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Mark Levinson 336 blowing fuses in home
Mark Levinson 336 blowing fuses in home
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Old 3rd August 2016, 10:14 AM   #11
MIKEVO is offline MIKEVO  United Kingdom
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Quote:
Originally Posted by ColinA View Post
Is this not like fitting a bigger fuse because it keeps blowing?

The FIRST thing to do is find out why they were overloaded.
No, I said use the correct nichrome wire, which is acting as a heating element and not like a fuse. It is not overloaded.

There is no fault with the amp, its just over time with constant powering on and off the nichrome wire degrades, just like a lightbulb filament.

An overspecced resistor will work, but will offer little or no protection if the amp develops a fault.
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Old 3rd August 2016, 11:40 AM   #12
willcycle is offline willcycle  United States
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I would say a 22W wire wound resistor should work. When I recapped one of my Krell KSA250 amplifiers I replaced the four power supply caps with 100K uF units (original was 40K). There are four 7.5 ohm 20 watt sand resistors as part of the soft start circuit which promptly blew. Granted the amp was in use for approximately 20 years before recap so I am sure they were weakened. I replaced them with 22 watt wire wound resistors and the amp has been functioning fine for the last four years. The resistors only need to conduct the high inrush current for a very short period of time before they are switched out by the soft start circuit.
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Old 3rd August 2016, 11:41 AM   #13
wmns is offline wmns
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Fully agree. I suspect that the wire just degraded after time. Would be nice to know whether these 3 resistors are in parallel or series or just separate switched by time relays. I have no schematics of this amp.
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Old 3rd August 2016, 05:07 PM   #14
llwhtt is offline llwhtt  United States
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Why can't you use the good amp to measure and compare?

Craig
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Old 4th August 2016, 06:08 AM   #15
wmns is offline wmns
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I measured and found that the 3 resistors were in parallel. Bridged them by 4 1 ohm 100 W resistors in series, which I connected outside the amp and the amp is now switching on perfectly. The resistors don't even get warm and they fit nicely under the amp. Thanks for all your comments.
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Old 4th August 2016, 09:07 AM   #16
Bonsai is offline Bonsai  Europe
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Good result. I am doing something similar on my e-Amp. Without the soft start, the fuse and/or the mains trips every time. I have about 150mF in total and a 1kVA transformer.
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Old 4th August 2016, 09:39 AM   #17
MIKEVO is offline MIKEVO  United Kingdom
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Originally Posted by wmns View Post
I measured and found that the 3 resistors were in parallel. Bridged them by 4 1 ohm 100 W resistors in series, which I connected outside the amp and the amp is now switching on perfectly. The resistors don't even get warm and they fit nicely under the amp. Thanks for all your comments.
They should be good for a few thousand years.
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Old 15th July 2018, 11:21 PM   #18
renjy651 is offline renjy651  United States
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You cannot use any surge resistors for Mark Levinson 331/332/333/334/335/336/33H. ML uses special surge resistors that have to meet High voltage rating Joules about 290 Working voltage at 1090V. Nichrome wire wounded to get 10 Ohms either 10 watt or 15 watt. I send the new Levinson resistors to Reidon to make a better one, They made the SP-1976 10 Ohms 15 watts. and coated with Silicone. Redon eng recommended It. In case the wire breaks it will not fly around and hit any board. The surge resistors are there to protect the amp. THIS PART IS SPECIAL ORDERED AND MADE IN USA.
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Old 15th July 2018, 11:33 PM   #19
renjy651 is offline renjy651  United States
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MARK LEVINSON OLD AND NEW SURGE RESISTORS.
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Old 16th July 2018, 11:37 AM   #20
jaycee is offline jaycee  United Kingdom
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Pff, over engineered audiophile nonsense from ML. They could just as well have used ordinary wirewound resistors with a thermal fuse sandwiched between them for protection.

Wirewounds will also blow open if they overheat, the ceramic body will probably crack but they certainly wont fail as a short
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