Replace Mark Levinson ML-2 with MJ15024/15025 need help

emergency · 15th April 2006, 07:46 PM

Dear all,

I have just replaced all the transistors(2N5686 and 2N5684) on my pairs of Mark Levinson ML-2 with MJ15024 and MJ15025(matched). The result is pretty stable, I am now trying to adjust the bias voltage to .56V(1A current to each transistor) as instructed by the service manual available on the web. But both units seems very hot, I cross check the bias voltage of other ML-2 with original transistor and they are around .4V....am I setting the bias voltage too high? Anyone have some idea this replacement?

Netlist · 15th April 2006, 07:58 PM

Did you measure both amps bias'ses when cold?

/Hugo

AVWERK · 15th April 2006, 09:32 PM

From memory, the 5686 combo are rated at 30 amps each and the 15024 combo at 15 amps each tranny.

Not sure if this has any effect with the original bias level?

David

EchoWars · 16th April 2006, 02:36 AM

Quote:

Originally posted by AVWERK
From memory, the 5686 combo are rated at 30 amps each

50 amps.

Those are two tough transistors.

emergency · 16th April 2006, 08:27 AM

So this means 1 amp current to the MJ15024/MJ15025 will not do any harm to the transistors?

Just compare with 2N5686/84, if the manual said the bais is .56V what voltage should I tune for the bias for MJ15024/25?

AndrewT · 16th April 2006, 09:04 AM

Hi,
are you saying that you have replaced 50A transistors with 15A transistors?

Or have you put in three times as many pairs?

Why do the 50A pairs need replacing?

djk · 16th April 2006, 06:29 PM

"Why do the 50A pairs need replacing?"

It's a 20W class A amplifier, after 30 years it could have just worn out and failed.

The MJ1502X parts should be close enough to work.

I would look at the amp with a scope, the new parts are a bit faster.

Generally, 1A per device (2A for the pair) is enough bias for class A in a push-pull amplifier to do 32W into 4 ohms (64W at 8 ohms).

emergency · 16th April 2006, 06:39 PM

Thanks for all the help.

It is because serving over 30 years, those 2N5686/84 were out of specs and some even show very small output.

I know that even Mark Levinson Dealers are using MJ15024/25 to replace 2N5686/64 as they are no longer available. That's why I make the choice to replace both units by matched pairs MJ15024/25.

Both units seems working very well after the replacement, but sounds pretty hash for the mean while. I think they need sometime to break-in.

My concern is whether I need to change the bias level. For using MJ15024/25.

Dennis

Elso Kwak · 16th April 2006, 06:41 PM

Those bad sounding ML2s get normally too hot to touch.

:bs:

EchoWars · 17th April 2006, 11:33 PM

Quote:

Originally posted by emergency
I know that even Mark Levinson Dealers are using MJ15024/25 to replace 2N5686/64 as they are no longer available.

It is still a current On-Semi device, and available through Digikey here...

Quote:

My concern is whether I need to change the bias level. For using MJ15024/25.

Dennis

I'd keep the same bias setting as the manufacturer recommends.

15th April 2006, 07:46 PM	#1
emergency diyAudio Member Join Date: Mar 2006 Location: Hong Kong	Replace Mark Levinson ML-2 with MJ15024/15025 need help Dear all, I have just replaced all the transistors(2N5686 and 2N5684) on my pairs of Mark Levinson ML-2 with MJ15024 and MJ15025(matched). The result is pretty stable, I am now trying to adjust the bias voltage to .56V(1A current to each transistor) as instructed by the service manual available on the web. But both units seems very hot, I cross check the bias voltage of other ML-2 with original transistor and they are around .4V....am I setting the bias voltage too high? Anyone have some idea this replacement?

16th April 2006, 09:04 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, are you saying that you have replaced 50A transistors with 15A transistors? Or have you put in three times as many pairs? Why do the 50A pairs need replacing? __________________ regards Andrew T.

16th April 2006, 06:41 PM	#9
Elso Kwak Banned Join Date: Dec 2001 Location: Zamboanga, City of Flowers, Mindanao	Hot Those bad sounding ML2s get normally too hot to touch. :bs:

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
Mark Levinson ¹27.5	Taifun	Solid State	101	14th March 2011 10:57 PM
Total newbie post - trying to replace ext. PS on vintage Mark Levinson ML-1 preamp	yamezxx	Power Supplies	3	26th August 2009 05:29 PM
Mark Levinson no:29	Snorkeltjes	Solid State	19	24th November 2007 01:18 PM
mark levinson	karma	Swap Meet	8	8th March 2003 02:42 AM
Mark Levinson ML2	arnach	Solid State	7	9th April 2001 05:36 PM


	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

15th April 2006, 07:58 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Did you measure both amps bias'ses when cold? /Hugo

15th April 2006, 09:32 PM	#3
AVWERK diyAudio Member Join Date: Jan 2004 Location: OC,Calif.	From memory, the 5686 combo are rated at 30 amps each and the 15024 combo at 15 amps each tranny. Not sure if this has any effect with the original bias level? David

16th April 2006, 08:27 AM	#5
emergency diyAudio Member Join Date: Mar 2006 Location: Hong Kong	So this means 1 amp current to the MJ15024/MJ15025 will not do any harm to the transistors? Just compare with 2N5686/84, if the manual said the bais is .56V what voltage should I tune for the bias for MJ15024/25?

16th April 2006, 06:29 PM	#7
djk diyAudio Member Join Date: Feb 2001 Location: USA	"Why do the 50A pairs need replacing?" It's a 20W class A amplifier, after 30 years it could have just worn out and failed. The MJ1502X parts should be close enough to work. I would look at the amp with a scope, the new parts are a bit faster. Generally, 1A per device (2A for the pair) is enough bias for class A in a push-pull amplifier to do 32W into 4 ohms (64W at 8 ohms).

16th April 2006, 06:39 PM	#8
emergency diyAudio Member Join Date: Mar 2006 Location: Hong Kong	Thanks for all the help. It is because serving over 30 years, those 2N5686/84 were out of specs and some even show very small output. I know that even Mark Levinson Dealers are using MJ15024/25 to replace 2N5686/64 as they are no longer available. That's why I make the choice to replace both units by matched pairs MJ15024/25. Both units seems working very well after the replacement, but sounds pretty hash for the mean while. I think they need sometime to break-in. My concern is whether I need to change the bias level. For using MJ15024/25. Dennis

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

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