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Old 30th December 2004, 02:03 AM   #1
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Default 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.
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Old 30th December 2004, 02:13 PM   #2
LBHajdu is offline LBHajdu  United States
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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.
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Old 30th December 2004, 10:30 PM   #3
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Default 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
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Old 31st December 2004, 02:06 AM   #4
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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.
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Old 18th February 2005, 12:59 AM   #5
remi is offline remi  China
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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
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Old 1st February 2009, 10:15 AM   #6
hifiboy is offline hifiboy  Germany
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Unhappy 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
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Old 1st February 2009, 10:36 AM   #7
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http://www.audio-circuit.dk/images/s...7-5-pwr-sm.pdf
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Old 1st February 2009, 03:57 PM   #8
lineup is offline lineup  Sweden
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It is a terrible amplifier.
Looking at the schematics in service manual.

Shows the cascode is 'roender-style' with current source to bias.
Attached Images
File Type: png marklev_input.png (40.2 KB, 775 views)
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Old 1st February 2009, 05:10 PM   #9
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I can email you the schematics if you send me your address.
You have it blocked in DIY
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Old 1st February 2009, 06:13 PM   #10
lineup is offline lineup  Sweden
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Thanks.
I downloaded the PDF from Jacco's link. That's well enough.
Regards.
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