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need some help on my Mark Levinson No23
need some help on my Mark Levinson No23
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Old 19th March 2015, 11:02 AM   #1
loveaudio is offline loveaudio  Australia
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Default need some help on my Mark Levinson No23

any one here work on one of these before ?
i just need to know the resistor next to the x2 rated cap on the front panel board , what it job in the front panel circuit ? mine is just smoked , but i need to find out what cause it to overheat .
attathed is the pictures of the board and resistor in question.
thanks
Peter
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File Type: jpg Mark no23.jpg (220.6 KB, 163 views)
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Old 19th March 2015, 08:32 PM   #2
llwhtt is offline llwhtt  United States
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I have one sitting here that I just finished last week. The resistor is a 11kohm/2 Watt carbon comp that appears to just power the front panel LED. That's all I can tell by just looking behind the front panel. I am NOT going to disassemble it again, too much time involved.

Craig
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Old 19th March 2015, 08:59 PM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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11k? that is an odd value. Not a discoloured 12k?
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Old 19th March 2015, 09:17 PM   #4
llwhtt is offline llwhtt  United States
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It is definitely 11k, brown, brown, orange, gold, looks brand new, big two Watt CC.

Craig
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Old 19th March 2015, 09:42 PM   #5
srh is offline srh  New Zealand
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11k is a standard value in the E24 range and above.
Steve.
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Old 19th March 2015, 11:09 PM   #6
loveaudio is offline loveaudio  Australia
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Thanks Guys.
yes the resistor is 11K as Graig have said ( brown-brown-Orange ).
this amp first fired some of the 4700pf x2 rated caps in near by area with this is resistor . i changed those and now this resistor firer , hence my reason to findout what cause and what this resistor function in this board .

also Graig. did you have to adjust the bias on this amp after you done the repair ?
Cheers
Peter
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Old 19th March 2015, 11:47 PM   #7
llwhtt is offline llwhtt  United States
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This amp came to me with shipping damage and that's all I repaired. Replaced all 12 of the big PCB mounted electrolytic capacitors (because several broke off), transistor insulators, and thermal compound. I did NOT adjust the idle current because I couldn't find a reliable source on how to do so. I measured THD at 20, 200, 2k, and 20kHz at 2, 20, 200 Watts all were in .00x range or so and it idles only warm so I figured I'd just leave it. Did I mention these are a PITA to work on?

Craig

Last edited by llwhtt; 19th March 2015 at 11:51 PM.
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Old 19th March 2015, 11:59 PM   #8
loveaudio is offline loveaudio  Australia
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Quote:
Originally Posted by llwhtt View Post
This amp came to me with shipping damage and that's all I repaired. Replaced all 12 of the big PCB mounted electrolytic capacitors (because several broke off), transistor insulators, and thermal compound. I did NOT adjust the idle current because I couldn't find a reliable source on how to do so. I measured THD at 20, 200, 2k, and 20kHz at 2, 20, 200 Watts all were in .00x range or so and it idles only warm so I figured I'd just leave it. Did I mention these are a PITA to work on?

Craig
Thanks Graig.
indeed it is very time consuming to work on this amp . too many screws to take off
nice to know you replace the caps . can you kindly let me know where you souse the caps ? i might consider change them on mine too .
i ask about the bias is that I can see after i run mine for around 15 mins one side of the heatshink seem a bit warmer than the other side therefore i think one channel bias might be off a bit ? no ?
cheers
Peter
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Old 20th March 2015, 12:32 AM   #9
llwhtt is offline llwhtt  United States
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In order to replace those capacitors the PCB needs to removed from the heat sink. All of the TO-3 transistors are soldered to the double-sided board thru eyelets making them very hard to remove without damaging the board. So unless you have a very strong desoldering station I would leave the caps alone unless the PCB needs to be removed for other reasons.

I used the only caps I could find in the short time I had to do the job. They were Nichicons from Mouser. The 680uf and 330uf 100v caps had to be increased to 200v as that's all I could find. The original caps are long gone.

Craig
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Old 31st March 2020, 09:53 PM   #10
tiefbassuebertr is offline tiefbassuebertr  Germany
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for additional pictures check out this thread:
Mark Levinson No23 repair help
who can upload the schematic ?
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