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Ever happened to you??

dj_AmTraX

dj_AmTraX

Super Member
Banned
This morning I turned on the MC2000 as I do every morning. MX119 connect power turn on cable to MC2000. Five seconds into it I hear scratching sound from left speaker followed by loud pops. I looked at the MC2000 and saw sparks from tube KT88 V7L & V6L. Then the left speaker sounded like firecrackers going off. I immediately turned off the amp. I then saw smoke from those tubes. I now smell burned circuit board. After everything cooled down I pulled the left channel tubes for inspection. I am new to tubes, but did not see anything that is obviously wrong with them. I am afraid to turn it back on with my expensive speakers connect to it. I have to test with my MC352 to see any damage to my speakers.

Please help!
 
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Your speakers should be fine. Contact the dealer you bought it from and ask them how they want to proceeded with the repair. Sounds like you smoked a diode or resistor when the tube shorted.

Thanks,
Ron-C
 
Thank you for your quick response. Sorry that I emailed you with the same question. I was just in a panic.

Why would the tubes short out? I didn't move or change anything. If it happens again in the future and the amp was unattended, will the amp catch fire and burn my house down?

Do I need a new tube set?
 
WOW!
Not good...& after only 4 days...:tears:
The guys from Audio Classics will take care of you, rest assured.
Hope you have a spare amp, there's never a good time for a breakdown, but the holidays are a especially bad time to be without tunes!
 
When a kt88 dies is it common to bring down part of the circuit with it? Should we be replacing our output tubes on a regular basis as a precaution?
 
I had the same thing happen to me a few months ago. I had a case of
"arc over" and it happened during the initial warm up....just like your experience. I was able to turn the amp off quickly before anything ugly happened.

The KT 88's only had a few hours on them and had worked fine up to that point! I'm now using the McRussian and Penta Labs KT 88's and have not had any issues.

Good luck with your repair and hope you do not have any more troubles.
Robert
 
I can't believe that the main board got fried. Am I suppose to change the board each time this happens??? It sounds like a common thing for KT88s.

I'm glad that I brought it from Audio Classics. Mike is going to take care of everything for me.
 
my 2102 did the same thing a while back and again recently.

new tubes and $1.00 in diodes fixed it fine. Mc (or any other manu.) cant control how a tube will behave. Some tubes will last years others minutes.

PArt of the fun of tube gear. Good screening and burning in of tubes by your retailer of choice is the best antidote.
 
Ron,

The board did go. Is there a reason why the board was burned? Could there be another problem???
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The resistor came off the solider.
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Update:

All fixed within one week. Audio Classics sent me brand new replacement tubes and main circuit board. Everything plays nicely with my new Gold Lion KT88. Anyone want to buy some new stock tubes?
 
Seems like this is rather common for KT88 (at least for me). It happened to me last year and the resistor under the power tube socket got burnt, a replacement of a new resistor and a new tube fixed the problem, luckily the circuit board was ok. BTW, I am using MC275 CE.

And it happended to me last week with one tube die ( i can hear something loose inside the tube ) so I replaced the whoel quad just in case, the remaining 3 would be as a "spare"!!

As others have said, can't really control how the tube behave! Enjoy the music!
 
Why do I keep reading such threads when I am about to take delivery of my first tube amp????? :sigh:

In fact it's about to arrive in an hour. :banana:
 
I touch wood before I say this.

I use 6550's in my 2xMC2102's and have not had a problem in 3 years.
 
Wonder if McIntosh intends to "trickle down" the sentry monitoring which is a feature of the MC2301's?:scratch2:

SENTRY MONITOR TUBE PROTECTION
The output tubes have limits for the maximum amount of power they can handle. The MC2301 output stage and power supply have been designed to allow high current flow into properly matched load impedances. If, however, a short circuit or very low value of load impedance is applied to the output of the MC2301, destructive current levels could be reached. The Sentry Monitor circuit prevents this. The circuit senses the dynamic operating time, voltage, and current of the amplifier output tubes and confines it to nondestructive levels. Sentry Monitor does not limit the power output available from the amplifier. Sentry Monitor also protects the entire amplifier circuitry in the event that a failed Output Tube causes higher than normal current to flow. To prevent destruction, the MC2301 power is turned off. The protection mode is indicated by the flashing of the red standby indicator on the front panel. The Protect Mode is reset to normal operation by cycling the MC2301 power off and then back on with the POWER switch.


I know first hand this sentry monitor works -- or at least I believe it kicked in - as had one tube (GL Reissue) that would cause the left amp to go into shutdown (I decided to test all 15 remaining tubes on my tube tester -- they were fine). The one which caused the amp to shutdown failed several tests on my tube tester.

By the way, I recommend having spares -- I have 12 KT88's in reserve.
 
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