21 PM	#3
FenderBender11 diyAudio Member Join Date: Jun 2011	Replacing all semiconductor which you think it might have affected is a good start.

21st July 2011, 10:54 PM	#5
WuYit Banned Join Date: Oct 2010	BD139/140

22nd July 2011, 08:53 AM	#9
phonomac diyAudio Member Join Date: Mar 2011	Hi there, Second source SB649/SD669, manufactured by Hi-Sincerity Microelectronics Corp of Taiwan, are available from eBay seller audiowind-2005. They are marked as HSB649A and HSD669A, hFE grade C, and as far as I can tell from basic measuring apparatus meet the spec. The datasheet is available from the Hi-Sincerity website. No connection, just a customer. Hope this helps. Regards Angus

21st August 2011, 12:09 AM	#10
skouliki diyAudio Member Join Date: Aug 2010	Today i finally managed to replace the output transistors and the drivers but the amp still refuses to go out of protection mode.... any thoughts?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

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
Nad c320 service manual	crazy_bob_uk	Solid State	9	20th April 2011 07:51 PM
Help me to fix my nad c320: need a res value	hehe31	Digital Source	6	4th February 2011 06:03 PM
another NAD 304 whit the red light on...	al37perez	Solid State	5	8th May 2010 02:24 PM
nad c320	reddish75	Solid State	3	16th September 2008 02:05 PM
Nad C320 Psu?	skenwrick	Solid State	0	3rd February 2006 02:37 PM

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