Mark Levinson No 27 Problem

johnsciolino · 30th December 2004, 02:03 AM

I am having intermittant problem with a No27 Levinson.
Breaker trips on front and emits a buzz in speaker on one channel.
However, if I ramp up with variac to 50v one channel has alot of DC offset (300mv) and after about a minute it drops to 10mv. At that time I can continue to ramp voltage up to 120v without tripping breaker. The amp plays fine after doing this startup procedure. When power is removed it goes back to the same problem on restart.
Could this be a bad cap? Its difficult to trace because using the variac seems to temporarily cure the problem before I can start troubleshooting.

LBHajdu · 30th December 2004, 02:13 PM

Do you happen to know how this amp handles inrush current limiting, it sounds like the inrush limiter may not be working. I would suspect they use a triac, however I have never seen the schematic of this amp.

johnsciolino · 30th December 2004, 10:30 PM

Files too big to post so heres the temp link to download.
Just got Madrigal to email these to me today.

http://www.munsonandbryan.com/downlo...schematics.pdf

http://www.munsonandbryan.com/downlo...fOperation.pdf

http://www.munsonandbryan.com/downlo..._procedure.PDF

johnsciolino · 31st December 2004, 02:06 AM

OK,
Got the schematics and bypassed the relay.
Its a short somewhere in the input. With the unit bypassed I get rail voltage at speaker output at full voltage but
its not blowing rail fuses probably due to the open circuit at speakers.

remi · 18th February 2005, 12:59 AM

Hello johnsciolino
Someone has asked me to mend their ML27, so that I am looking for the ML27 schematics.
That links site doesn't have it. Can you send it to me?
If you can help me I really thank.
My E-mail remi_gao@126.com

Regards
Remi

hifiboy · 1st February 2009, 10:15 AM

Hi,

I have a problem with the ML27: one channel is dead when the cinch input is connected. When the AES input is connected there is a 50 Hz hum. Anyone can help? Anyone who can send me the schematics?

Hifiboy

jacco vermeulen · 1st February 2009, 10:36 AM

http://www.audio-circuit.dk/images/s...7-5-pwr-sm.pdf

lineup · 1st February 2009, 03:57 PM

It is a terrible amplifier.
Looking at the schematics in service manual.

Shows the cascode is 'roender-style' with current source to bias.

johnsciolino · 1st February 2009, 05:10 PM

I can email you the schematics if you send me your address.
You have it blocked in DIY

lineup · 1st February 2009, 06:13 PM

Thanks.
I downloaded the PDF from Jacco's link. That's well enough.
Regards.

30th December 2004, 02:03 AM	#1
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	Mark Levinson No 27 Problem I am having intermittant problem with a No27 Levinson. Breaker trips on front and emits a buzz in speaker on one channel. However, if I ramp up with variac to 50v one channel has alot of DC offset (300mv) and after about a minute it drops to 10mv. At that time I can continue to ramp voltage up to 120v without tripping breaker. The amp plays fine after doing this startup procedure. When power is removed it goes back to the same problem on restart. Could this be a bad cap? Its difficult to trace because using the variac seems to temporarily cure the problem before I can start troubleshooting.

30th December 2004, 10:30 PM	#3
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	No 27.5 Manual, Schematics and Test procedure Files too big to post so heres the temp link to download. Just got Madrigal to email these to me today. http://www.munsonandbryan.com/downlo...schematics.pdf http://www.munsonandbryan.com/downlo...fOperation.pdf http://www.munsonandbryan.com/downlo..._procedure.PDF

1st February 2009, 10:15 AM	#6
hifiboy diyAudio Member Join Date: Apr 2004 Location: Munich	ML27 schematics Hi, I have a problem with the ML27: one channel is dead when the cinch input is connected. When the AES input is connected there is a 50 Hz hum. Anyone can help? Anyone who can send me the schematics? Hifiboy

1st February 2009, 10:36 AM	#7
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	http://www.audio-circuit.dk/images/s...7-5-pwr-sm.pdf __________________ Looks like Sponge Bob has killed another thread.

1st February 2009, 06:13 PM	#10
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Thanks. I downloaded the PDF from Jacco's link. That's well enough. Regards. __________________ lineup


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30th December 2004, 02:13 PM	#2
LBHajdu diyAudio Member Join Date: Feb 2002 Location: NY, USA	Do you happen to know how this amp handles inrush current limiting, it sounds like the inrush limiter may not be working. I would suspect they use a triac, however I have never seen the schematic of this amp.

31st December 2004, 02:06 AM	#4
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	OK, Got the schematics and bypassed the relay. Its a short somewhere in the input. With the unit bypassed I get rail voltage at speaker output at full voltage but its not blowing rail fuses probably due to the open circuit at speakers.

18th February 2005, 12:59 AM	#5
remi diyAudio Member Join Date: Nov 2004 Location: guangzhou	Hello johnsciolino Someone has asked me to mend their ML27, so that I am looking for the ML27 schematics. That links site doesn't have it. Can you send it to me? If you can help me I really thank. My E-mail remi_gao@126.com Regards Remi

1st February 2009, 05:10 PM	#9
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	I can email you the schematics if you send me your address. You have it blocked in DIY

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